Judgment of 25 September 1997

Document Number
092-19970925-JUD-01-00-EN
Document Type
Date of the Document
Document File
Bilingual Document File

INTERNATIONAL COURT OF JUSTICE

REPORTS OF JUDGMENTS,
ADVISORY OPINIONS AND ORDERS

CASE CONCERNING
THE GABCIKOVO-NAGYMAROS PROJECT

(HUNGARYISLOVAKIA)

JUDCMENT OF 25 SEPTEMBER 1997

COUR INTERNATIONDE JUSTICE

RECUEIL DES ARRÊTS,
AVIS C:ONSULTATIFS ET ORDONNANCES

AFFAIRE RELATIVE AU PROJET

GA.BCIKOVO-NAGYMAROS

(HONGRIEISLOVAQUIE)

ARRÊT DU 25 SEPTEMBRE 1997 Official citati:n
GabCikovo-NagymarosProject (HungarylSlovakia),
Judgment, 1.C.J. Reports1997, p. 7

Mode officiede citation:
Projet GabCikovo-Nagymaros (HongrielSlovaquie),
arrêt,C.I.J. Recueil1997, p. 7

Sales number
ISSN 0074-4441 Node vente: 692

ISBN 92-1-070757-5 25 SEPTEMBER 1997

JUDGMENT

GABC~KOVO-NACYMAROS PROJECT

(HUNGARYISLOVAKIA)

PROJET GABCIKOVO-NAGYMAROS

(HONGRIEISLOVAQUIE) INTERNATIONAL COURT OF JUSTICE

1997 YEAR 1997
25 September
General List
No. 92 25 September1997

CASE CONCERNING

THE GABC~KOVO-NAGYMAROS PROJECT

(HUNGARYISLOVAKIA)

Treaty of 16 September 1977 concerning the construction and operation of
the GabCikovo-Nugymaros Systenz of Locks - "Related instruments".
Suspension and abandonment by Hungary, in 1989, oj'works on the Project

- Applicability of the Vienna Convention of 1969 on the Law of Treaties -
Law of treaties and law of State responsibility - Stute of necessity as a ground
jor precluding the wrongfulness of an act - "Essential interest" of the State
committing the act - Environment - "Grave und imminent peril" - Act

having to constitute the "only means" of saj&guardingthe interest threatened -
State having "contributed to the occurrence of the state of necessity".
Czechoslovakia:~proceeding, in November 1991, to "Variant C" andputting
into operation, from October 1992, this Variant - Arguments drawn from a
proposed principle of approximate application - Respect for the limits of the

Treaty - Right to an equitahle and reasonable share of rhe resources of an
international wutercourse - Commission of a wrongful act andprior conduct of
a prepararory character - Obligation to mitigate damages - Principle con-
cerning only the calculation of damages - Countermeasures - Response to an

internationally wrongful act - Proportionality - Assumption of unilateral
control of a shared resource.
Notification by Hungary, on 19 May 1992, of the fermination of the 1977
Treaty and reluted instruments - Legal efjrects - Matter falling within the law

of treaties - Articles 60 to 62 of the Vienna Convention on the Law of Trearies
- Customury law - lmpossihility of performance - Permanent disappearance
or destruction of an "object" indispensablefor execution - Impossibility of prr-
formance resulting from the hreach, by the party invoking il, of an obligation
under the Treaty - Fundamental change of circumstances - Essential basis of

the consent of the parties - Extent of obligations still to be performed - Sta-
bility of treaty relations - Material breach of the Treaty - Date on which the
breach occurred and date of notijïcation of termination - Victim of a breach
having itselfcommitted a prior breach of the Treaty - Emergence of new norms
of environmental law - Sustainable development - Treaty provisions permit-8 GABC~KOVO-NAGYMA PRROJSCT (JUDGMENT)

ting the parties, by mutual consent, to take account of those norms - Repudia-
tion of the Treaty - Reciprocal non-compliance - Integrity of the rule pacta
sunt servanda - Treaty remaining inforce until terminated by mutual consent.

Legal consequences of the Judgment of the Court - Dissolution of Czecho-

slovakia - Article 12 of the Vienna Convention of 1978on Succession of States
in respect of'Treaties - Customary laiv - Succession of States without effect
on a treaty creating rights and obligations "attaching" to the territory -
Irregular state of uffairs as a result of failure of both Parties to comply with
their treaty obligations - Ex injuria jus non oritur - Objectives of the Treaty
- Obligations overtaken by events - Positions adopted by the parties after

conclusion of the Treaty - Goodfaith negotiations - Effects of the Project on
the environment - Agreed solution to befound by the Parties - Joint régime
- Reparation for arts committed by both Parties - Co-operation in the use of
shared water resources - Damages - Succession in respect of rights and obli-
gations relating to the Project - Intersecting ivrongs- Settlement of accounts
for the construction of the works.

JUDGMENT

Present: President SCHWEBEL V;ice-President WEERAMANTRJY u; ges ODA,

BEDIAOUIG , UILLAUMR EA, NJEVA,HERCZEGHS ,HI, FLEISCHHAUER,
KOROMAV , ERESHCHET PINR, RA-ARANGUREN, KOOIJMANS R,EZEK;
Judge ad hoc SKUBISZEW ;SKeIgistrar VALENCIA-OSPINA.

In the case concerning the GabCikovo-Nagymaros Project,

between

the Republic of Hungary,
represented by

H.E. Mr. Gyorgy Szénasi,Ambassador, Head of the International Law
Department, Ministry of Foreign Affairs,
as Agent and Counsel;

H.E. Mr. DénesTomaj, Ambassador of the Republic of Hungary to the
Netherlands,

as Co-Agent ;
Mr. James Crawford, Whewell Professor of International Law, University of
Cambridge,
Mr. Pierre-Marie Dupuy, Professor at the University Panthéon-Assas

(Paris II) and Director of the Institut des hautes études internationales
of Paris,
Mr. Alexandre Kiss, Director of Research, Centre national de la recherche
scientifique (retd.),
Mr. Laszlo Valki, Professor of International Law, Eotvos Lorand Univer-
sity, Budapest, GABCIKOVO-NAGYMAROSPROJECT(JUDGMENT)

Mr. Boldizsar Nagy, Associate Professor of International Law, Eotvos
Lorand University, Budapest,
Mr. Philippe Sands, Reader in International Law, University of London,
School of Oriental and African Studies, and Global Professor of Law,
New York University,

Ms Katherine Gorove, consulting Attorney,
as Counsel and Advocates;
Dr. Howard Wheater, Professor of Hydrology, Imperia1College, London,
Dr. Gabor Vida, Professor of Biology, Eotvos Lorand University, Budapest,

Member of the Hungarian Academy of Sciences,
Dr. Roland Carbiener, Professor emeritus of the University of Strasbourg,
Dr. Klaus Kern, consulting Engineer, Karlsruhe,
as Advocates;
Mr. Edward Helgeson,

Mr. Stuart Oldham,
Mr. PéterMolnar,
as Advisers;
Dr. Gyorgy Kovacs,
Mr. Timothy Walsh,

Mr. Zoltan Kovacs,
as Technical Advisers ;
Dr. Attila Nyikos,

as Assistant ;
Mr. Axe1Gosseries, LL.M.,

as Translator ;
Ms Éva Kocsis,
Ms Katinka Tompa,

as Secretaries,
and

the Slovak Republic,
represented by

H.E. Dr. Peter Tomka, Ambassador, Legal Adviser of the Ministry of For-
eign Affairs,
as Agent;

Dr. Vaclav Mikulka, Member of the International Law Commission,
as Co-Agent, Counsel and Advocate;

Mr. Derek W. Bowett, C.B.E., Q.C., F.B.A., Whewell Professor emeritus of
International Law at the University of Cambridge, former Member of the
International Law Commission,
as Counsel ;
Mr. Stephen C. McCaffrey, Professor of International Law at the University
of the Pacific, McGeorge School of Law, Sacramento, United States of

America, former Member of the International Law Commission,
Mr. Alain Pellet, Professor at the University of Paris X-Nanterre and at the Institute of Political Studies, Paris, Member of the International Law
Commission,
Mr. Walter D. Sohier, Member of the Bar of the State of New York and of
the District of Columbia,
Sir Arthur Watts, K.C.M.G., Q.C., Barrister, Member of the Bar of England
and Wales,
Mr. Samuel S. Wordsworth, avocat à la cour d'appel de Paris, Solicitor of
the Supreme Court of England and Wales, Frere Cholmeley, Paris,

as Counsel and Advocates;
Mr. Igor Mucha, Professor of Hydrogeology and Former Head of the
Groundwater Department at the Faculty of Natural Sciencesof Comenius
University in Bratislava,
Mr. Karra Venkateswara Rao, Director of Water Resources Engineering,
Department of Civil Engineering, City University, London,

Mr. Jens Christian Refsgaard, Head of Research and Development, Danish

Hydraulic Institute,
as Counsel and Experts;
Dr. Cecilia KandraCova, Director of Department, Ministry of Foreign
Affairs,
Mr. Ludëk Krajhanzl, Attorney at Law, Vyroubal Krajhanzl Skacel and

Partners, Prague,
Mr. Miroslav LiSka, Head of the Division for Public Relations and Exper-
tise, Water Resources Development State Enterprise, Bratislava,

Dr. Peter VrSansky, Minister-Counsellor, Chargé d'affaires a.i.o ,f the
Embassy of the Slovak Republic, The Hague,
as Counsellors ;

Miss Anouche Beaudouin, allocataire de recherche at the University of
Paris X-Nanterre,
Ms Cheryl Dunn, Frere Cholmeley, Paris,
Ms Nikoleta GI!ndova, attaché, Ministry of Foreign Affairs,
Mr. Drahoslav Stefanek, attaché, Ministry of Foreign Affairs,
as Legal Assistants,

composed as above,
after deliberation,

delivers thefollowing Judgment ;

1. By a letter dated 2 July 1993, filed in the Registry of the Court on the
same day, the Ambassador of the Republic of Hungary (hereinafter called
"Hungary") to the Netherlands and the Chargéd'affaires ad interim of the Slo-
vak Republic (hereinafter called "Slovakia") to the Netherlands jointly notified
to the Court a Special Agreement in English that had been signed at Brussels
on 7 April 1993and had entered into force on 28 June 1993,on the date of the
exchange of instruments of ratification.
2. The text of the Special Agreement reads as follows: GABcIKOVO-NAGYMAROS PROJECT (JUDGMENT)

"The Republic of Hungary and the Slovak Rcpublic,

Considering that differences have arisen between the Czech and Slovak
Federal Republic and the Republic of Hungary regarding the implementa-
tion and the termination of the Treaty on the Construction and Operation
of the Gabtikovo-Nagymaros Barrage System signed in Budapest on
16September 1977and related instruments (hereinafter referred to as 'the
Treaty'), and on the construction and operation of the 'provisional solu-
tion';
Beuring in nlind that the Slovak Republic is one of the two successor
States of the Czech and Slovak Federal Republic and the sole successor
State in respect of rights and obligations relating to the GabCikovo-Nagy-

maros Project ;
Recognizing that the Parties concerned have been unable to settle these
differences by negotiations;
Huving in rnind that both the Czechoslovak and Hungarian delegations
expressed their commitment to submit the differences connected with the
GabCikovo-Nagymaros Project in al1 its aspects to binding international

arbitration or to the International Court of Justice;
Desiring that these differences should be settled by the International
Court of Justice;
Reculling their commitment to apply, pending the Judgment of the
International Court of Justice, such a temporary watermanagement régime
of the Danube as shall be agreed between the Parties;

Desiring further to define the issues to be submitted to the International
Court of Justice.
Have agreed as follows :

Article I

The Parties submit the questions contained in Article 2 to the Interna-
tional Court of Justice pursuant to Article 40, paragraph 1, of the Statute
of the Court.

Article 2
(1) The Court is requested to decide on the basis of the Treaty and rules
and principles of general international law. as well as such other treaties as
the Court may find applicable,

(a) whether the Republic of Hungary was entitled to suspend and subse-
quently abandon, in 1989, the works on the Nagymaros Project and
on the part of the GabCikovo Project for which the Treaty attributed
responsibility to the Republic of Hungary:
(b) whether the Czech and Slovak Federal Republic was entitled to pro-
ceed, in November 1991,to the 'provisional solution' and to put into
operation from October 1992this system, described in the Report of
the Working Group of Independent Experts of the Commission of
the European Communities, the Republic of Hungary and the Czech
and Slovak Federal Republic dated 23 November 1992(damming up
of the Danube at river kilometre 1851.7 on Czechoslovak territory

and resulting consequences on water and navigation coufse);12 GABC~KOVO-NAGYMAROSPROJECT(JUDGMENT)

(c) what are the legal effects of the notification, on 19 May 1992,of the
termination of the Treaty by the Republic of Hungary.
(2) The Court is also requested to determine the legal consequences,

including the rights and obligations for the Parties, arising from itsudg-
ment on the questions in paragraph 1 of this Article.
Article 3

(1) Al1questions ofprocedure and evidenceshall be regulated in accord-
ance with the provisions of the Statute and the Rules of Court.
(2) However. the Parties request the Court to order that the written
proceedings should consist of:
(LI) a Memorial presented by each of the Parties not later than ten
months after the date of notification of this Special Agreement to the
Registrar of the International Court of Justice;
(hi a Counter-Memorial presented by each of the Parties not later than
seven months after the date on which each has received the certified
copy of the Memorial of the other Party;
(ci a Reply presented by each of the Parties within such time-limits as the
Court may order.

(d) The Court may request additional written pleadings by the Parties if
it so determines.
(3) The above-mentioned parts of the written proceedings and their
annexes presented to the Registrar will not be transmitted to the other
Party until the Registrar has received the corresponding part of the pro-
ceedings from the said Party.

Article 4
(1) The Parties agree that, pending the final Judgment of the Court,
they will establish and implement a temporary water management régime
for the Danube.
(2) They further agree that, in the period before such a régimeis estab-
lished or implemented, if either Party believesits rights are endangered by
the conduct of the other, it may request immediate consultation and ref-
erence, if necessary, to experts, including the Commission of the European
Communities, with a view to protecting those rights; and that protection
shall not be sought through a request to the Court under Article 41 of the

Statute.

(3) This commitment is accepted by both Parties as fundamental to the
conclusion and continuing validity of the Special Agreement.
Article 5

(1) The Parties shall accept the Judgment of the Court as finaland bind-
ing upon them and shall execute it in its entirety and in good faith.
(2) Immediately after the transmission of the Judgment the Parties shall
enter into negotiations on the modalities for its execution.
(3) If they are unable to reach agreement within six months, either
Party may request the Court to render an additional Judgment to deter-
mine the modalities for executing its Judgment.
Article 6

(1) The present Special Agreement shall be subject to ratification. (2) The instruments of ratification shall be exchanged as soon as pos-
sible inBrussels.
(3) The present Special Agreement shall enter into force on the date of
exchange of instruments of ratification. Thereafter it willbe notifiedjointly
to the Registrar of the Court.
In witness whereof the undersigned being duly authorized thereto, have
signed the present Special Agreement and have affixed thereto their seals."

3. Pursuant to Article 40, paragraph 3, of the Statute and Article 42 of the
Rules of Court, copies of the notification and of the Special Agreement were
transmitted by the Registrar to the Secretary-General of the United Nations,
Members of the United Nations and other States entitled to appear before the
Court.
4. Since the Court included upon the Bench no judge of Slovak nationality,
Slovakia exercised its right under Article 31, paragraph 2, of the Statute to
choose a judge ad hoc to sit in the case: it chose Mr. Krzysztof Jan Skubi-
szewski.

5. By an Order dated 14July 1993,the Court fixed 2 May 1994as the time-
limit for the filing by each of the Parties of a Memorial and 5 December 1994
for the filing by each of the Parties of a Counter-Memorial. having regard to
the provisions of Article 3, paragraph 2 (a) and (b), of the Special Agreement.
Those pleadings were duly filed within the prescribed time-limits.

6. By an Order dated 20 December 1994, the President of the Court,
having heard the Agents of the Parties, fixed 20 June 1995 as the time-limit
for the filing of the Replies, having regard to the provisions of Article3, para-
graph 2 (c), of the Special Agreement. The Replies were duly filed within the
time-limit thus prescribed and, as the Court had not asked for the submission
of additional pleadings, the case was then ready for hearing.
7. By letters dated 27 January 1997,the Agent of Slovakia, referring to the
provisions of Article 56,paragraph 1,of the Rules of Court, expressed his Gov-
ernment's wish to produce two new documents; by a letter dated 10 February
1997, the Agent of Hungary declared that his Government objected to their
production. On 26 February 1997, after having duly ascertained the views of
the two Parties, the Court decided, in accordance with Article 56, paragraph 2,
of the Rules of Court, to authorize the production of those documents under

certain conditions of which the Parties were advised. Within the time-limit fixed
by the Court to that end, Hungary submitted comments on one of those docu-
ments under paragraph 3 of that same Article. The Court authorized Slovakia
to comment in turn upon those observations, as it had expressed a wish to do
so; its comments were received within the time-limit prescribed for that pur-
pose.
8. Moreover, each of the Parties asked to be allowed to show a video cas-
sette in the course of the oral proceedings. The Court agreed to those requests,
provided that the cassettes in question were exchanged in advance between the
Parties, through the intermediary of the Registry. That exchange was effected
accordingly.
9. In accordance with Article 53, paragraph 2, of the Rules of Court. the
Court decided, after having ascertained the views of the Parties. that copies of
the pleadings and documents annexed would be made available to the public as
from the opening of the oral proceedings.
10. By a letter dated 16June 1995,the Agent of Slovakia invited the Court14 GAB~IKOVO-NAGYMAROS PROJECT (JUDGMENT)

to visit the locality to which the case relates and there to exercise its functions
with regard to the obtaining of evidence, in accordance with Article 66 of the
Rules of Court. For his part, the Agent of Hungary indicated, by a letter dated
28 June 1995,that, if the Court should decide that a visit of that kind would be
useful, his Government would be pleased to co-operate in organizing it. By a
letter dated 14November 1995,the Agents of the Parties jointly notified to the
Court the text of a Protocol of Agreement, concluded in Budapest and New
York the same day, with a view to proposing to the Court the arrangements
that might be made for such a visitinsitu; and, by a letter dated 3 February
1997,they jointly notified to it the text of Agreed Minutes drawn up in Buda-
pest and New York the same day, which supplemented the Protocol of Agree-
ment of 14 November 1995. By an Order dated 5 February 1997, the Court

decided to accept the invitation to exercise its functions with regard to the
obtaining of evidence at a place to which the case relates and, to that end, to
adopt the arrangements proposed by the Parties. The Court visited the area
from 1to 4 April 1997; it visited a number of locations along the Danube and
took note of the technical explanations given by the representatives who had
been designated for the purpose by the Parties.
Il. The Court held a first round of ten public hearings from 3 to 7 March
and from 24 to 27 March 1997,and a second round of four public hearings on
10, 11, 14 and 15 April 1997,after having made the visit in situ referred to in
the previous paragraph. During those hearings, the Court heard the oral argu-
ments and replies of:

For Hungary: H.E. Mr. Szénasi,
Professor Valki,
Professor Kiss,
Professor Vida,
Professor Carbiener,
Professor Crawford,
Professor Nagy,
Dr. Kern,
Professor Wheater,

Ms Gorove.
Professor Dupuy,
Professor Sands.
For Slovakia: H.E. Dr. Tomka,
Dr. Mikulka,
Mr. Wordsworth,
Professor McCaffrey,
Professor Mucha,

Professor Pellet,
Mr. Refsgaard,
Sir Arthur Watts.
12. The Parties replied orally and in writing to various questions put by
Members of the Court. Referring to the provisions of Article 72 of theRules of
Court, each of the Parties submitted to the Courtits comments upon the replies

given by the other Party to some of those questions.15 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

13. In the course of the written proceedings, the following submissions were
presented by the Parties:

On hekaif of Hungary,

in the Memorial, the Counter-Memorial and the Reply (mutatis mutandis iden-
ticai texts:

"On the basis of the evidence and legal argument presented in the
Memorial, Counter-Memorial and this Reply, the Republic of Hungary

Reyuests the Court to rrdjudgeand declare
First, that the Republic of Hungary was entitled to suspend and subse-
quently abandon the works on the Nagymaros Project and on the part of
the Gabtikovo Project for which the Treaty attributed responsibility to the
Republic of Hungary;
Second, that the Czech and Slovak Federal Republic was not entitled to
proceed to the 'provisional solution' (damming up of the Danube at river
kilometre 1851.7on Czechoslovak territory and resulting consequences on

water and navigation course);

Tizird, that by its Declaration of 19 May 1992, Hungary validly termi-
nated the Treaty on the Construction and Operation of the Gabtikovo-
Nagymaros Barrage System of 16 September 1977:

Rrqzre.~tsthe Court to adjzldgeand declarefurtller

that the legal consequences of these findings and of the evidence and the
arguments presented to the Court are as follows:

(1) that the Treaty of 16September 1977has never been in force between
the Republic of Hungary and the Slovak Republic;
(2) that the Slovak Republic bears responsibility to the Republic of Hun-
gary for maintaining in operationthe 'provisional solution' referred to
above ;
(3) that the Slovak Republic is internationally responsible for the damage
and loss suffered by the Republic of Hungary and by its nationals as a
result of the 'provisional solution';
(4) that the Slovak Republic is under an obligation to make reparation in
respect of such damage and loss, the amount of such reparation, if it
cannot be agreed by the Parties within six months of the date of the
Judgment of the Court,to be deterrnined by the Court;
(5) that the Slovak Republic is under the following obligations:

(a) to return the waters of the Danube to their course along the
international frontier between the Republic of Hungary and the
Slovak Republic, that is to Say the main navigable channel as
defined by applicable treaties;
(b) to restore the Danube to the situation it was in prior to the
putting into effect of the provisional solution: and
(c) to provide appropriate guarantees against the repetition of the
damage and loss suffered by the Republic of Hungary and by its
nationals."16 GABCIKOVO-NAGYMAROSPROJECT(JUDGMENT)

On behaif of Slovakia,
in the Memorial, the Counter-Memorial and the Reply (mutatis mutandis iden-

tical texts:
"On the basis of the evidence and legal arguments presented in the Slo-
vak Memorial, Counter-Memorial and in this Reply, and reserving the
right to supplement or amend its claims in the light of further written
pleadings, the Slovak Republic

Requests fhe Court to udjudge and declare:
1. That the Treaty between Czechoslovakia and Hungary of 16September
1977 concerning the construction and operation of the Gabtikovol
Nagymaros Systemof Locks, and related instruments, and to which the
Slovak Republic is the acknowledged successor, is a treaty in force and
has been so from the date of its conclusion; and that the notification of
termination by the Republic of Hungary on 19 May 1992was without
legal effect.
2. That the Republic of Hungary was not entitled to suspend and subse-

quently abandon the works on the Nagymaros Project and on that part
of the Gabtikovo Project for which the 1977Treaty attributed respon-
sibility to the Republic of Hungary.
3. That the act of proceeding with and putting into operation Variant C,
the 'provisional solution', was lawful.
4. That the Republic of Hungary must therefore cease forthwith al1con-
duct which impedes the full and bona fide implementation of the 1977
Treaty and must take al1 necessary steps to fulfil its own obligations
under the Treaty without further delay in order to restore compliance
with the Treaty.
5. That, in consequence of its breaches of the 1977Treaty, the Republic of
Hungary is liable to pay, and the Slovak Republic is entitled to receive,
full compensation for the loss and damage caused to the Slovak Repub-
lic by those breaches, plus interest and loss of profits, in the amounts
to be determined by the Court in a subsequentphase of the proceedings

in this case."
14. In the oral proceedings. the following submissions were presented by the
Parties

On behaif of Huagury,
at the hearing of 11 April 1997:

The submissions read at the hearing were mutatis mutandis identical to those
presented by Hungary during the written proceedings.
On behalf of'Slovakia,

at the hearing of 15April 1997 :
"On the basis of the evidence and legal arguments presented in its writ-
ten and oral pleadings, the Slovak Republic,

Requests the Court to adjudge and declare:
1. That the Treaty, as defined in the first paragraph of the Preamble to the
Compromis between the Parties, dated 7 April 1993, concerning the
construction and operation of the GabtikovolNagymaros System of
Locks and related instruments, concluded between Hungary and Czechoslovakia and with regard to which the Slovak Republic is the
successor State, has never ceased to be in force and so remains, and
that the notification of 19 May 1992of purported termination of the
Treaty by the Republic of Hungary was without legal effect;
2. That the Republic of Hungary was not entitled to suspend and subse-
quently abandon theworks onthe Nagymaros Project and on that part
of the Gabeikovo Project for which the 1977Treaty attributes respon-
sibility to the Republic of Hungary;
3. That the Czech and Slovak Federal Republic was entitled,in Novem-
ber 1991,to proceed withthe 'provisionalsolution' and to put this sys-
tem into operation from October 1992;and that the Slovak Republic
was, and remains, entitled to continue the operation of this system;

4. That the Republic of Hungary shall therefore cease forthwith al1con-
duct which impedes the bona fide implementation of the 1977Treaty
and shall take al1necessarysteps to fulfilits own obligations under the

Treaty without further delay in order to restore compliance with the
Treaty, subject to any amendments which may be agreed between the
Parties;
5. That the Republic of Hungary shall giveappropriate guarantees that it
will not impede the performance of the Treaty, and the continued
operation of the system;
6. That, in consequenceof its breachesof the 1977Treaty, the Republicof
Hungary shall, in addition to immediately resumingperformance of its
Treaty obligations, pay to the Slovak Republic full compensation for
the lossand damage, including loss ofprofits, caused by those breaches
together with interest thereon;
7. That the Parties shall immediatelybegin negotiations with a view, in
particular, to adopting a new timetable and appropriate measures for
the implementation of the Treaty by both Parties, and to fixing the
amount of compensation due by the Republic of Hungary to the Slo-
vak Republic; and that. if the Parties are unable to reach an agreement
within six months, either one of them may request the Court to render
an additional Judgment to determine the modalities for executing its
Judgment."

15. The present case arose out ofthe signature, on 16 September 1977,
by the Hungarian People's Republic and the Czechoslovak People's
Republic, of a treaty "concerning the construction and operation of the
GabEikovo-Nagymaros System of Locks" (hereinafter called the "1977

Treatv"). The names of the two contractine States have varied over the
yearst hereinafter they will be referred touas Hungary and Czechoslo-
vakia. The 1977 Treaty entered into force on 30 June 1978.
It provides forthe construction and operation of a System of Locks by
the parties as a "joint investment". According to its Preamble, the bar-
rage system was designed to attain

"the broad utilization of the natural resources of the Bratislava-
Budapest section of the Danube river for the development of water GABC~KOVO-NAGYMAROSPROJECT (JUDGMENT)

resources, energy, transport, agriculture and other sectors of the
national economy of the Contracting Parties".

The joint investment was thus essentially aimed at the production of
hydroelectricity, the improvement of navigation on the relevant sec-
tion of the Danube and the protection of the areas along the banks
against flooding. At the same time, by the terms of the Treaty, the con-
tracting parties undertook to ensure that the quality of water in the Dan-
ube was not impaired as a result of the Project, and that compliance with

the obligations for the protection of nature arising in connection with the
construction and operation of the System of Locks would be observed.
16. The Danube is the second longest river in Europe, flowingalong or
across the borders of nine countries in its 2,860-kilometre course from the
Black Forest eastwards to the Black Sea. For 142kilometres, it formsthe
boundary between Slovakia and Hungary. The sector with which this
case is concerned is a stretch of approximately 200 kilometres, between
Bratislava in Slovakia and Budapest in Hungary. Below Bratislava, the
river gradient decreases markedly, creating an alluvial plain ofrave1and
sand sediment. This plain is delimited to the north-east, in Slovak terri-
tory, by the Maly Danube and to the south-west, in Hungarian territory,
by the Mosoni Danube. The boundary between the two States is consti-
tuted, in the major part of that region, by the main channel of the river.
The area lying between the Mali Danube and that channel, in Slovak
territory, constitutes theitni Ostrov; the area between the main chan-
ne1 and the Mosoni Danube, in Hungarian territory, constitutes the.
Szigetkoz. Cunovo and, further downstream, GabCikovo, are situated in
this sector of the river on Slovak territory, Cunovo on the right bank and
GabCikovo on the left. Further downstream, after the confluence of the
various branches, the river enters Hungarian territory and the topo-

graphy becomes hillier. Nagymaros lies in a narrow valleyat a bend in the
Danube just before it turns south, enclosing the large river island of Szen-
tendre before reaching Budapest (see sketch-map No. 1, p. 19below).

17. The Danube has always played a vital part in the commercial and
economic development of its riparian States, and has underlined and
reinforced their interdependence, making international CO-operation
essential. Improvements to the navigation channel have enabled the Dan-
ube, now linked by canal to the Main and thence to the Rhine, to become
an important navigational artery connecting the North Sea to the Black
Sea. In the stretch of river to which the case relates, flood protection
measures have been constructed over the centuries, farming and forestry
practised, and, more recently, there has been an increase in population
and industrial activity in therea. The cumulative effects on the river and
on the environment of various human activities over the years have not
al1been favourable, particularly for the water régime.20 GABCIKOVO-NAGYM PAORJCT (JUDGMENT)

Only by international CO-operation could action be taken to alleviate
these problems. Water management projects along the Danube have fre-
quently sought to combine navigational improvements and flood protec-
tion with the production of electricity through hydroelectric power plants.
The potential of the Danube for the production of hydroelectric power
has been extensively exploited by some riparian States. The history of
attempts to harness the potential of the particular stretch of the river at
issue inthese proceedings extends over a 25-year period culminating in
the signature of the 1977Treaty.

18. Article1, paragraph 1, of the 1977Treaty describes the principal
works to be constructed in pursuance of the Project. It provided for the
building of two series of locks, one at Gabëikovo (in Czechoslovak ter-

ritory) and the other at Nagymaros (in Hungarian territory), to consti-
tute "a single and indivisible operational system of works" (see sketch-
map No. 2, p. 21 below). The Court will subsequently have occasion to
revert in more detail to those works, which were to comprise,interalia, a
reservoir upstream of Dunakiliti, in Hungarian and Czechoslovak terri-
tory; a dam at Dunakiliti, in Hungarian territory; a bypass canal, in
Czechoslovak territory, on which was to be constructed the Gabcikovo
System of Locks (together with a hydroelectric power plant with an
installed capacity of 720 megawatts (MW)); the deepening of the bed of
the Danube downstream of the place at which the bypass canal was to
rejoin the old bed of the river; a reinforcement of flood-control works
along the Danube upstream of Nagymaros; the Nagymaros System of
Locks, in Hungarian territory (with a hydroelectric power plant of a
capacity of 158MW); and the deepening of the bed of the Danube down-

Stream.
Article 1, paragraph 4, of the Treaty further provided that the techni-
cal specifications concerning the system would be included in the "Joint
Contractual Plan" which was to be drawn up in accordance with the
Agreement signed by the two Governments for this purpose on 6 May
1976;Article 4, paragraph 1, for its part, specifiedthat "the joint invest-
ment [would] be carried out in conformity with the joint contractual
plan".
According to Article 3, paragraph 1 :

"Operations connected with the realization of the joint investment
and with the performance of tasks relating to the operation of the
System of Locks shall be directed and supervised by the Govern-
ments of the Contracting Parties through . . .(. . .'government
delegates')."

Those delegates had, interalia, "to ensure that construction of the Sys-
tem of Locks is . . .carried out in accordance with the approved joint
contractual plan and the project work schedule". When the works were
brought into operation, they were moreover "To establish the operating Bratislava

Slovakia

/

\

Komarom

Szentendre
Island

SKETCH-MAPNO.2 Hungary
The OriginalProject

N.B.: This sketch-maphas
beenpreparedfor illustrative
purposesonly

Sketch-mapnotoscale II and operational procedures of the System of Locks and ensure compli-
ance therewith."
Article 4, paragraph 4, stipulated that:
"Operations relating to the joint investment [should] be organized
by the Contracting Parties in such a way that the power generation
plants [would] be put into service during the period 1986-1990."

Article 5 provided that the cost of the joint investment would be borne
by the contracting parties in equal measure. It specified the work to be
carried out by each one of them. Article 8 further stipulated that the
Dunakiliti dam, the bypass canal and the two series of locks at Gab-
Cikovo and Nagymaros would be "jointly owned" by the contracting
parties "in equal measure". Ownership of the other works was to be
vested in the State on whose territory they were constructed.
The parties were likewiseto participate in equal measure in the use of
the system put in place, and more particularly in the use of the base-load
and peak-load power generated at ,the hydroelectric power plants
(Art. 9).

According to Article 10,the works were to be managed by the State on
whose territory they were located, "in accordance with the jointly-agreed
operating and operational procedures", while Article 12 stipulated that
the operation, maintenance (repair) and reconstruction costs of jointly
-owned works of the System of Locks were also to be borne jointly by the
contracting parties in equal measure.

According to Article 14,
"The discharge specified in the water balance of the approved
joint contractual plan shall be ensured in the bed of the Danube
[between Dunakiliti and Sap] unless natural conditions or other cir-

cumstances temporarily require a greater or smaller discharge."

Paragraph 3 of that Article was worded as follows:

"In the event that the withdrawal of water in the Hungarian-
Czechoslovak section of the Danube exceeds the quantities of water
specified in the water balance of the approved joint contractual plan
and the excess withdrawal results in a decrease in the output of
electric power, the share of electric power of the Contracting Party
benefiting from the excess withdrawal shall be correspondingly
reduced."
Article 15specified that the contracting parties

"shall ensure, by the means specified in the joint contractual plan,
that the quality of the water in the Danube is not impaired as a
result of the construction and operation of the System of Locks". Article 16 set forth the obligations of the contracting parties concern-
ing the maintenance of the bed of the Danube.
Article 18, paragraph 1, provided as follows :
"The Contracting Parties, in conformity with the obligations pre-

viously assumed by them, and in particular with article 3 of the Con-
vention concerning the regime of navigation on the Danube, signed
at Belgrade on 18August 1948, shall ensure uninterrupted and safe
navigation on the international fairway both during the construction
and during the operation of the System of Locks."

It was stipulated in Article 19 that:

"The Contracting Parties shall, through the means specifiedin the
joint contractual plan, ensure compliance with the obligations for
the protection of nature arising in connection with the construction
and operation of the System of Locks."

Article 20 provided for the contracting parties to take appropriate
measures, within the framework of their national investments, for the
protection of fishing interests in conformity with the Convention con-
cerning Fishing in the Waters of the Danube, signed at Bucharest on
29 January 1958.
According to Article 22, paragraph 1, of the Treaty, the contracting
parties had, in connection with the construction and operation of the
System of Locks, agreed on minor revision to the course of the State
frontier between them as follows:

"(d) In the Dunakiliti-HruSov head-water area, the State frontier
shall run from boundary point 161.V.O.A.to boundary stone
No. 1.5. in a straight line in such a way that the territories
affected, to the extent of about 10-10hectares shall be offset
between the two States."
It was further provided, in paragraph 2, that the revision of the State

frontier and the exchange of territories so provided for should be effected
"by the Contracting Parties on the basis of a separate treaty". No such
treaty was concluded.
Finally a dispute settlement provision was contained in Article 27,
worded as follows:
"1. The settlement of disputes in matters relating to the realiza-
tion and operation of the System of Locks shall be a function of the
government delegates.

2. If the government delegates are unable to reach agreement on
the matters in dispute, they shall refer them to the Governments of
the Contracting Parties for decision."
19. The Joint Contractual Plan, referred to in the previous paragraph,
set forth, on a large number of points, both the objectives of the systemand the characteristics of the works. In its latest version it specified in
paragraph 6.2 that the GabCikovo bypass canal would have a discharge
capacity of 4,000 cubic metres per second (m3/s).The power plant would
include "Eight . . .turbines with 9.20 m diameter running wheels" and
would "mainly operate in peak-load time and continuously during high
water". This type of operation would give an energy production of
2,650 gigawattihours (GWh) per annum. The Plan further stipulated in
paragraph 4.4.2 :
"The low waters are stored every day, which ensures the peak-

load time operation of the GabEikovo hydropower plant ... a mini-
mum of 50 m3/sadditional water is provided for the old bed [of the
Danube] besides the water supply of the branch system."
The Plan further specifiedthat, in the event that the discharge into the
bypass canal exceeded 4,000-4,500 m3/s, the excess amounts of water
would be channelled into the old bed. Lastly, according to paragraph 7.7
of the Plan:

"The common operational regulation stipulatesthat concerning the
operation of the Dunakiliti barrage in the event of needduring the
growing season 200m3/sdischarge mustbe releasedinto the old Dan-
ube bed, in addition to the occasionalpossibilitiesfor rinsingthe bed."

The Joint Contractual Plan alsocontained "Preliminary Operating and
Maintenance Rules", Article 23 of which specified that "The final oper-
ating rules [should] be approved within a year of the setting into opera-
tion of the system." (Joint Contractual Plan, Summary Documentation,
Vol. 0-1-A.)
Nagymaros, with six turbines, was, according to paragraph 6.3 of
the Plan, to be a "hydropower station . . type of a basic power-station
capable of operating in peak-load time for five hours at the discharge
interval between 1,000-2,500m3/s"per day. The intended annual produc-
tion was to be 1,025GWh (Le.,38per cent of the production of GabEikovo,
for an installed power only equal to 21 per cent of that of GabCikovo).

20. Thus, the Project was to have taken the form of an integrated joint
project with the two contracting parties on an equal footing in respect of
the financing, construction and operation of the works. Its single and
indivisible nature was to have been realized through the Joint Contrac-
tua1Plan which complemented the Treaty. In particular, Hungary would
have had control of the sluices at Dunakiliti and the works at Nagy-
maros, whereas Czechoslovakia would have had control of the works at
GabCikovo.

21. The schedule of work had for its part been fixed inan Agreement
on mutual assistance signed by the two parties on 16 September 1977,at25 GABCIKOVO-NAGYM RROJCT (JUDGMENT)

the same time as the Treaty itself. The Agreement moreover made some
adjustments to the allocation of the works between the parties as laid

down by the Treaty.
Work on the Project started in 1978.On Hungary's initiative, the two
parties first agreed, by two Protocols signed on 10 October 1983 (one
amending Article 4,paragraph 4,of the 1977 Treaty and the other the
Agreement on mutual assistance), to slow the work down and to post-
pone putting into operation the power plants, and then, by a Protocol

signed on 6 February 1989 (which amended the Agreement on mutual
assistance), to accelerate the Project.
22. As a result of intense criticism which the Project had generated in
Hungary, the Hungarian Government decided on 13 May 1989 to sus-
pend the works at Nagymaros pending the completion of various studies

which the competent authorities were to finish before 31 July 1989. On
21 July 1989,the Hungarian Government extended the suspension of the
works at Nagymaros until 31 October 1989,and, in addition, suspended
the works at Dunakiliti until theame date. Lastly, on 27 October 1989,
Hungary decided to abandon the works at Nagymaros and to maintain
the status quo at Dunakiliti.

23. During this period, negotiations were being held between the
parties. Czechoslovakia also started investigating alternative solutions.
One of them, subsequently known as "Variant CM,entailed a unilateral
diversion of the Danube by Czechoslovakia on its territory some 10kilo-
metres upstream of Dunakiliti (see sketch-map Nol 3, p. 26 below). In its

final stage, Variant C included the construction at Cunovo of an overflow
dam and a levee linking that dam to the south bank of the bypass canal.
The corresponding reservoir was to have a smaller surface area andro-
vide approximately 30 per cent less storage than the reservoir initially
contemplated. Provision was made for ancillary works, namely: an intake
structure to supply the Mosoni Danube; a weir to enable, interdia,

floodwater to be directed along the old bed of the Danube: an auxiliary
shiplock; and two hydroelectric power plants (one capable of an aniiual
production of 4 GWh on the Mosoni Danube, and the other with a pro-
duction of 174GWh on the old bed of the Danube). The supply of water
to the side-arms of the Danube on the Czechoslovak bank was to be

secured by means of two intake structures in the bypass canal at
DobrohoSt' and GabEikovo. A solution was to be found for the Hungar-
ian bank. Moreover, the question of the deepening of the bed of the Dan-
ube at the confluence of the bypass canal and the old bed of the river
remained outstanding.

On 23 July 1991, the Slovak Government decided "to begin, in Sep-
tember 1991, construction to put the GabEikovo Project into operation
by the provisional solution". That decision was endorsed by the Federal
Czechoslovak Government on 25 July. Work on Variant C began
in November 1991. Discussions continued between the two parties but to

no avail, and, on 19 May 1992, the Hungarian Government transmitted27 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

to the Czechoslovak Government a Note Verbale terminating the 1977
Treaty with effect from 25 May 1992. On 15 October 1992, Czechoslo-
vakia began work to enable the Danube to be closed and, starting on
23 October, proceeded to the damming of the river.

24. On 23 October 1992, the Court was seised of an "Application of

the Republic of Hungary v. The Czech and Slovak Federal Republic on
the Diversion of the Danube River"; however, Hungary acknowledged
that there was no basis on which the Court could have founded its juris-
diction to entertain that application, on which Czechoslovakia took no
action. In the meanwhile, the Commission of the European Communities
had offered to mediate and, during a meeting of the two parties with the

Commission held in London on 28 October 1992,the parties entered into
a series of interim undertakings. They principally agreed that the dispute
would be submitted to the International Court of Justice, that a tripartite
fact-finding mission should report on Variant C not later than 31 Octo-
ber, and that a tripartite group of independent experts would submit sug-
gestions as to emergency measures to be taken.

25. On 1 January 1993 Slovakia became an independent State. On
7 April 1993, the "Special Agreement for Submission to the International
Court of Justice of the Differences between the Republic of Hungary and
the Slovak Republic concerning the GabEikovo-Nagymaros Project" was
signed in Brussels, the text of whichs reproduced in paragraph 2 above.
After the SpecialAgreement was notified to the Court, Hungary informed
the Court, by a letter dated 9 August 1993, that it considered its "initial

Application [to bel now without object, and . . . lapsed".
According to Article 4 of the Special Agreement, "The Parties [agreed]
that, pending the final Judgment of the Court, they [would]establish and
implement a temporary water management régime for the Danube."
However, this régime could not easily be settled. The filling of the
~unovo dam had rapidly led to a major reduction in the flow and in the

level of the downstream waters in the old bed of the Danubeas well as in
the side-arms of the river. On 26 August 1993, Hungary and Slovakia
reached agreement on the setting up of a tripartite group of experts (one
expert designated by each party and three independent experts designated
by the Commission of the European Communities)

"In order to provide reliable and undisputed data on the most
important effects of the current water discharge and the remedial
measures already undertaken as well as to make recommendations
for appropriate measures."

On 1 December 1993, the experts designated by the Commission of the
European Communities recommended the adoption of various measures
to remedy the situation on a temporary basis. The Parties were unable to

agree on these recommendations. After lengthy negotiations, they finally
concluded an Agreement "concerning CertainTemporary Technical Meas-
ures and Discharges in the Danube and Mosoni branch of the Danube",28 GABCIKOVO-NAGYM PAOJOCT (JUDGMENT)

on 19April 1995.That Agreement raised the discharge of water into the
Mosoni Danube to 43 m3/s.It provided for an annual average of 400 m3/s
in the old bed (not including flood waters). Lastly,it provided forthe con-
struction by Hungary of a partially underwater weir near to Dunakiliti
with a viewto improving the water supply to the side-arms of the Danube

on the Hungarian side. It was specified that this temporary agreement
would come to an end 14days after the Judgment of the Court.

26. The first subparagraph of the Preamble to the Special Agreement
covers the disputes arising between Czechoslovakia and Hungary con-
cerning the application and termination, not only of the 1977Treaty, but
also of "related instruments"; the subparagraph specifies that, for the
purposes of the Special Agreement, the 1977Treaty and the said instru-

ments shall be referred to as "the Treaty". "The Treaty" is expressly
referred to in the wording of the questions submitted to the Court in
Article 2, paragraph 1, subparagraphs (a) and (ci, of the Special
Agreement.
The Special Agreement however does not definethe concept of "related
instruments", nor does it list them. As for the Parties, they gave some
consideration to that question- essentially in the written proceedin-s
without reaching agreement as to the exact meaning of the expression or
as to the actual instruments referred to. The Court notes however that
the Parties seemed to agree to consider that that expression covers at

least the instruments linked to the 1977Treaty which implement it, such
as the Agreement on mutual assistance of 16 September 1977 and its
amending Protocols dated, respectively, 10October 1983and 6 February
1989 (see paragraph 21 above), and the Agreement as to the common
operational regulations of Plenipotentiariesulfillingduties related to the
construction and operation of the Gabtikovo-Nagymaros Barrage Sys-
tem signed in Bratislava on 11October 1979.The Court notes that Hun-
gary, unlike Slovakia, declined to apply the description of related instru-
ments to the 1977Treaty to theJoint Contractual Plan (see paragraph 19
above), which it refused to see as "an agreement at the same level as the
other . . related Treaties and inter-State agreements".

Lastly the Court notes that the Parties, in setting out the replies which ,
should in their view be given to the questions put in the Special Agree-
ment, concentrated their reasoning on the 1977 Treaty; and that they
would appear to have extended their arguments to "related instruments"
in considering them as accessories to a whole treaty system, whose fate
was in principle linked to that of the main part, the 1977 Treaty. The
Court takes note of the positions of the Parties and considers that its
not need to go into this matter further at this juncture.29 GABCIKOVO-NAGYM ARROEST (JUDGMENT)

27. The Court will now turn to a consideration of the questions
submitted by the Parties. In terms of Article 2, paragraph 1 (a), of the
Special Agreement, the Court is requested to decide first

"whether the Republic of Hungary was entitled to suspend and sub-
sequently abandon, in 1989, the works on the Nagymaros Project
and on the part of the GabCikovo Project for which the Treaty
attributed responsibility to the Republic of Hungary".

28. The Court would recall that the Gabrikovo-Nagymaros System of
Locks is characterized in Article 1, paragraph1, of the 1977Treaty as a
"single and indivisible operational system of works".
The principal works which were to constitute this system have been

described in general terms above (see paragraph 18). Details of them are
given in paragraphs 2 and 3 of Article 1 of the Treaty.
For GabMkovo, paragraph 2 lists the following works:

"(a) the Dunakiliti-HruSov head-water installations in the Danube
sector atr.km. (river kilometre(s)) 1860-1842, designed for a
maximum flood stage of 131.10 m.B. (metres above sea-level.
Baltic system), in Hungarian and Czechoslovak territory;

(6) the Dunakiliti dam and auxiliary navigation lock at r.km.

1842, in Hungarian territory ;
(c) the by-pass canal (head-water canal and tail-water canal) at
r.km. 1842-181 1,in Czechoslovak territory ;
(rl) series of locks on the by-pass canal, in Czechoslovak territory,
consisting of a hydroelectric power plant with installed capa-
city of 720MW, double navigation locks and appurtenances

thereto;
(el improved old bed of the Danube at r.km. 1842-1811, in the
joint Hungarian-Czechoslovak section;
(f) deepened and regulated bed of the Danube at r.km. 1811-
1791, in the joint Hungarian-Czechoslovak section."

For Nagymaros, paragraph 3specifies the following works:
"(a) head-water installations and flood-control works in the

Danube sector at r.km. 1791-1696.25 and in the sectors of
tributaries affected by flood waters, designed for a maximum
flood stage of 107.83 m.B., in Hungarian and Czechoslovak
territory;

(6) series of locks at r.km. 1696.25, in Hungarian territory, con-
sisting of a dam, a hydroelectric power plant with installed
capacity of 158 MW, double navigation locks and appur-
tenances thereto;
(ci deepened and regulated bed of the Danube, in both its
branches, at r.km. 1696.25-1657, in the Hungarian section."30 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

29. Moreover, the precise breakdown of the works incumbent on each
party was set out in Article 5, paragraph 5, of the 1977 Treaty, as fol-
lows:

"5. The labour and supplies required for the realization of the
joint investment shall be apportioned between the Contracting
Parties in the following manner:

(a) The Czechoslovak Party shall be responsible for:
(1) the Dunakiliti-HruSov head-water installations on the left
bank, in Czechoslovak territory ;
(2) the head-water canal of the by-pass canal, in Czecho-
slovak territory ;
(3) the GabCikovo series of locks, in Czechoslovak territory ;
(4) the flood-control works of the Nagymaros head-water
installations, in Czechoslovak territory, with the exception
of the lower Ipel district;

(5) restoration of vegetation in Czechoslovak territory;

(b) The Hungarian Party shall be responsible for

(1) the Dunakiliti-HruSov head-water installations on the
right bank, in Czechoslovak territory, including the con-
necting weir and the diversionary weir;
(2) the Dunakiliti-HruSov head-water installations on the
right bank, in Hungarian territory ;
(3) the Dunakiliti dam, in Hungarian territory;
(4) the tail-water canal of the by-pass canal, in Czechoslovak
territory;
(5) deepening of the bed of the Danube below Palkovicovo,
in Hungarian and Czechoslovak territory ;
(6) improvement of the old bed of the Danube, in Hungarian
and Czechoslovak territory ;

(7) operational equipment of the GabCikovo system of locks
(transportequipment, maintenance machinery), in Czecho-
slovak territory ;
(8) the flood-control works of the Nagymaros head-water
installations in the lower Ipel district, in Czechoslovak
territory;
(9) the flood-control works of the Nagymaros head-water
installations, in Hungarian territory;
(10) the Nagymaros series of locks, in Hungarian territory;
(11) deepening of the tail-water bed below the Nagymaros
system of locks, in Hungarian territory;
(12) operational equipment of the Nagymaros system of locks
(transport equipment, maintenance machinery), in Hun-
garian territory;

(13) restoration of vegetation in Hungarian territory."31 GABCIKOVO-NAGYM AROJEST (JUDGMENT)

30. As the Court has already indicated (see paragraph 18 above), Ar-
ticle 1, paragraph4, of the 1977 Treaty stipulated in general terms that
the "technical specifications" concerning the System of Locks would be

included in the "ioint contractual dan". The schedule of work had for its
part been fixed in an Agreement on mutual assistance signed by the two
parties on 16 September 1977 (see paragraph 21 above). In accordance
with the provisions of Article 1, paragraph 1, of that Agreement, the
whole of the works of the barr.+, svstem were to have been comoleted in
1991. As indicated in paragraph 2 of that same article, a summary con-

struction schedule was appended to the Agreement, and provision was
made for a more detailed schedule to be worked out in the Joint Con-
tractual Plan. The Agreement of 16 September 1977 was twice amended
further. By a Protocol signed on 10October 1983,the parties agreed first
to postpone the works and the putting into operation of the power plants
for four more years; then, by a Protocol signed on6 February 1989, the

parties decided, conversely, to bring them forward by 15 months, the
whole system having to be operational in 1994. A new summary con-
struction schedule was appended to each of those Protocols; those sched-
ules were in turn to be implemented by means of new detailed schedules,
included in the Joint ContractualPlan.

31. In spring 1989, the work on the GabCikovo sector was well
advanced: the Dunakiliti dam was 90 per cent complete, the Gabëikovo
dam was 85 per cent complete, and the bypass canal was between 60 per
cent complete (downstream of Gabcikovo) and 95 per cent complete
(upstream of GabCikovo) and the dykes of the Dunakiliti-HruSov reser-

voir were between 70 and 98 per cent complete, depending on the loca-
tion. This was not the case in the Nagymaros sector where, although
dykes had been built, the only structure relating to the dam itself was the
coffer-dam which was to facilitate its construction.
32. In the wake of the profound political and economic changes which
occurred at this time in central Europe, the Gabcikovo-Nagymaros

Project was the object, in Czechoslovakia and more particularly in Hun-
gary, of increasing apprehension, both within a section of public opinion
and in some scientific circles. The uncertainties not only about the eco-
nomic viability of the Project, but also, and more so, as to the guarantees
it offered for preservation of the environment, engendered a climate of
growing concern and opposition with regard to the Project.

33. It was against this background that, on 13May 1989,the Govern-
ment of Hungary adopted a resolution to suspend works at Nagymaros,
and ordered

"the Ministers concerned to commission further studies inorder to

place the Council of Ministers in a position where it can make well-
founded suggestions to the Parliament in connection with the amend-
ment of the international treaty on tinvestment. In the interests of32 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

the above, we must examine the international and legal conse-
quences, the technical considerations, the obligations related to con-
tinuous navigation on the Danube and the environmental/ecological
and seismic impacts of the eventual stopping of the Nagymaros
investment. To be further examined are the opportunities for the
replacement of the lost electric energy and the procedures for mini-
mising claims for compensation."

The suspension of the works at Nagymaros was intended to last for the
duration of these studies, which were to be completed by 31 July 1989.
Czechoslovakia immediately protested and a document defining the posi-
tion of Czechoslovakia was transmitted to the Ambassador of Hungary
in Prague on 15May 1989.The Prime Ministers of the two countries met
on 24 May 1989,but their talks did not lead to any tangible result. On
2 June, the Hungarian Parliament authorized the Government to begin
negotiations with Czechoslovakia for the purpose of modifying the 1977
Treaty.
34. At a meeting held by the Plenipotentiaries on 8 and 9 June 1989,
Hungary gave Czechoslovakia a number of assurances concerning the
continuation of works in the GabCikovo sector, and the signed Protocol
which records that meeting contains the following passage:

"The Hungarian Government Commissioner and the Hungarian
Plenipotentiary stated, that the Hungarian side will complete con-
struction of theGabCikovo Project in the agreed time and in accord-
ance with the project plans. Directives have already been given to
continue works suspended in the area due to misunderstanding."

These assurances were reiterated in a letter that the Commissioner of the
Government of Hungary addressed to the Czechoslovak Plenipotentiary
on 9 June 1989.
3.5. With regard to the suspension of work at Nagymaros, the Hungar-
ian Deputy Prime Minister, in a letter dated 24June 1989addressed to his
Czechoslovak counterpart, expressed himselfin the following terms:

"The Hungarian Academy of Sciences(HAS)has studied the envi-
ronmental, ecological and water quality as well as the seismological
impacts of abandoning or implementing the Nagymaros Barrage of
theGabCikovo-Nagymaros Barrage System (GNBS).

.............................
Having studied the expected impacts of the construction in accord-
ance with the original plan, the Committee [ad hoc] of the Academy
[set up for this purpose] came to the conclusion that we do not have
adequate knowledge of the consequences of environmental risks.

In its opinion, the risk of constructing the Barrage System in
accordance with the original plan cannot be considered acceptable.
Of course, it cannot be stated either that the adverse impacts will33 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

ensue for certain, therefore, according to their recommendation,
further thorough and time consuming studies are necessary."

36. The Hungarian and Czechoslovak Prime Ministers met again on
20 July 1989 to no avail. lmmediately after that meeting, the Hungarian
Government adopted a second resolution, under which the suspension of
work at Nagymaros was extended to 31 October 1989. However, this
resolution went further, as it also prescribed the suspension, until the

same date, of the "Preparatory works on the closure of the riverbed at
. . . Dunakiliti"; the purpose of this measurewas to invite "international
scientific institutions [and] foreign scientific institutes and experts" to co-
operate with "the Hungarian and Czechoslovak institutes and experts"
with a view to an assessment of the ecological impact of the Project and
the "development of a technical and operational water quality guarantee
system and . . . its implementation".

37. In the ensuing period, negotiations were conducted at various levels
between the two States, but proved fruitless. Finally, by a letter dated
4 October 1989, the Hungarian Prime Minister formally proposed to
Czechoslovakia that the Nagymaros sector of the Project be abandoned
and that an agreement be concluded with a view to reducing the ecologi-
cal risks associated with the Gabëikovo sector of the Project. He pro-

posed that that agreement should be concluded before 30 July 1990.
The two Heads of Government met on 26 October 1989, and were
unable to reach agreement. By a Note Verbale dated 30 October 1989,
Czechoslovakia, confirming the views it had expressed during those talks,
proposed to Hungary that they should negotiate an agreement on a sys-
tem of technical, operational and ecological guarantees relating to the

Gabëikovo-Nagymaros Project, "on the assumption that the Hungarian
party will immediatelycommence preparatory work on the refilling of the
Danube's bed in the region of Dunakiliti". It added that the technical
principles of the agreement could be initialled within two weeks and that
the agreement itself ought to be signed before the end of March 1990.
After the principles had been initialled, Hungary "[was to] start the actual

closure of the Danube bed". Czechoslovakia further stated its willingness
to "conclu[de] . . . a separate agreement in which both parties would
oblige themselves to limitations or exclusion of peak hour operation
mode of the . . . System". It also proposed "to return to deadlines indi-
cated in the Protocol of October 1983", the Nagymaros construction
deadlines being thus extended by 15months, so as to enable Hungary to

take advantage of the time thus gained to study the ecological issues and
formulate its own proposais in due time. Czechoslovakia concluded by
announcing that, should Hungary continue unilaterally to breach the
Treaty, Czechoslovakia would proceed with a provisional solution.

In the meantime, the Hungarian Government had on 27 October
adopted a further resolution, deciding to abandon the construction of theNagymaros dam and to leave in place the measures previously adopted
for suspending the works at Dunakiliti. Then, by Notes Verbales dated
3 and 30 November 1989,Hungary proposed to Czechoslovakia a draft
treaty incorporating itsearlier proposals, relinquishing peak power opera-
tion of the Gabëikovo power plant and abandoning the construction of

the Nagymaros dam. The draft provided for the conclusion of an agree-
ment on the completion of Gabëikovo in exchange for guarantees on
protection of the environment. It finally envisaged the possibility of one
or other party seising an arbitral tribunal or the International Court of
Justice in the event that differences of view arose and persisted between
the two Governments about the construction and operation of the Gab-
Cikovodam, as well as measures to be taken to protect the environment.
Hungary stated that it was ready to proceed immediately "with the pre-
paratory operations for the Dunakiliti bed-decanting", but specifiedthat
the river would not be dammed at Dunakiliti until the agreement on
guarantees had been concluded.
38. During winter 1989-1990,the political situation in Czechoslovakia
and Hungary alike was transformed, and the new Governments were
confronted with many new problems.
In spring 1990. the new Hungarian Government, in presenting its
National Renewal Programme, announced that the whole of the Gab-

ëikovo-Nagymaros Project was a "mistake" and that it would initiate
negotiations as soon as possible with the Czechoslovak Government "on
remedying and sharing the damages". On 20 December 1990,the Hun-
garian Government adopted a resolution for the opening of negotiations
with Czechoslovakia on the termination of the Treatv b, , mutual consent
and the conclusion of an agreement addressing the consequences of the
termination. On 15February 1991,the Hungarian Plenipotentiary trans-
mitted a draft agreement along those lines to his Czechoslovak counter-
part.
On the same day, the Czechoslovak President declared that the Gab-
Cikovo-Nagymaros Project constituted a "totalitarian, gigomaniac monu-
ment which is against nature", while emphasizing that "the problem [was]
that [theGabëikovo power plant] [had]already been built". For his part,
the Czechoslovak Minister of the Environment stated, in a speech given
to Hungarian parliamentary committees on 11September 1991,that "the
G/N Project [was]an old, obsolete one", but that, if there were "many

reasons to change, modify the treaty . . it [was]not acceptable to cancel
the treaty .. .and negotiate later on".
During the ensuing period, Hungary refrained from completing the
work for which it was still responsible at Dunakiliti. Yet it continued to
maintain the structures it had already built and,at the end of 1991,com-
pleted the works relating to the tailrace canal of the bypass canal assigned
to it under Article 5, paragraph 5 (b), of the 1977Treaty.35 GABCIKOVO-NAGYMAROSPROJECT (JUDGMENT)

39. The two Parties to this case concur in recognizing that the 1977
Treaty, the above-mentioned Agreement on mutual assistance of 1977
and the Protocol of 1989were validly concluded and were duly in force
when the facts recounted above took place.

Further, they do not dispute the fact that, however flexible they may
have been, these texts did not envisage the possibility of the signatories
unilaterally suspending or abandoning the work provided for therein, or
even carryingit out according to a new schedule not approved by the two
partners.
40. Throughout the proceedings, Hungary contended that, although it
did suspend or abandon certain works, on the contrary, it never sus-
pended the application of the 1977Treaty itself. To justify its conduct, it
reliedessentially on a "state of ecological necessity".

Hungary contended that the various installations in the GabEikovo-
Nagymaros System of Locks had been designed to enable the Gabtikovo

power plant to operate in peak mode. Water would only have come
through the plant twiceeach day, at times of peak power demand. Opera-
tion in peak mode required the vast expanse (60 km') of the planned
reservoir at Dunakiliti, as well as the Nagymaros dam, which was to
alleviate the tidal effectsand reduce the variation in the water levelwn-
Streamof Gabtikovo. Such a system, considered to be more economically
profitable than using run-of-the-river plants, carried ecological risks
which it found unacceptable.

According to Hungary, the principal ecological dangers which would
have been caused by this system were as follows. At GabMkovoi
Dunakiliti, under the original Project, as specified in the Joint Contrac-

tua1 Plan, the residual discharge into the old bed of the Danube was
limited to 50m3/s,in addition to the water provided to the system of side-
arms. That volume could be increased to 200 m3/s during the growing
season. Additional discharges, and in particular a number of artificial
floods, could also be effected, at an unspecified rate. In these circum-
stances, the groundwater levelwould have fallen in most of the Szigetkoz.
Furthermore, the groundwater would then no longer have been supplied
by the Danube - which, on the contrary, would have acted as a drain -
but by the reservoir of stagnant water at Dunakiliti and the side-arms
which would have become silted up. In the long term, the quality of water
would have been seriously impaired. As for the surface water, risks of
eutrophication would have arisen, particularly in the reservoir; instead of
the old Danube there would have been a river choked with sand, where

only a relative trickle of water would have flowed.The network of arms
would have been for the most part cut off from the principal bed. The
fluvial fauna and flora, likethose in the alluvial plains, would have been
condemned to extinction.
As for Nagymaros, Hungary argued that, if that dam had been built,the bed of the Danube upstream would have silted up and, consequently,
the quality of the water collected in the bank-filtered wells would have
deteriorated in this sector. What is more, the operation of the Gabëikovo
power plant in peak mode would have occasioned significant daily varia-
tions in the water level in the reservoir upstream, which would have con-
stituted a threat to aquatic habitats in particular. Furthermore, the con-
struction and operation of the Nagymaros dam would have caused the
erosion of the riverbed downstream, along Szentendre Island. The water
level of the river would therefore have fallen in this section and the yield

of the bank-filtered wells providing two-thirds of the water supply of the
city of Budapest would have appreciably diminished. The filter layer
would also have shrunk or perhaps even disappeared, and fine sediments
would have been deposited in certain pockets in the river. For this two-
fold reason, the quality of the infiltrating water would have been severely
jeopardized.
From al1these predictions, in support of which it quoted a variety of
scientific studies, Hungary concluded that a "state of ecological neces-
sitv" did indeed exist in 1989.
41. In its written pleadings, Hungary also accused Czechoslovakia of
having violated various provisions of the 1977Treaty from before 1989
- in particular Articles 15 and 19relating, respectively, to water quality
and nature protection - in refusing to take account of the now evident
ecological dangers and insisting that the works be continued, notably at
Nagymaros. In this context Hungary contended that, in accordance with

the terms of Article 3,paragraph 2, of the Agreement of 6 May 1976con-
cerning the Joint Contractual Plan, Czechoslovakia bore responsibility
for research into the Project's impact on the environment; Hungary
stressed that the research carried out by Czechoslovakia had not been
conducted adequately, the potential effects of the Project on the environ-
ment of the construction having been assessed by Czechoslovakia only
from September 1990.However, in the final stage of its argument, Hun-
gary does not appear to have sought to formulate this complaint as an
independent ground formally justifying the suspension and abandonment
of the works for which it was responsible under the 1977Treaty. Rather,
it presented the violations of the Treaty prior to 1989,which it imputes to
Czechoslovakia, as one of the elements contributing to the emergence of
a state of necessity.

42. Hungary moreover contended from the outset that its conduct in

the present case should not be evaluated only in relation to the law of
treaties. It also observed that, in accordance with the provisions of
Article 4, the Vienna Convention of 23 May 1969on the Law of Treaties
could not be applied to the 1977Treaty, which was concluded before that
Convention entered into force as between the parties. Hungary has
indeed acknowledged, with reference to the jurisprudence of the Court,
that in many respects the Convention reflectsthe existing customary law.
Hungary nonetheless stressed the need to adopt a cautious attitude, while37 GABCIKOVO-NACYMAROS PROJECT (JUDGMENT)

suggesting that the Court should consider, in each case, the conformity of
the prescriptions of the Convention with customary international law.
43. Slovakia, for its part, denied that the basis for suspending or aban-
doning the performance of a treaty obligation can be found outside the

law of treaties. It acknowledged that the 1969 Vienna Convention could
not be applied as such to the 1977 Treaty, but at the same time stressed
that a number of its provisions are a reflection of pre-existing rules of
customary international law and specified that this is, in particular, the
case with the provisions of Part V relating to invalidity, termination and
suspension of the operation of treaties. Slovakia has moreover observed

that, after the Vienna Convention had entered into force for both parties,
Hungary affirmed its accession to the substantive obligations laid down
by the 1977 Treaty when it signed the Protocol of 6 February 1989 that
cut short the schedule of work: and this led it to conclude that the Vienna
Convention was applicable to'the "contractual legal régime"constituted
by the network of interrelated agreements of which the Protocol of 1989

was a part.
44. In the course of the proceedings, Slovakia argued at length that the
state of necessity upon which Hungary relied did not constitute a reason
for the suspension of a treaty obligation recognized by the law of treaties.
At the same time, it cast doubt upon whether "ecological necessity" or
"ecological risk" could, in relation to the law of State responsibility, con-

stitute a circumstance precluding the wrongfulness of an act.
In any event, Slovakia denied that there had been any kind of "eco-
logical state of necessity" in this case either in 1989 or subsequently. It
invoked the authority of various scientific studies when it claimed that
Hungary had given an exaggeratedly pessimistic description of the situa-
tion. Slovakia did not, of course, deny that ecological problems could

have arisen. However, it asserted that they could to a large extent have
been remedied. It accordingly stressed that no agreement had been
reached with respect to the modalities of operation of the GabCikovo
power plant in peak mode, and claimed that the apprehensions of Hun-
gary related only to operating conditions of an extreme kind. In the same
way, it contended that the original Project had undergone various modi-

fications since 1977 and that it would have been possible to modify it
even further, for example with respect to the discharge of water reserved
for the old bed of the Danube, or the supply of water to the side-arms by
means of underwater weirs.
45. Slovakia moreover denied that it in any way breached the 1977
Treaty - particularly its Articles15and 19 - and maintained, inter dia,

that according to the terms of Article 3,paragraph 2,of the Agreement
of 6 May 1976 relating to the Joint Contractual Plan, research into the
impact of the Project on the environment was not the exclusive respon-
sibility of Czechoslovakia but of either one of the parties, depending on
the location of the works.
Lastly, in its turn, it reproached Hungary with having adopted its uni-

lateral measures of suspension and abandonment of the works in viola-tion of the provisions of Article 27 of the 1977Treaty (see paragraph 18
above), which it submits required prior recourse to the machinery for dis-
pute settlement provided for in that Article.

46. The Court has no need to dwell upon the question of the applica-
bility in the present case of the Vienna Convention of 1969on the Law of
Treaties. It needs only to be mindful of the fact that it has several times

had occasion to hold that some of the rules laid down in that Convention
might be considered as a codification of existing customary law. The
Court takes the view that in many respects this applies to the provisions
of the Vienna Convention concerning the termination and the suspension
of the operation of treaties, set forth in Articles 60 to 62 (see Legal Con-
seyuencesfor States ofthe Continued Presence ofSouth Afiicu in Namibia

(South West Ajrica) not1vithstunding Security Council Resolution 276
(1970), Advisory Opinion, I.C.J. Reports. 1971, p. 47, and Fisheries
Jurisdiction (United Kingdom v. Iceland), Jurisdiction of the Court,
Judgment, I.C.J. Reports 1973, p. 18; see also Interpretation qf the
Agreement of 25 Murch 1951 hetitjeen the WHO and Egypt, Advisory

Opinion, 1.C.J. Reports 1980, pp. 95-96).
Neither has the Court lost sight of the fact that the Vienna Convention
is in any event applicable to the Protocol of 6 February 1989 whereby
Hungary and Czechoslovakia agreed to accelerate completion of the
works relating to the GabEikovo-Nagymaros Project.

47. Nor does the Court need to dwell upon the question of the rela-
tionship between the law of treaties and the law of State responsibility, to
which the Parties devoted lengthy arguments, as those two branches of
international law obviously have a scope that is distinct. A determination
of whether a convention is or is not in force, and whether it has or has
not been properly suspended or denounced, is to be made pursuant to the

law of treaties. On the other hand, an evaluation of the extent to which
the suspension or denunciation of a convention, seen as incompatible
with the law of treaties,involves the responsibility of the State which pro-
ceeded to it, is to be made under the law of state responsibility.

Thus the Vienna Convention of 1969 on the Law of Treaties confines
itself to defining- in a limitative manner - the conditions in which a
treaty may lawfully be denounced or suspended; while the effects of a
denunciation or suspension seen as not meeting those conditions are, on
the contrary, expressly excluded from the scope of the Convention by
operation of Article 73. It is moreover well established that, when a State

has committed an internationally wrongful act, its international respon-
sibility is likely to be involved whatever the nature of the obligation it
has failed to respect (cf. Interpretation of Peuce Treaties ivith Bulgaria,
Hungarp and Romania, Second Phase, Advisory Opinion, 1.C.J. Reports
1950, p. 228; and see Article 17 of the Draft Articles on State Responsi-39 GABC~KOVO-NAGYM PA RJOST (JUDGMENT)

bility provisionally adopted by the International Law Commission on
first reading, Yearbook of the International Law Commission, 1980,
Vol. II,Part 2, p. 32).
48. The Court cannot accept Hungary's argument to the effect that, in
1989, in suspending and subsequently abandoning the works for which it

was still responsible at Nagymaros and at Dunakiliti, it did not, for al1
that, suspend the application of the 1977Treaty itself or then reject that
Treaty. The conduct of Hungary at that time can only be interpreted as
an expression of its unwillingness to comply with at least some of the pro-
visions of the Treaty and the Protocol of 6 February 1989, as specified in

the Joint Contractual Plan. The effect of Hungary's conduct was to
render impossible the accomplishment of the system of works that the
Treaty expressly described as "single and indivisible".
The Court moreover observes that, when it invoked the state of neces-
sity in an effort to justify that conduct, Hungary chose to place itself

from the outset within the ambit of the law of State responsibility,
thereby implying that, in the absence of such a circumstance, its conduct
would have been unlawful. The state of necessity claimed by Hungary -
supposing it to have been established- thus could not permit of the con-
clusion that, in 1989, it had acted in accordance with its obligations
under the 1977Treaty or that those obligations had ceased to be binding

upon it. It would only permit the affirmation that, under the circum-
stances, Hungary would not incur international responsibility by acting
as it did. Lastly, the Court points out that Hungary expressly acknow-
ledged that, in any event, such a state of necessity would not exempt it
from its duty to compensate its partner.

49. The Court will now consider the question of whether there was, in
1989, a state of necessity which would have permitted Hungary, without
incurring international responsibility, to suspend and abandon works
that it was committed to perform in accordance with the 1977Treaty and
related instruments.

50. Inthe present case, the Parties are in agreement in considering that
the existence of a state of necessity must be evaluated in the light of the
criteria laid down by the International Law Commission in Article 33 of
the Draft Articles on the International Responsibility of States that it
adopted on first reading. That provision is worded as follows:

"Article33. Stufe of'Necrssify

1. A state of necessity may not be invoked by a State as a ground
for precluding the wrongfulness of an act of that State not in con-
formity with an international obligation of the State unless:

(a) the act was the only means of safeguarding an essential interest
of the State against a grave and imminent peril; and40 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

(6) the act did not seriously impair an essential interest of the State
towards which the obligation existed.
2. In any case, a state of necessity may not be invoked by a State
as a ground for precluding wrongfulness:

(a) if the international obligation with which the act of the State is
not in conformity arises out of a peremptory norm of general
international law; or
(b) if the international obligation with which the act of the State is
not in conformity is laid down by a treaty which, explicitly or
implicitly, excludesthe possibility ofinvoking the state of neces-
sity with respect to that obligation; or
(c) if the State in question has contributed to the occurrence of the
state of necessity." (Yearbook of the International Laiv Com-
mission, 1980, Vol. II, Part 2, p. 34.)

In its Commentary, the Commission defined the "state of necessity" as
being
"the situation of a State whose sole means of safeguarding an essen-
tial interest threatened by a grave and imminent peril is to adopt
conduct not in conformity with what is required of it by an interna-
tional obligation to another State" (ibid., para. 1).

It concluded that "the notion of state of necessity is . . .deeply rooted in
general legal thinking" (ibid, p. 49, para. 31).
51. The Court considers, first of all, that the state of necessity is a
ground recognized by customary international law for precluding the
wrongfulness of an act not in conformity with an international obliga-
tion. It observes moreover that such ground for precluding wrongfulness
can only be accepted on an exceptional basis. The International Law
Commission was of the same opinion when it explained that it had opted
for a negative form of words in Article 33 of its Draft

"in order to show, by this formal means also, that the case of invoca-
tion of a state of necessity as a justification must be considered as
really constituting an exception - and one even more rarely admis-
sible than is the case with the other circumstances precluding wrong-
fulness . . ."(ibid, p. 51, para. 40).

Thus, according to the Commission, the state of necessitycan only be
invoked under certain strictly defined conditions which must be cumula-
tively satisfied; and the State concerned is not the solejudge of whether
those conditions have been met.
52. In the present case, the following basic conditions set forth in
Draft Article 33 are relevant: it must have been occasioned by an "essen-
tial interest" of the State which is the author of the act conficting with
one of its international obligations; that interest must have been threat-
ened by a "grave and imminent peril"; the act being challenged must41 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

have been the "only means" of safeguarding that interest; that act must
not have "seriously impair[ed] an essential interest" of the State towards
which the obligation existed; and the State which is the author of that act
must not have "contributed to the occurrence of the state of necessity".

Those conditions reflect customary international law.
The Court will now endeavour to ascertain whether those conditions
had been met at the time of the suspension and abandonment, by Hun-
gary, of the works that it was to carry out in accordance with the 1977
Treaty.
53. The Court has no difficulty in acknowledging that the concerns

expressed by Hungary for its natural environment in the region affected
by the Gabtikovo-Nagymaros Project related to an "essential interest" of
that State, within the meaning given to that expression in Article 33 of
the Draft of the International Law Commission.

The Commission, in its Commentary, indicated that one should not, in

that context, reduce an "essential interest" to a matter only of the "exist-
ence" of the State, and that the whole question was, ultimately, to be
judged in the light of the particular case (see Yeurbook of the Internu-
tionul Luiv Commission, 1980, Vol. II, Part 2, p. 49, para. 32); at the
same time, it included among the situations that could occasion a state of
necessity, "a grave danger to . . . the ecological preservation of al1 or

some of [the] territory [of a State]" (ibid, p. 35, para. 3); and specified,
with reference to State practice, that "It is primarily in the last two
decades that safeguarding the ecological balance has come to be con-
sidered an 'essential interest' of al1States." (Ibid., p. 39, para. 14.)

The Court recalls that it has recently had occasion to stress, in thefol-
lowing terms, the great significance that it attaches to respect for the envi-
ronment, not only for States but also for the whole of mankind:

"the environment is not an abstraction but represents the living
space, the quality of life and the very health of human beings,
including generations unborn. The existence of the general obliga-
tion of States to ensure that activities within their jurisdiction and

control respect the environment of other States or of areas beyond
national control is now part of the corpus of international law relat-
ing to the environment." (Legality of the Threut or Use of Nuclear
Weapons, Advisoty Opinion, I.C. J. Reports 1996, pp. 241-242,
para. 29.)

54. The verification of the existence, in 1989, of the "peril" invoked by
Hungary, of its "grave and imminent" nature, as well as of the absence of
any "means" to respond to it, other than the measures taken by Hungary

to suspend and abandon the works, are al1complex processes.42 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

As the Court has already indicated (see paragraphs 33 et seq.),
Hungary on several occasions expressed, in 1989,its "uncertainties" as to
the ecological impact of putting in place the GabCikovo-Nagymaros bar-
rage system, which is why it asked insistently for new scientific studies to

be carried out.

The Court considers, however, that, serious though these uncertainties
might have been they could not, alone, establish the objective existence of
a "peril" in the sense of a component element of a state of necessity. The

word "Deril" certainlv evokes the idea of "risk": that is vreciselv what
distinguishes "peril" from material damage. But a state of necessity could
not exist without a "Deril" dulv established at the relevant oint in time:
the mere apprehensi'on of a Possible "peril" could not Affice in that
remect. It could moreover hardlv be otherwise. when the "~eril" consti-
tuting the state of necessity has at the same time to be "grave" and

"imminent". "Imminence" is synonymous with "immediacy" or "proxim-
ity" and goes far beyond the concept of "possibility". As the Interna-
tional Law Commission em~hasized in its commentarv. the "ex,,emelv
grave and imminent" peril must "have been a threat to the interest at
the actual time" (Yearbook of the International Laiv Commission, 1980,
Vol. II, Part 2, p. 49, para. 33). That does not exclude, in the view of the

Court, that a "peril" appearing in the long term might be held to be
"imminent" as soon as it is established, at the relevant point in time, that
the realization of that peril, however far off it might be, is not thereby
any less certain and inevitable.
The Hungarian argument on the state of necessity could not convince
the Court unless it was at least proven that a real, "grave" and "immi-

nent" "peril" existed in 1989 and that the measures taken by Hungary
were the only possible response to it.
Both Parties have placed on record an impressive amount of scientific
material aimed at reinforcing their respective arguments. The Court has
given most careful attention to this material, in which the Parties have

developed their opposing views as to the ecological consequences of the
Project. It concludes, however, that, as will be shown below, it is not
necessary in order to respond to the questions put to it in the Special
Agreement for it to determine which of those points of view is scienti-
fically better founded.
55. The Court will begin by considering the situation at Nagymaros.

As has already been mentioned (see paragraph 40), Hungary maintained
that, if the works at Nagymaros had been carried out as planned, the
environment - and in particular the drinking water resources - in the
area would have been exposed to serious dangers on account of problems
linked to the upstream reservoir on the one hand and, on the other, the
risks of erosion of the riverbed downstream.

The Court notes that the dangers ascribed to the upstream reservoir
were mostly of a long-term nature and, above all, that they remained un-
certain. Even though the Joint Contractual Plan envisaged that the Gab-Eikovo power plant would "mainly operate in peak-load time and con-

tinuously during high water", the final rules of operation had not yet
been determined (see paragraph 19 above); however, any dangers asso-
ciated with the putting into service of the Nagymaros portion of the
Project would have been closely linked to the extent to which it was oper-
ated in peak mode and to the modalities of such operation. It follows

that, even if it could have been established - which, in the Court's
appreciation of the evidence before it, was not the case - that the reser-
voir would ultimately have constituted a "grave peril" for the environ-
ment in the area, one would be bound to conclude that the peril was not
"imminent" at the time at which Hungary suspended and then aban-

doned the works relating to the dam.

With regard to the lowering of the riverbed downstream of the Nagy-
maros dam, the danger could have appeared at once more serious and
more pressing, in so far as it was the supply of drinking water to the city

of Budapest which would have been affected. The Court would however
point out that the bed of the Danube in the vicinity of Szentendre had
already been deepened prior to 1980 in order to extract building mater-
ials, and that the river had from that time attained, in that sector, the
depth required by the 1977 Treaty. The peril invoked by Hungary had

thus already materialized to a large extent for a number of years, so that
it could not, in 1989,represent a peril arising entirely out of the project.
The Court would stress, however, that, even supposing, as Hungary
maintained, that the construction and operation of the dam would have
created serious risks, Hungary had means available to it, other than the

suspension and abandonment of the works, of responding to that situa-
tion. It could for example have proceeded regularly to discharge grave1
into the river downstream of the dam. It could likewise, if necessary, have
supplied Budapest with drinking water by processing the river water in
an appropriate manner. The two Parties expressly recognized that that

possibility remained open even though - and this is not determinative of
the state of necessity - the purification of the river water, like the other
measures envisaged, clearly would have been a more costly technique.

56. The Court now comes to the GabEikovo sector. It will recall that

Hungary's concerns in this sector related on the one hand to the quality
of the surface water in the Dunakiliti reservoir, with its effects on the
quality of the groundwater in the region, and on the other hand, more
generally, to the level, movement and quality of both the surface water

and the groundwater in the whole of the Szigetkoz, with their effects on
the Sauna and flora in the alluvial plain of the Danube (see paragraph 40
above).
Whether in relation to the Dunakiliti site or to the whole of the
Szigetkoz, the Court finds here again, that the peril claimed by Hungary
was to be considered in the long term, and, more importantly, remained

uncertain. As Hungary itself acknowledges, the damage that it appre-44 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

hended had primarily to be the result of some relatively slow natural
processes, the effects of which could not easily be assessed.
Even if the works were more advanced in this sector than at Nagy-
maros, they had not been completed in July 1989 and, as the Court

explained in paragraph 34 above, Hungary expressly undertook to carry
on with them, early in June 1989. The report dated 23 June 1989 by the
ud hoc Committee of the Hungarian Academy of Sciences, which was
also referred to in paragraph 35 of the present Judgment, does not
express any awareness of an authenticated peril - even in the form of a

definite peril, whose realization would have been inevitable in the long
term - when it States that:
"The measuring results of an at least five-year monitoring period

following the completion of the Gabtikovo construction are indis-
pensable to the trustworthy prognosis of the ecological impacts of
the barrage system. There is undoubtedly a need for the establish-
ment and regular operation of a comprehensive monitoring system,
which must be more developed than at present. The examination of

biological indicatorobjects that can sensitively indicate the changes
happening in the environment, neglected till today, have to be
included."

The report concludes as follows:

"It can be stated, that the environmental, ecological and water
quality impacts were not taken into account properly during the
design and construction period until today. Because of the complex-
ity of the ecological processes and lack of the measured data and the
relevant calculations the environmental impacts cannot be evalu-
ated.

The data of the monitoring system newly operating on a very lim-
ited area are not enough to forecast the impacts probably occurring
over a longer term. In order to widen and to make the data more
frequent a further multi-year examination is necessary to decrease
the further degradation of the water quality playing a dominant role
in this question. The expected water quality influences equally the

aquatic ecosystems, the soils and the recreational and tourist
land-use."

The Court also notes that, in these proceedings, Hungary acknowledged
that, as a general rule, the quality of the Danube waters had improved
over the past 20 years, even if those waters remained subject to hyper-
trophic conditions.
However "grave" it might have been, it would accordingly have been

difficult, in the light of what is said above, to see the alleged peril as suf-
ficiently certain and therefore "imminent" in 1989.
The Court moreover considers that Hungary could, in this context45 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

also, have resorted to other means in order to respond to the dangers that
it apprehended. In particular, within the framework of the original
Project, Hungary seemed to be in a position to control at least partially
the distribution of the water between the bypass canal, the old bed of the

Danubeand the side-arms. It should not be overlooked that the Dunakiliti
dam was located in Hungarian territory and that Hungary could con-
struct the works needed to regulate flows along the old bed of the Dan-
ube and the side-arms. Moreover, it should be borne in mind that
Article 14 of the 1977Treaty provided for the possibility that each of the

parties might withdraw quantities of water exceeding those specified in
the Joint Contractual Plan, while making it clear that, in such an event,
"the share of electric power of the Contracting Party benefiting from the
excess withdrawal shall be correspondingly reduced".
57. The Court concludes from the foregoing that, with respect to both

Nagymaros and GabCikovo, the perils invoked by Hungary, without pre-
judging their possible gravity, were not sufficiently established in 1989,
nor were they "imminent"; and that Hungary had available to it at that
time means of responding to these perceived perils other than the suspen-
sion and abandonment of works with which it had been entrusted. What

is more, negotiations were under way which might have led to a review of
the Project and the extension of some of its time-limits, without there
being need to abandon it. The Court infers from this that the respect by
Hungary, in 1989, of its obligations under the terms of the 1977 Treaty
would not have resulted in a situation "characterized so aptly by the

maxim summum jus summa injuria" (Yearbook of the International Law
Commission, 1980, Vol. II, Part 2, p. 49, para. 31).
Moreover, the Court notes that Hungary decided to conclude the 1977
Treaty, a Treaty which - whatever the political circumstances prevailing
at the time of its conclusion - was treated by Hungary as valid and in
force until the date declared for its termination in May 1992. As can be

seen from the material before the Court, a great many studies of a scien-
tific and technical nature had been conducted at an earlier time, both by
Hungary and by Czechoslovakia. Hungary was, then, presumably aware
of the situation as then known, when it assumed its obligations under the
Treaty. Hungary contended before the Court that those studies had been

inadequate and that the state of knowledge at that time was not such as
to make possible a complete evaluation of the ecological implications of
the GabCikovo-Nagymaros Project. It is nonetheless the case that
although the principal object of the 1977Treaty was the construction of
a System of Locks for the production of electricity, improvement of navi-

gation on the Danubeand protection against flooding, the need to ensure
the protection of the environment had not escaped the parties, as can be
seen from Articles 15, 19 and 20 of the Treaty.

What is more, the Court cannot fail to note the positions taken by
Hungary after the entry into force of the 1977Treaty. In 1983, Hungary

asked that the works under the Treaty should go forward more slowly,46 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

for reasons that were essentially economic but also, subsidiarily, related
to ecological concerns. In 1989, when, according to Hungary itself, the
state of scientific knowledge had undergone a significant development, it
asked for the works to be speeded up, and then decided, three months
later, to suspend them and subsequently to abandon them. The Court is
not however unaware that profound changes were taking place in Hun-

gary in 1989, and that, during that transitory phase, it might have been
more than usually difficult to co-ordinate the different points of view pre-
vailing from time to time.
The Court infers from al1these elements that, in the present case, even
if it had been established that there was. in 1989, a state of necessity
linked to the performance of the 1977 Treaty, Hungary would not have

been permitted to rely upon that state of necessity in order to justify its
failure to comply with its treaty obligations, as it had helped, by act or
omission to bring it about.
58. It follows that the Court has no need to consider whether Hun-
gary, by proceeding as it did in 1989, "seriously impair[ed] an essential
interest" of Czechoslovakia, within the meaning of the aforementioned
Article 33 of the Draft of the International Law Commission - a finding

which does not in any way prejudge the damage Czechoslovakia claims
to have suffered on account of the position taken by Hungary.
Nor does the Court need to examine the argument put forward by
Hungary, according to which certain breaches of Articles 15 and 19 of
the 1977 Treaty, committed by Czechoslovakia even before 1989, con-
tributed to the purported state of necessity; and neither does it have to

reach a decision on the argument advanced by Slovakia, according to
which Hungary breached the provisions of Article 27 of the Treaty,
in 1989, by taking unilateral measures without having previously
had recourse to the machinery of dispute settlement for which that
Article provides.

59. In the light of the conclusions reached above, the Court, in reply to
the question put to it in Articl2, paragraph 1 (a), of the Special Agree-
ment (see paragraph 27 above), finds that Hungary was not entitled to
suspend and subsequently abandon, in 1989, the works on the Nagy-
maros Project and on the part of the GabEikovo Project for which the
1977 Treaty and related instruments attributed responsibility to it.

60. By the terms of Article 2, paragraph 1 (h),of the Special Agree-
ment, the Court is asked in the second place to decide

"(6) whether the Czech and Slovak Federal Republic was entitled
to proceed, in November 1991, to the 'provisional solution' GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

and to put into operation from October 1992 this system,
described in the Report of the Working Group of Independent
Experts of the Commission of the European Communities, the
Republic of Hungary and the Czech and SlovakFederal Repub-

lic dated 23 November 1992 (damming up of the Danube at
river kilometre 1851.7 on Czechoslovak territory and resulting
consequences on water and navigation course)".

61. The Court will recall that, as soon as Hungary suspended the
works at Nagymaros on 13 May 1989 and extended that suspension to
certain works to be carried out at Dunakiliti, Czechoslovakia informed
Hungary that it would feel compelled to take unilateral measures if Hun-

gary were to persist in its refusa1to resume the works. This was inter alia
expressed as follows in Czechoslovakia's Note Verbale of 30 October
1989 to which reference is made in paragraph 37 above:

"Should the Republic of Hungary fail to meet its liabilities and
continue unilaterally to breach the Treaty and related legal docu-
ments then the Czechoslovak party will be forced to commence a

provisional, substitute project on the territory of the Czechoslovak
Socialist Republic inorder to prevent further losses. Such a provi-
sional project would entail directing as much water into the Gab-
tikovo dam as agreed in the Joint Construction Plan."

As the Court has already indicated (see paragraph 23), various
alternative solutions were contemplated by Czechoslovakia. In Septem-
ber 1990, the Hungarian authorities were advised of seven hypothetical

alternatives defined by the firm of Hydroconsult of Bratislava. All of
those solutions implied an agreement between the parties, with the excep-
tion of one variant, subsequently known as "Variant C", which was pre-
sented as a provisional solution which could be brought about without
Hungarian CO-operation. Other contacts between the parties took place,
without leading to a settlement of the dispute. In March 1991, Hungary

acquired information according to which perceptible progress had been
made in finalizing the planning of Variant C; it immediately gave expres-
sion to the concern this caused.
62. Inter-governmental negotiation meetings were held on 22 April
and 15 July 1991.
On 22 April 1991, Hungary proposed the suspension, until September

1993, of al1 the works begun on the basis of the 1977 Treaty, on the
understanding that the parties undertook to abstain from any unilateral
action, and that joint studies would be carried out in the interval.
Czechoslovakia maintained its previous position according to which the
studies contemplated should take place within the framework of the 1977
Treaty and without any suspension of the works.

On 15July 1991,Czechoslovakia confirmed its intention of putting the48 GAB~IKOVO-NAGYMAROS PROJECT (JUDGMENT)

GabEikovo power plant into service and indicated that the available data
enabled the effects of four possible scenarios to be assessed, each of them
requiring the co-operation of the two Governments. At the same time, it
proposed the setting up of a tripartite committee of experts (Hungary,
Czechoslovakia, European Communities) which would help in the search
for technical solutions to the problems arising from the entry into opera-
tion of the GabCikovo sector. Hungary, for its part, took the view that :

"In the case of a total lack of understanding the so-called C varia-
tion or 'theoretical opportunity' suggested by the Czecho-Slovak
party as a unilateral solution would besuch a grave transgression of
Hungarian territorial integrity and International Law for which
there is no precedent even in the practices of the formerly socialist
countries for the past 30 years";

it further proposed the setting up of a bilateral committee for the assess-
ment of environmental consequences, subject to work on Czechoslovak
territory being suspended.
63. By a letter dated 24 July 1991,the Government of Hungary com-
municated the following message to the Prime Minister of Slovakia:
"Hungarian public opinion and the Hungarian Government

anxiously and attentively follows the [Czechoslovakian] press reports
of the unilateral steps of the Government of the Slovak Republic
in connection with the barrage system.
The preparatory works for diverting the water of the Danube near
the Dunakiliti dam through unilaterally are also alarming. These
steps are contrary to the 1977Treaty and to the good relationship
between our nations."

On 30 July 1991 the Slovak Prime Minister informed the Hungarian
Prime Minister of
"the decision of the Slovak Government and of the Czech and Slo-
vak Federal Government to continue work on the GabEikovo power
plant, as a provisional solution, which is aimed at the commence-
ment of operations on the territory of the Czech and Slovak Federal
Republic".

On the same day, the Government of Hungary protested, by a Note Ver-
bale, against the filling of the headrace canal by the Czechoslovak con-
struction Company, by pumping water from the Danube.
By aletter dated 9 August 1991and addressed to the Prime Minister of
Slovakia, the Hungarian authorities strenuously protested against "any
unilateral step that would be in contradiction with the interests of our
[two]nations and international law" and indicated that they considered it
"very important [to] receive information as early as possible on the49 GABC~KOVO-NAGYM PROJOCT (JUDGMENT)

details of the provisional solution".For its part, Czechoslovakia, in a
Note Verbale dated 27 August 1991, rejected the argument of Hungary
that the continuation of the works under those circumstances constituted
a violation of international law, and made the following proposal:

"Provided the Hungarian side submits a concrete technical solu-
tion aimed at putting into operation theabtikovo system of locks

and a solution of the system of locks based on the 1977 Treaty in
force and the treaty documents related to it, the Czechoslovak side is
prepared to implement the mutually agreed solution."

64. The construction permit for Variant C was issued Gn 30 October
1991.In November 1991construction of a dam started at Cunovo, where
both banks of the Danube are on Czechoslovak (now Slovak) territory.

In the course of a new inter-governmental negotiation meeting, on

2 December 1991, the parties agreed to entrust the task of studying the
whole of the question of the Gabtikovo-Nagymaros Project to a Joint
Expert Committee which Hungary agreed should be complemented with
an expert from the European Communities. However whereas, for Hun-
gary,the work of that Committee would have been meaningless if Czecho-

slovakia continued construction of Variant C, for Czechoslovakia, the
suspension of the construction, even on a temporary basis, was unaccept-
able.
That meeting was followed by a large number of exchanges of letters
between the parties and various meetings between their representatives at

the end of 1991 and earlv in 1992. On 23 Januarv 1992. Czechoslovakia
expressed its readiness "to stop work on the provisional solution and
continue the construction upon mutual agreement" if the tripartite com-
mittee of experts whose constitution it proposed, and the results of the
test operation of the GabCikovo part, were to "confirm that negative eco-
logical effects exceed its benefits". However, the positions of the parties

were by then comprehensively defined, and would scarcely develop any
further. Hungary considered, as it indicated in a Note Verbale of 14 Feb-
ruary 1992, that Variant C was in contravention

"of [the Treaty of 19771. . . and the convention ratified in 1976
regarding the water management of boundary waters.

.............................
with the principles of sovereignty, territorial integrity, with the
inviolability of State borders, as well as with the general customary
norms on international rivers and the spirit of the 1948 Belgrade
Danube Convention" ;

and the suspension of the implementation of Variant C was, in its view, a
prerequisite. As for Czechoslovakia, it took the view that recourse to
Variant C had been rendered inevitable, both for economic and ecologi-cal as well as navigational reasons, because of the unlawful suspension
and abandonment by Hungary of the works for which provision was
made in the 1977 Treaty. Any negotiation had, in its view, to be con-
ducted within the framework of the Treaty and without the implementa-
tion of Variant C - described as "provisional" - being called into

question.
65. On 5 August 1992,the Czechoslovak representative to the Danube
Commission informed it that "work on the severance cutting through of
the Danube's flow will begin on 15 October 1992 at the 1,851.759-kilo-
metre line" and indicated the measures that would be taken at the time of
the "severance". The Hungarian representative on the Commission pro-

tested on 17 August 1992, and called for additional explanations.
During the autumn of 1992, the implementation of VariantvC was
stepped up. The operations involved in damming the Danube at Cunovo
had been scheduled by Czechoslovakia to take place during the second
half of October 1992,at a time when the waters of the river are generally
at their lowest level. On the initiative of the Commission of the European

Communities, trilateral negotiations took place in Brussels on 21 and
22 October 1992, with a view to setting up a committee of experts and
defining its terms of reference. On that date, the first phase of the opera-
tions leading to the damming of the Danube (the reinforcement of the
riverbed and the narrowing of the principal channel) had been com-
pleted. The closure of the bed was begun on 23 October 1992 and the

construction of the actual dam continued from 24 to 27 October 1992:
a pontoon bridge was built over the Danube on Czechoslovak territory
using river barges, large Stones were thrown into the riverbed and
reinforced with concrete, while 80 to 90 per cent of the waters of the
Danube were directed into the canal designed to supply the Gabtikovo
power plant. The implementation of Variant C did not, however, come

to an end with the diversion of the waters, as there still remained out-
standing both reinforcement work on the dam and the building of certain
auxiliary structures.
The Court has already referred in paragraph 24 to the meeting
held in London on 28 October 1992 under the auspices of the European
Communities, in the course of which the parties to the negotiations

agreed, inter dia, to entrust a tripartite Working Group composed of
independent experts (Le., four experts designated by the European Com-
mission, one designated by Hungary and another by Czechoslovakia)
with the task of reviewing the situation created by the implementation of
Variant C and making proposals as to urgent measures to adopt. After

having worked for one week in Bratislava and one week in Budapest, the
Working Group filed its report on 23 November 1992.
66. A summary description of the constituent elements of Variant C
appears at paragraph 23 of the present Judgment. For the purposes of
the question put to the Court, the officia1 description that should be
adopted is, according to Article 2, paragraph 1 (b), of the Special Agree-
ment, the one given in the aforementioned report of the Working Group51 GAB~IKOVO-NAGYMAROS PROJECT (JUDGMENT)

of independent experts, and it should be emphasized that, according to
the Special Agreement, "Variant C" must be taken to include the conse-

quences "on water and navigation course" of the dam closing off the bed
of the Danube.
In the section headed "Variant C Structures and Status of Ongoing
Work", one finds, in the report of the W.orking Group, the following
passage :

"In both countries the original structures for the GabEikovo
scheme are completed except for the closure of the Danube river at
Dunakiliti and the
(1) Completion of the hydropower station (installation and testing

of turbines) at GabEikovo.
Variant C consists of a complex of structures, located in Czecho-
Slovakia . . .The construction of these are planned for two phases.
The structures include . . :

(2) By-pass weir controlling the flow into the river Danube.
(3) Dam closing the Danubian river bed.
(4) Floodplain weir (weir in the inundation).
(5) lntake structure for the Mosoni Danube.
(6) lntake structure in the power canal.
(7) Earth barragesidykes connecting structures.

(8) Ship lock for smaller ships (1 5 m x 80 m).
(9) Spillway weir.
(10) Hydropower station.
The construction of the structures 1-7 are included in Phase 1,
while the remaining 8-10 are a part of Phase 2 scheduled for con-

struction 1993-1995."

67. Czechoslovakia had maintained that proceeding to Variant C and
putting it into operation did not constitute internationally wrongful acts;
Slovakia adopted this argument. During the proceedings before the Court
Slovakia contended that Hungary's decision to suspend and subsequently
abandon the construction of works at Dunakiliti had made it impossible
for Czechoslovakia to carry out the works as initially contemplated by

the 1977Treaty and that the latter was therefore entitled to proceed with
a solution which was as close to the original Project as possible. Slovakia
invoked what it described as a "principle of approximate application" to
justify the construction and operation of Variant C. It explained that this
was the only possibility remaining to it "of fulfilling not only the pur-
poses of the 1977Treaty, but the continuing obligation to implement it in
good faith".

68. Slovakia also maintained that Czechoslovakia was under a duty to
mitigate the damage resulting from Hungary's unlawful actions. It claimed52 GABC~KOVO-NAGYM PAORJCST(JUDGMENT)

that a State which is confronted with a wrongful act of another State is

under an obligation to minimize its losses and, thereby, the damages
claimable against the wrongdoing State.It arguedfurthermore that "Miti-
gation of damages is also an aspect of the performance of obligations in
good faith." For Slovakia, these damages would have been immense in
the present case, given the investments made and the additional economic

and environmental prejudice which would have resulted from the failure
to complete the works at DunakilitiiGabEikovo and to put the system
into operation. For this reason, Czechoslovakia was not only entitled,
but even obliged, to implement Variant C.

69. Although Slovakia maintained that Czechoslovakia's conduct was
lawful, it argued in the alternative that, even were the Court to find
otherwise, the putting into operation of Variant C could still be justified
as a countermeasure.

70. Hungary for its part contended that Variant C was a material
breach of the 1977 Treaty. It considered that Variant C also violated
Czechoslovakia's obligations under other treaties, in particular the Con-
vention of 31 May 1976 on the Regulation of Water Management Issues
of Boundary Waters concluded at Budapest, and its obligations under
general international law.

71. Hungary contended that Slovakia's arguments rested on an erro-
neous presentation of the facts and the law. Hungary denied, inter alia,
having committed the slightest violation of its treaty obligations which
could have justified the putting into operation of Variant C. It considered
that "no such rule" of "approximate application" of a treaty exists in

international law; as to the argument derived from "mitigation of dam-
age[s]", it claimed that this has to do with the quantification of loss, and
could not serve to excuse conduct which is substantively unlawful. Hun-
gary furthermore stated that Variant C did not satisfy the conditions
required by international law for countermeasures, in particular the con-

dition of proportionality.

72. Before dealing with the arguments advanced by the Parties, the
Court wishes to make clear that it is aware of theerious problems with

which Czechoslovakia was confronted as a result of Hungary's decision
to relinquish most of the constructionof the System of Locks for which
it was responsible by virtue of the 1977 Treaty. Vast investments had
been made, the construction at GabEikovo was al1 but finished, the
bypass canal was completed, and Hungary itself, in 1991, had duly ful-

filled its obligations under the Treaty in this respect in completing work
on the tailrace canal. It emerges from the report, dated 31 October 1992,
of the tripartite fact-finding mission the Court has referred to in para-
graph 24 of the present Judgment, that not using the system would have53 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

led to considerable financial losses, and that it could have given rise to
serious problems for the environment.
73. Czechoslovakia repeatedly denounced Hungary's suspension and
abandonment of works as a fundamental breach of the 1977 Treaty and

consequently could have invoked this breach as a ground for terminating
the Treaty; but this would not have brought the Project any nearer to
completion. It therefore chose to insist on the implementation of the
Treaty by Hungary, and on many occasions called upon the latter to
resume performance of its obligations under the Treaty.

When Hungary steadfastly refused to do so - although it had expressed
its willingness to pay compensation for damage incurred by Czechoslo-
vakia - and when negotiations stalled owing to the diametrically opposed
positions of the parties, Czechoslovakia decided to put the GabEikovo
system into operation unilaterally, exclusively under its own control and

for its own benefit.
74. That decision went through various stages and, in the Special
Agreement, the Parties asked the Court to decide whether Czecho-
slovakia "was entitled to proceed, in November 1991" to Variant C,
and "to put [it] into operation from October 1992".

75. With a view to justifying those actions, Slovakia invoked what it
described as "the principle of approximate application", expressed by
Judge Sir Hersch Lauterpacht in the following terms:

"lt is a sound principle of law that whenever a legal instrument of
continuing validity cannot be applied literally owing to the conduct of
one of the parties, it must, without allowing that party to take advan-
tage of its own conduct, be applied in a way approximating most

closely to its primary object. To do that is to interpret and to give
effect to the instrument - not to change it." (Adrrzissibilituf Heur-
ings of Petitioners by the Committee on Soutlz West Africu, I.C.J.
Reports 1956, separate opinion of Sir Hersch Lauterpacht, p. 46.)

It claimed that this is a principle of international law and a general prin-
ciple of law.
76. It is not necessary for the Court to determine whether there is a

principle of international law or a general principle of law of "approxi-
mate application" because, even if such a principle existed, it could by
definition only be employed within the limits of the treaty in question. In
the view of the Court, Variant C does not meet that cardinal condition
with regard to the 1977 Treaty.

77. As the Court has already observed, the basic characteristic of the
1977 Treaty is, according to Article 1, to provide for the construction of
the Gabcikovo-Nagymaros System of Locks as a joint investment con-
stituting a single and indivisible operational system of works. This
element is equally reflected in Articles 8 and 10 of the Treaty providing

for joint ownership of the most important works of the GabEikovo-
Nagymaros Project and for the operation of this joint property as a
CO-ordinated single unit. By definition al1 this could not be carried 54 GABCIKOVO-NAGYMAROS PROJECT (JCDGMENT)

out by unilateral action. In spite of having a certain external physical

similarity with the original Project, Variant C thus differed sharply from
it in its legal characteristics.
78. Moreover, in practice, the operation of Variant C led Czechoslo-
vakia to appropriate, essentially for its use and benefit, between 80 and
90 per cent of the waters of the Danube before returning them to the

main bed of the river, despite the fact that the Danube is not only a
shared international watercourse but also an international boundary
river.
Czechoslovakia submitted that Variant C was essentially no more than
what Hungary had already agreed to and that the only modifications
made were those which had become necessary by virtue of Hungary's

decision not to implement its treaty obligations. It is true that Hungary,
in concludingthe 1977Treaty, had agreed to the damming of the Danube
and the diversion of its waters into the bypass canal. But it was only in
the context of a joint operation and a sharing of its benefits that Hungary
had given its consent. The suspension and withdrawal of that consent
constituted a violation of Hungary's legal obligations, demonstrating, as

it did, the refusal by Hungary of joint operation; but that cannot mean
that Hungary forfeited its basic right to an equitable and reasonable
sharing of the resources of an international watercourse.

The Court accordingly concludes that Czechoslovakia, in putting
Variant C into operation, was not applying the 1977 Treaty but, on the

contrary, violated certain of its express provisions, and, in so doing,
committed an internationally wrongful act.
79. The Court notes that between November 1991and October 1992,
Czechoslovakia confined itself to the execution, on its own territory, of
the works which were necessary for the implementation of Variant C, but

which could have been abandoned if an agreement had been reached
between the parties and did not therefore predetermine the final decision
to be taken. For as long as the Danube had not been unilaterally
dammed, Variant C had not in fact been applied.
Such a situation is not unusual in international law or, for that matter,
in domestic law. A wrongful act or offence is frequently preceded by pre-

paratory actions which are not to be confused with the act or offence
itself. It is as well to distinguish between the actual commission of a
wrongful act (whether instantaneous or continuous) and the conduct
prior to that act which is of a preparatory character and which "does
not qualify as a wrongful act" (see for example the Commentary on
Article 41 of the Draft Articles on State Responsibility, "Report of the

International Law Commission on the work of its forty-eighth session,
6 May-26 July 1996", Officiul Records ofthe General Assemblj>, Fifty-
first Session, Supplemcnt No. 10 (AlSlilO), p. 141, and Yearbook of the
International Law Commission, 1993, Vol. II, Part 2, p. 57, para. 14).55 GAB~IKOVO-NAGYMAROS PROJECT (JUDGMENT)

80. Slovakia also maintained that it was acting under a duty to miti-
gate damages when it carried out Variant C. It stated that "It is a general
principle of international law that a party injured by the non-perform-
ance of another contract party must seek to mitigate the damage he has
sustained."
It would follow from such a principle that an injured State which has

failed to take the necessary measures to limit the damage sustained would
not be entitled to claim compensation for that damage which could have
been avoided. While this principle might thus provide a basis for the cal-
culation of damages, it could not, on the other hand, justify an otherwise
wrongful act.
81. Since the Court has found that the putting into operation of Vari-

ant C constituted an internationally wrongful act, the duty to mitigate
damage invoked by Slovakia does not need to be examined further.

82. Although it did not invoke the plea of countermeasures as a
primary argument, since it did not consider Variant C to be unlawful,
Slovakia stated that "Variant C could be presented as a justified
countermeasure to Hungary's illegal acts".

The Court has concluded, in paragraph 78 above, that Czechoslovakia
committed an internationally wrongful act in putting Variant C into
operation. Thus, it now has to determine whether such wrongfulness may
be precluded on the ground that the measure so adopted was in response
to Hungary's prior failure to comply with its obligations under interna-

tional law.
83. In order to be justifiable, a countermeasure must meet certain con-
ditions (see Militurq und Paramilitary Acti~,itie.sin und uguinst Nicara-
gua jNicaraguu v. United Stute~ of Anwrica) , Merits, Judgment, 1.C.J.
Reports 1986. p. 127, para. 249. See also Arbitral Abvardoj 9 Dccrmher
19711in the case concerning the Air Service Agreement oj 27 Murch 1946

betwern the Unitrd States oj America and France, United Nations,
Reports of lnternutionul Arbitral A)t,ards (RIAA), Vol. XVIII, pp. 443 et
seq.; also Articles 47 to50 of the Draft Articles on State Responsibility
adopted by the International Law Commission on first reading, "Report
of the International Law Commission on the work of its forty-eighth ses-
sion, 6 May-26 July 1996", Ofjciul Records of the General Assembly,

Fifty-Jirst Session, Supplement No. 10 (A/51110),pp. 144-145.)

In the first place it must be taken in response to a previous interna-
tional wrongful act of another State and must be directed against that
State. Although not primarily presented as a countermeasure, it is clear
that Variant C was a response to Hungary's suspension and abandon-ment of works and that it was directed against that State; and it is
equally clear, in the Court's view, that Hungary's actions were interna-
tionally wrongful.
84. Secondly, the injured State must have called upon the State com-
mitting the wrongful act to discontinue its wrongful conduct or to make
reparation for it. It is clear from the facts of the case, as recalled above by

the Court (see paragraphs 61 et seq.), that Czechoslovakia requested
Hungary to resume the performance of its treaty obligations on many
occasions.
85. In the view of the Court, an important consideration is that the
effects of a countermeasure must be commensurate with the injury suf-

fered, taking account of the rights in question.
In 1929, the Permanent Court of International Justice, with regard to
navigation on the River Oder, stated as follows:

"[the] community of interest in a navigable river becomes the basis
of a common legal right, the essential features of which are the per-

fect equality of al1riparian States in the user of the whole course of
the river and the exclusion of any preferential privilege of any one
riparian State in relation to the others" (Territorial Jurisdiction of
the International Commission of the River Oder, Judgment No. 16,
1929, P.C.I.J., Series A, No. 23, p. 27).

Modern development of international law has strengthened this prin-
ciple for non-navigational uses of international watercourses as well, as
evidenced by the adoption of the Convention of 21 May 1997on the Law
of the Non-Navigational Uses of International Watercourses by the
United Nations General Assembly.

The Court considers that Czechoslovakia, by unilaterally assuming
control of a shared resource, and thereby depriving Hungary of its right
to an equitable and reasonable share of the natural resources of the Dan-
ube - with the continuing effects of the diversion of these waters on the
ecology of the riparian area of the Szigetkoz - failed to respect the pro-
portionality which is required by international law.

86. Moreover, as the Court has already pointed out (see para-
graph 78), the fact that Hungary had agreed in the context of the original
Project to the diversion of the Danube (and, in the Joint Contractual
Plan, to a provisional measure of withdrawal of water from the Danube)
cannot be understood as having authorized Czechoslovakia to proceed
with a unilateral diversion of this magnitude without Hungary's consent.

87. The Court thus considers that the diversion of the Danube carried
out by Czechoslovakia was not a lawful countermeasure because it was
not proportionate. It is therefore not required to pass upon one other
condition forthe lawfulness of a countermeasure, namely that its purpose
must be to induce the wrongdoing State to comply with its obliga-57 GAB~~KOVO-NAGYMAROSPROJECT (JUDGMENT)

tions under international law, and that the measure must therefore be
reversible.

88. In the light of the conclusions reached above, the Court, in reply to
the question put to it in Article 2, paragraph 1 (h), of the Special Agree-
ment (see paragraph 60), finds that Czechoslovakia was entitled to pro-
ceed, in November 1991, to Variant C in so far as it then confined itself

to undertaking works which did not predetermine the final decision to be
taken by it. On the other hand, Czechoslovakia was not entitled to put
that Variant into operation from October 1992.

89. By the terms of Article 2, paragraph 1 (c), of the Special Agree-
ment, the Court is asked, thirdly, to determine "what are the legal effects
of the notification, on 19 May 1992, of the termination of the Treaty by
the Republic of Hungary".

The Court notes that it has been asked to determine what are the legal
effects of the notificatioG drivenon 19Mav 1992of the termination of the
Treaty. It will consequently confine itself to replying to this question.
90. The Court will recall that, by early 1992, the respective parties to
the 1977Treaty had made clear their positions with regard to the recourse

by Czechoslovakia to Variant C. Hungary in a Note Verbale of 14 Feb-
ruary 1992had made clear its view that Variant C was a contravention of
the 1977Treaty (see paragraph 64 above); Czechoslovakia insisted on the
implementation of Variant C as a condition for further negotiation. On
26 February 1992, in a letter to his Czechoslovak counterpart, the Prime

Minister of Hungary described the impending diversion of the Danube as
"a serious breach of international law" and stated that, unless work was
suspended while further enquiries took place, "the Hungarian Govern-
ment [would] have no choice but to respond to this situation of necessity
by terminating the 1977 inter-State Treaty". In a Note Verbale dated
18March 1992,Czechoslovakia reaffirmed that, while it was prepared to

continue negotiations "on every level", it could not agree "to stop al1
work on the provisional solution".

On 24 March 1992, the Hungarian Parliament passed a resolution

authorizing the Government to terminate the 1977 Treaty if Czechoslo-
vakia did not stop the works by 30 April 1992. On 13 April 1992, the
Vice-President of the Commission of the European Communities wrote
to both parties confirming the willingness of the Commission to chair a
committee of independent experts including representatives of the two
countries, in order to assist the two ~overnments in identifying a mutu-58 GABC~KOVO-NAGYM PAOROCT (JUDGMENT)

ally acceptable solution. Commission involvement would depend on each
Government not taking "any steps . . . which would prejudice possible
actions to be undertaken on the basis of the report's findings". The

Czechoslovak Prime Minister stated in a letter to the Hungarian Prime
Minister dated 23 April 1992,that his Government continued to be inter-
ested in the establishment of the proposed committee "without any pre-
liminary conditions"; criticizing Hungary's approach, he refused to sus-
pend work on the provisional solution, but added, "in my opinion, there

is still time, until the damming of the Danube (Le., until October 31,
1992),for resolving disputed questions on the basis of agreement of both
States".

On 7 May 1992,Hungary, in the very resolution in which it decided on

the termination of the Treaty, made a proposal, this time to the Slovak
Prime Minister, for a six-month suspension of work on Variant C. The
Slovak Prime Minister replied that the Slovak Government remained
ready to negotiate, but considered preconditions "inappropriate".

91. On 19 May 1992, the Hungarian Government transmitted to the

Czechoslovak Government a Declaration notifying it of the termination
by Hungary of the 1977Treaty as of 25 May 1992. In a letter of the same
date from the Hungarian Prime Minister to the Czechoslovak Prime
Minister, the immediate cause for termination was specified to be Czecho-
slovakia'srefusal, expressed in its letter of 23 April 1992, to suspend the

work on Variant C during mediation efforts of the Commission of the
European Communities. In its Declaration, Hungary stated that it could
not accept the deleterious effects for the environment and the conserva-
tion of nature of the implementation of Variant C which would be prac-
tically equivalent to the dangers caused by the realization of the original

Project.It added that Variant C infringed numerous international agree-
ments and violated the territorial integrity of the Hungarian State by
diverting the natural course of the Danube.

92. During the proceedings, Hungary presented five arguments in sup-
port of the lawfulness, and thus the effectiveness, of its notification of
termination. These were the existence of a state of necessity; the impos-
sibility of performance of the Treaty; the occurrence of a fundamental
change of circumstances; the material breach of the Treaty by Czecho-

slovakia; and, finally, the development of new norms of international
environmental law. Slovakia contested each of these grounds.
93. On the first point, Hungary stated that, as Czechoslovakia had
"remained inflexible" and continued with its im~lementation of Variant
C, "a temporary state of necessity eventually became permanent, justify-

ing termination of the 1977 Treaty".
Slovakia, for its part, denied that a state of necessity existed on the59 GABCIKOVO-NAGYM PRR ECST(JUDGMENT)

basis of what it saw as the scientific facts; and argued that even if such a

state of necessity had existed, this would not give rise to a right to ter-
minate the Treaty under the Vienna Convention of 1969 on the Law of
Treaties.
94. Hungary's second argument relied on the terms of Article 61 of the
Vienna Convention, which is worded as follows:

"Article 61
Supervening Impossibility of'Pe~forrnunce

1. A party may invoke the impossibility of performing a treaty as
a ground for terminating or withdrawing from it if the impossibility
results from the permanent disappearance or destruction of an object

indispensable for the execution of the treaty. If the impossibility is
temporary, it may be invoked only as a ground for suspending the
operation of the treaty.
2. Impossibility of performance may not be invoked by a party as
a ground for terminating, withdrawing from or suspending the opera-

tion of a treaty if the impossibility is the result of a breach by that
party either of an obligation under the treaty or of any other inter-
national obligation owed to any other party to the treaty."

Hungary declared that it could not be "obliged to fulfil a practically
impossible task, namely to construct a barrage system on its own terri-
tory that would cause irreparable environmental damage". It concluded
that

"By May 1992 the essential object of the Treaty - an economic
joint investment which was consistent with environmental protection
and which was operated by the two parties jointly - had perma-

nently disappeared, and the Treaty had thus become impossible to
perform."
In Hungary's view, the "object indispensable for the execution of the

treaty", whose disappearance or destruction was required by Article 61 of
the Vienna Convention, did not have to be a physical object, but could
also include, in the words of the International Law Commission, "a legal
situation which was the raison d'êtreof the rights and obligations".

Slovakia claimed that Article 61 was the only basis for invoking impos-
sibility of performance as a ground for termination, that paragraph 1 of
that Article clearly contemplated physical "disappearance or destruction"
of the object in question, and that, in any event, paragraph 2 precluded
the invocation of impossibility "if the impossibility is the result of a

breach by that party . . . of an obligation under the treaty".

95. As to "fundamental change of circumstances", Hungary relied on
Article 62 of the Vienna Convention on the Law of Treaties which states

as follows: "Article 62
Fundumrntul Chunge of Circunzstances

1. A fundamental change of circumstances which has occurred
with regard to those existing at the time of the conclusion of a treaty,
and which was not foreseen by the parties, may not be invoked as a
ground for terminating or withdrawing from the treaty unless:

(a) the existence of those circumstances constituted an essential
basis of the consent of the parties to be bound by the treaty;
and
(h) the effect of the change is radically to transform the extent of

obligations still to be performed under the treaty.
2. A fundamental change of circumstances may not be invoked as
a ground for terminating or withdrawing from a treaty:

(a) if the treaty establishes a boundary; or
(h) if the fundamental change is the result of a breach by the party
invoking it either of an obligation under the treaty or of any
other international obligation owed to any other party to the
treaty.

3. If, under the foregoing paragraphs, a party may invoke a fun-
damental change of circumstances as a ground for terminating or
withdrawing from a treaty it may also invoke the change as a ground
for suspending the operation of the treaty."

Hungary identified a number of "substantive elements" present at the
conclusion of the 1977 Treaty which it said had changed fundamentally

by the date of notification of termination. These included the notion
of "socialist integration", for which the Treaty had originally been a
"vehicle", but which subsequently disappeared; the "single and indivisible
operational system", which was to be replaced by a unilateral scheme;
the fact that the basis of the planned joint investment had been over-
turned by the sudden emergence of both States into a market economy;

the attitude of Czechoslovakia which had turned the "framework treaty"
into an "immutable norm"; and, finally, the transformation of a treaty
consistent with environmental protection into "a prescription for envi-
ronmental disaster".

Slovakia, for its part, contended that the changes identified by Hun-
gary had not altered the nature of the obligations under the Treaty from
those originally undertaken, so that no entitlement to terminate it arose

from them.
96. Hungary further argued that termination of the Treaty was justi-
fied by Czechoslovakia's material breaches of the Treaty, and in this
regard it invoked Article 60 of the Vienna Convention on the Law of
Treaties, which provides: GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

"Article 60
Terminution or Suspension of the Operution ofu Treaty
us u Consequence of ItsBreach

1.A material breach of a bilateral treaty by one of the parties
entitles the other to invoke the breach as a ground for terminating
the treaty or suspending its operation in whole or in part.

2. A material breach of a multilateral treaty by one of the parties

entitles:
(a) the other parties by unanimous agreement to suspend the opera-
tion of the treaty in whole or in part or to terminate it either:

(i) in the relations between themselves and the defaulting State,
or
(ii) as between al1the parties;

(b) a party specially affected by the breach to invoke it as a ground
for suspending the operation of the treaty in whole or in part in
the relations between itself and the defaulting State;

(c) any party other than the defaulting State to invoke the breach
as a ground for suspending the operation of the treaty in whole

or in part with respect to itself if the treaty is of such a charac-
ter that a material breach of its provisions by one party radi-
cally changes the position of every party with respect to the
further performance of its obligations under the treaty.

3. A niaterial breach of a treaty, for the purposes of this article,
consists in:
(a) a repudiation of the treaty not sanctioned by the present Con-
vention; or

(6) the violation of a provision essential to the accomplishment of
the object or purpose of the treaty.
4. The foregoing paragraphs are without prejudice to any provi-
sion in the treaty applicable in the event of a breach.

5. Paragraphs 1 to 3 do not apply to provisions relating to the
protection of the human person contained in treaties of a humani-
tarian character, in particular to provisions prohibiting any form of
reprisals against perçons protected by such treaties."

Hungary claimed in particular that Czechoslovakia violated the 1977
Treaty by proceeding to the construction and putting into operation of
Variant C, as well as failing to comply with its obligations under Ar-
ticles 15 and 19 of the Treaty. Hungary further maintained that Czecho-

slovakia had breached other international conventions (among them the
Convention of 31 May 1976 on the Regulation of Water Management
Issues of Boundary Waters) and general international law.62 GABC~KOVO-NAGYM PAOROCT (JUDGMENT)

Slovakia denied that there had been, on the part of Czechoslovakia or
on its part, any material breach of the obligations to protect water qual-
ity and nature, and claimed that Variant C, far from being a breach, was
devised as "the best possible approximate application" of the Treaty. It

furthermore denied that Czechoslovakia had acted in breach of other
international conventions or general international law.

97. Finally, Hungary argued that subsequently imposed requirements
of international law in relation to the protection of the environment pre-

cluded performance of the Treaty. The previously existing obligation not
to cause substantive damage to the territory of another State had, Hun-
gary claimed, evolved into an ergu omnes obligation of prevention of
damage pursuant to the "precautionary principle". On this basis, Hun-
gary argued, its termination was "forced by the other party's refusal to
suspend work on Variant Cm.

Slovakia argued, in reply, that none of the intervening developments in
environmental law gave rise to norms of juscogens that would override
the Treaty. Further, it contended that the claim by Hungary to be
entitled to take action could not in any event serve as legal justification

for termination of the Treaty under the law of treaties, but belonged
rather "to the language of self-help or reprisals".

98. The question, as formulated in Article 2, paragraph 1 (c),of the
Special Agreement, deals with treaty law since the Court is asked to
determine what the legal effects are of the notification of termination of
the Treaty. The question is whether Hungary's notification of 19 May
1992 brought the 1977 Treaty to an end, or whether itdid not meet the

requirements of international law, with the consequence that it did not
terminate the Treaty.
99. The Court has referred earlier to the question of the applicability
to the present case of the Vienna Convention of 1969on the Law of Trea-
ties. The Vienna Convention is not directly applicable to the 1977Treaty

inasmuch as both States ratified that Convention only after the Treaty's
conclusion. Consequently only those rules which are declaratory of cus-
tomary law are applicable to the 1977 Treaty. As the Court has already
stated above (see paragraph 46), this is the case, in many respects, with
Articles 60 to 62 of the Vienna Convention. relatine "o termination or
suspension of the operation of a treaty. On this, the Parties, too, were

broadly in agreement.
100. The 1977Treaty does not contain any provision regarding its ter-
mination. Nor is there any indication that the parties intended to admit
the possibility of denunciation or withdrawal. On the contrary, the
Treaty establishes a long-standing and durable régimeof joint investment63 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

and joint operation. Consequently, the parties not having agreed other-
wise, the Treaty could be terminated only on the limited grounds enu-

merated in the Vienna Convention.

101. The Court will now turn to the first ground advanced by Hun-

gary, that of the state of necessity. In this respect, the Court will merely
observe that, even if a state of necessity is found to exist, it is not a
ground for the termination of a treaty. It may only be invoked to exon-
erate from its responsibility a State which has failed to implement a
treaty. Even if found justified, it does not terminate a Treaty; the Treaty

may be ineffective as long as the condition of necessity continues to exist;
it may in fact be dormant, but - unless the parties by mutual agreement
terminate the Treaty - it continues to exist. As soon as the state of
necessity ceases to exist, the duty to comply with treaty obligations

revives.

102. Hungary also relied on the principle of the impossibility of per-

formance as reflected in Article 61 of the Vienna Convention on the Law
of Treaties. Hungary's interpretation of the wording of Article 61 is,
however, not in conformity with the terms of that Article, nor with the
intentions of the Diplomatic Conference which adopted the Convention.

Article 6 1, paragraph 1, requires the "permanent disappearance or
destruction of an object indispensable for the execution" of the treaty to
justify the termination of a treaty on grounds of impossibility of perform-
ance. During the conference, a proposal was made to extend the scope of
the article by including in it cases such as the impossibility to make cer-

tain payments because of serious financial difficulties (Ojjciul Records of
the United Nations Conjerence on the Luiv qf' Treuties, First Session,
Vienna, 26 Murch-24 Muy 1968, doc. A/CONF.39/11, Summary records
of the plenary meetings and of the meetings of the Committee of the
Whole, 62nd Meeting of the Committee of the Whole, pp. 361-365).

Although it was recognized that such situations could lead to a preclu-
sion of the wrongfulness of non-performance by a party of its treaty
obligations, the participating States were not prepared to consider such
situations to be a ground for terminating or suspending a treaty,

and preferred to limit themselves to a narrower concept.
103. Hungary contended that the essential object of the Treaty - an
economic joint investment which was consistent with environmental pro-
tection and which was operated by the two contracting parties jointly -
had permanently disappeared and that the Treaty had thus become

impossible to perform. It is not necessary for the Court to determine
whether the term "object" in Article 61 can also be understood to
embrace a legal régime as in any event, even if that were the case, itwould have to conclude that in this instance that régimehad not defini-
tively ceased to exist. The 1977Treaty - and in particular its Articles 15,
19 and 20 - actually made available to the parties the necessary means
to proceed at any time, by negotiation, to the required readjustments

between economic imperatives and ecological imperatives. The Court
would add that, if the joint exploitation of the investment was no longer
possible, this was originally because Hungary did not carry out most of
the works for which it was responsible under the 1977Treaty; Article 61,
paragraph 2, of the Vienna Convention expressly provides that impossi-
bility of performance may not be invoked for the termination of a treaty

by a party to that treaty when it results from that party's own breach of
an obligation flowing from that treaty.

104. Hungary further argued that it was entitled to invoke a number
of events which, cumulatively, would have constituted a fundamental
change of circumstances. In this respect it specified profound changes of

a political nature, the Project's diminishing economic viability, the
progress of environmental knowledge and the development of new norms
and prescriptions of international environmental law (see paragraph 95
above).

The Court recalls that, in the Fislzrries Jurisdiction case, it stated that

"Article 62 of the Vienna Convention on the Law of Treaties, . ..
may in many respects be considered as a codification of existing cus-
tomary law on the subject of the termination of a treaty relationship
on account of change of circumstances" (I.C.J. Reports 1973, p. 63,
para. 36).

The prevailing political situation was certainly relevant for the conclu-

sion of the 1977Treaty. But the Court will recall that the Treaty provided
for a joint investment programme for the production of energy, the con-
trol of floods and the improvement of navigation on the Danube. In the
Court's view, the prevalent political conditions were thus not so closely
linked to the object and purpose of the Treaty that they constituted an
essential basis of the consent of the parties and, in changing, radically

altered the extent of the obligations still to be performed. The same holds
good for the economic system in force at the time of the conclusion of the
1977 Treaty. Besides, even though the estimated profitability of the
Project might have appeared less in 1992than in 1977, it does not appear
from the record before the Court that it was bound to diminish to such
an extent that the treaty obligations of the parties would have been radi-
cally transformed as a result.

The Court does not consider that new developments in the state ofenvironmental knowledge and of environmental law can be said to
have been completely unforeseen. What is more, the formulation of
Articles 15, 19 and 20, designed to accommodate change, made it pos-
sible for the parties to take account of such developments and to apply

them when implementing those treaty provisions.
The changed circumstances advanced by Hungary are, in the Court's
view, not of such a nature, either individually or collectively, that their
effect would radically transform the extent of the obligations still to be
performed in order to accomplish the Project. A fundamental change of
circumstances must have been unforeseen; the existence of the circum-

stances at the time of the Treaty's conclusion must have constituted an
essential basis of the consent of the parties to be bound by the Treaty.
The negative and conditional wording of Article 62 of the Vienna Con-
vention on the Law of Treaties is a clear indication moreover that the
stability of treaty relations requires that the plea of fundamental change
of circumstances be applied only in exceptional cases.

105. The Court will now examine Hungary's argument that it was
entitled to terminate the 1977Treaty on the ground that Czechoslovakia

had violated its Articles 15, 19and 20 (as well as a number of other con-
ventions and rules of general international law); and that the planning,
construction and putting into operatinn of Variant C also amounted to a
material breach of the 1977 Treatv.
106. As to that part of Hungary's argument which was based on other
treaties and general rules of international law, the Court is of the view

that it is only a material breach of the treaty itself, by a State party to
that treaty, which entitles the other party to rely on it as a ground for
terminating the treaty. The violation of other treaty rules or of rules of
general international law may justify the taking of certain measures,
including countermeasures, by the injured State, but it does not consti-
tute a ground for termination under the law of treaties.

107. Hungary contended that Czechoslovakia had violated Articles 15,
19 and 20 of the Treaty by refusing to enter into negotiations with Hun-
gary in order to adapt the Joint Contractual Plan to new scientific and
legal developments regarding the environment. Articles 15, 19 and 20
oblige the parties jointly to take, on a continuous basis, appropriate

measures necessary for the protection of water quality, of nature and of
fishing interests.

Articles 15 and 19 expressly provide that the obligations they contain
shall be implemented by the means specified in the Joint Contractual
Plan. The failure of the parties to agree on those means cannot, on the

basis of the record before the Court, be attributed solely to one party.66 GABC~KOVO-NAGYM PAOROCT (JUDGMENT)

The Court has not found sufficient evidence toconclude that Czechoslo-
vakia had consistently refused to consult with Hungary about the desir-
ability or necessity of measures for the preservation of the environment.
The record rather shows that, while both parties indicated, in principle, a
willingness to undertake further studies, in practice Czechoslovakia
refused to countenance a suspension of the works at Dunakiliti and,

later, on VariantC, while Hungary required suspension as a prior condi-
tion of environmental investigation because it claimed continuation of
the work would prejudice the outcome of negotiations. In this regard it
cannot be left out of consideration that Hungaryitself, by suspending the
works at Nagymaros and Dunakiliti, contributed to the creation of a
situation which was not conducive to the conduct of fruitful negotiations.

108. Hungary's main argument for invoking a material breach of the
Treaty was the construction and putting into operation of Variant C. As

the Court has found in paragraph 79 above, Czechoslovakia violated the
Treaty only when it diverted the waters of the Danube into the bypass
canal in October 1992. In constructing the works which would lead to
the putting into operation of Variant C, Czechoslovakia did not act
unlawfully.
In the Court's view, therefore, the notification of termination by Hun-

gary on 19 May 1992 was premature. No breach of the Treaty by
Czechoslovakia had yet taken place and consequently Hungary was not
entitled to invoke any such breach of the Treaty as a ground for termi-
nating it when it did.
-109. In this regard, it should be noted that, according to Hungary's
Declaration of 19 May 1992, the termination of the 1977 Treaty was to

take effect as from 25 May 1992, that is only six days later. Both Parties
agree that Articles65 to 67 of the Vienna Convention on the Law of
Treaties, if not codifying customary law, at least generally reflect custom-
ary international law and contain certain procedural principles which are
based on an obligation to act in good faith. As the Court stated in its
Advisory Opinion on the Interpretufion of tlze Agreement of 25 March

1951 hetiilren tlze WHO und Egypt (in which case the Vienna Convention
did not apply) :

"Precisely what periods of time may be involved in the observance
of the duties to consult and negotiate, and what period of notice of
termination should be given, are matters which necessarily Vary
according to the requirements of the particular case. In principle,
therefore, it is for the parties in each case to determine the length of

those periods by consultation and negotiation in good faith." C.J.
Reports 1980, p. 96, para. 49.)
The termination of the Treaty by Hungary was to take effect six days67 GABCIKOVO-NAGYM PRORECT (JUDGMENT)

after its notification. On neither of these dates had Hungary suffered

injury resulting from acts of Czechoslovakia. The Court must therefore
confirm its conclusion that Hungary's termination of the Treaty was
premature.
110. Nor can the Court overlook that Czechoslovakia committed the
internationally wrongful act of putting into operation Variant C as a
result of Hungary's own prior wrongful conduct. As was stated by the

Permanent Court of International Justice:

"It is, moreover, a principle generally accepted in the jurispru-
dence of international arbitration,as well as by municipal courts,
that one Party cannot avail himself of the fact that the other has not
fulfilled some obligation or has not had recourse to some means of
redress, if the former Party has, by some illegal act, prevented the

latter from fulfilling the obligation in question, or from having
recourse to the tribunal which would have been open to him." (Fuc-
tory at Chorzo~v, Jurisdiction, Juclgment No. 8, 1927, P.C.IJ..
Series A, No. 9, p.31.)

Hungary, by its own conduct, had prejudiced its right to terminate the
Treaty; this would still have been the case even if Czechoslovakia, by the
time of the purported termination, had violated a provision essential to

the accomplishment of the object or purpose of the Treaty.

111. Finally,the Court will address Hungary's claim that it was
entitled to terminate the 1977 Treaty because new requirements of inter-
national law for the protection of the environment precluded perfor-

mance of the Treaty.
112. Neither of the Parties contended that new DeremDtorv norms of
environmental law had emerged since the conclusion of tke 1677Treaty,
and the Court will consequently not be required to examine the scope of
Article64 of the Vienna Convention on the Law of Treaties. On the other
hand, the Court wishes to point out that newly developed norms of envi-

ronmental law are relevant for the implementation of the Treaty and that
the parties could, by agreement, incorporate them through the applica-
tion of Articles 15, 19and 20 of the Treaty. These articles do not contain
specific obligations of performance but require the parties, in carrying
out their obligations to ensure that the quality of water in the Danube is
not impaired and that nature is protected, to take new environmental

norms into consideration when agreeing upon the means to be specified
in the Joint Contractual Plan.

By inserting these evolving provisions in the Treaty, the parties recog-
nized the potential necessity to adapt the Project. Consequently, the68 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

Treaty is not static, and is open to adapt to emerging norms of interna-
tional law. By means of Articles 15and 19,new environmental norms can

be incorporated in the Joint Contractual Plan.

The responsibility to do this was a joint responsibility. The obligations
contained in Articles 15, 19and 20 are, by definition, general and have to
be transformed into specific obligations of performance through a pro-
cess of consultation and negotiation. Their implementation thus requires

a mutual willingness to discuss in good faith actual and potential environ-
mental risks.
It isl1the more important to do this because as the Court recalled in
its Advisory Opinion on the Legulity of the Threut or Use of Nucleur
Weupons, "the environment is not an abstraction but represents the living
space, the quality of life and the very health of human beings, including

generations unborn" (I. C.J. Reports 1996, p. 241, para. 29; see also para-
graph 53 above).
The awareness of the vulnerability of the environment and the recogni-
tion that environmental risks haveto be assessed on a continuous basis
have become much stronger in the years since the Treaty's conclusion.
These new concerns have enhanced the relevance of Articles 15, 19
and 20.

113. The Court recognizes that both Parties agree on the need to take
environmental concerns seriously and to take the required precautionary
measures, but they fundamentally disagree on the consequences this has
for the joint Project. In such a case, third-party involvement may be help-
ful and instrumental in finding a solution, provided each of the Parties is
flexible in its position.

114. Finally, Hungary maintained that by their conduct both parties
had repudiated the Treaty and that a bilateral treaty repudiated by both
parties cannot survive. The Court is of the view, however, that although
it has found that both Hungary and Czechoslovakia failed to comply
with their obligations under the 1977 Treaty, this reciprocal wrongful

conduct did not bring the Treaty to an end nor justify its termination.
The Court would set a precedent with disturbing implications for treaty
relations and the integrity of the rule puctu sunt servunda if it were to
conclude that a treaty in force between States, which the parties have
implemented in considerable measure and at great cost over a period of
years, might be unilaterally set aside on grounds of reciprocal non-

compliance. It would be otherwise, of course, if the parties decided to
terminate the Treaty by mutual consent. But in this case, while Hungary
purported to terminate the Treaty, Czechoslovakia consistently resisted
this act and declared it to be without legal effect. 115. In the light of the conclusions it has reached above, the Court, in
reply to the question put to it in Article 2, paragraph 1 (c), of the Special

Agreement (see paragraph 89), finds that the notification of termination
by Hungary of 19 May 1992 did not have the legal effect of terminating
the 1977 Treaty and related instruments.

116. In Article 2,paragraph 2, of the Special Agreement, the Court is

requested to determine the legal consequences, including the rights and
obligations for the Parties, arising from its Judgment on the questions
formulated in paragraph 1. In Article 5 of the Special Agreement the
Parties agreed to enter into negotiations on the modalities for the execu-
tion of the Judgment immediately after the Court has rendered it.
117. The Court must first turn to the question whether Slovakia

became a party to the 1977Treaty as successoi to Czechoslovakia. As an
alternative argument, Hungary contended that, even if the Treaty sur-
vived the notification of termination, in any event it ceased to be in force
as a treaty on 31 December 1992,as a result of the "disappearance of one
of the parties". On that date Czechoslovakia ceased to exist as a legal
entity, and on 1 January 1993the Czech Republic and the Slovak Repub-

lic came into existence.

118. According to Hungary, "There is no rule of international law
which provides for automatic succession to bilateral treaties on the dis-
appearance of a party" and such a treaty will not survive unless another
State succeeds to it by express agreement between that State and the

remaining party. While the second paragraph of the Preamble to the
Special Agreement recites that

"the Slovak Republic is one of the two successor States of the Czech
and Slovak Federal Republic and the sole successor State in respect
of rights and obligations relating to the Gabtikovo-Nagymaros
Project",

Hungary sought to distinguish between, on the one hand, rights and obli-
gations such as "continuing property rights" under the 1977Treaty, and,
on the other hand, the treaty itself. It argued that, during the negotiations
leading to signature of the Special Agreement, Slovakia had proposed a

text in which it would have been expressly recognized "as the successor to
the Government of the CSFR" with regard to the 1977 Treaty, but that
Hungary had rejected that formulation. It contended that it had never
agreed to accept Slovakia as successor to the 1977 Treaty. Hungary
referred to diplomatic exchanges in which the two Parties had each sub-
mitted to the other lists of those bilateral treaties which they respectively

wished should continue in force between them. for negotiation on a case-70 GABCIKOVO-NAGYM ARROEST (JUDGMENT)

by-case basis; and Hungary emphasized that no agreement was ever

reached with regard to the 1977 Treaty.

119. Hungary claimed that tbere was no rule of succession which
could operate in the present case to override the absence of consent.
Referring to Article 34 of the Vienna Convention of 23August 1978on

Succession of States in respect of Treaties, in which "a rule of automatic
succession to al1treaties is provided for", based on the principle of con-
tinuity, Hungary argued not only that it never signed or ratified the Con-
vention, but that the "concept of automatic succession" contained in that
Article was not and is not, and has never been accepted as, a statement of

general international 1aw.

Hungary further submitted that the 1977 Treaty did not create "obli-
gations and rights . . . relating to the régimeof a boundary" within the
meaning of Article II of that Convention, and noted that the existing
course of the boundary was unaffected by the Treaty. It also denied that

the Treaty was a "localized" treaty, or that it created rights "considered
as attaching to [the] territory" within the meaning of Article 12 of the
1978 Convention, which would, as such, be unaffected by a succession of
States. The 1977Treaty was, Hungary insisted, simply a joint investment.
Hungary's conclusion was that there is no basis on which the Treaty

could have survived the disappearance of Czechoslovakia so as to be
binding as between itself and Slovakia.

120. According to Slovakia, the 1977 Treaty, which was not lawfully
terminated by Hungary's notification in May 1992, remains in force

between itself, as successor State, and Hungary.
Slovakia acknowledged that there was no agreement on succession to
the Treaty between itself and Hungary. It relied instead, in the first place,
on the "general rule of continuity which applies in the case of dissolu-
tion"; it argued, secondly, that the Treaty is one "attaching to [the] ter-
ritory" within the meaning of Article 12of the 1978 Vienna Convention,

and that it contains provisions relating to a boundary.
121. In support of its first argument Slovakia cited Article 34 of the
1978 Vienna Convention, which it claimed is a statement of customary
international law, and which imposes the principle of automatic succes-
sion as the rule applicable in the case of dissolution of a State where the

~redecessor State has ceased to exist. Slovakia maintained that State
practice in cases of dissolution tends to support continuity as thele to
be followed with regard to bilateral treaties. Slovakia havingsucceeded
to part of the territory of the former Czechoslovakia, this would be the
rule applicable in the present case.
122. Slovakia's second argument rests on "the principle of ipso jure

continuity of treaties of a territorial or localized character". This rule,
Slovakia said, is embodied in Article 12of the 1978Convention, which in
part provides as follows:71 GABCIKOVO-NAGYM PRR ECST(JUDGMENT)

"Article 12

Other Territorial Regimes
........................

2. A succession of States does not as such affect:
(a) obligations relating to the use of any territory, orto restrictions
upon its use, established by a treaty for the benefit of a group of

States or of al1States and considered as attaching to that terri-
tory;
(h) rights established by a treaty for the benefit of a group of States
or of al1 States and relating to the use of any territory, or to
restrictions upon its use, and considered as attaching to that
territory."

According to Slovakia, "[this] article [too] can be considered to be one
of those provisions of the Vienna Convention that represent the codifica-
tion of customary international law". The 1977 Treaty is said to fall

within its scoDe because of its "suecific characteristics . . . which ulace it
in the category of treaties of a localized or territorial character". Slovakia
also described the Treaty as one "which contains boundary provisions
and lays down a specific territorial régime" whichoperates in the interest
of al1Danube riparian States, and as "a dispositive treaty, creating rights
in rem, independently of the legal personality of its original signatories".

Here, Slovakia relied on the recognition by the International Law Com-
mission of the existence of a "special rule" whereby treaties "intended to
establish an objective régime" must be considered as binding on a suc-
cessor State (OfJicial Records of the United Nations Conferencc on the
Succession ofStutes in respect of Treaties, Vol.III,doc. AICONF.80I16I
Add.2, p. 34). Thus, in Slovakia's view, the 1977 Treaty was not one

which could have been terminated through the disappearance of one of
the original parties.

123. The Court does not find it necessary for the purposes of the
present case to enter into a discussion of whether or not Articl34 of the

1978 Convention reflects the state of customary international law. More
relevant to its present analysis is the particular nature and character of
the 1977Treaty. An examination of this Treaty confirms that, aside from
its undoubted nature as a joint investment, its major elements were the
proposed construction and joint operation of a large, integrated and indi-
visible complex of structures and installations on specific parts of the

respective territories of Hungary and Czechoslovakia along the Danube.
The Treaty also established the navigational régimefor an important sec-
tor of an international waterway, in particular the relocation of the main
international shipping lane to the bypass canal. In so doing, it inescap-
ably created a situation in which the interests of other users of the Dan-72 GABCIKOVO-NAGYM PAOJOCT (JUDGMENT)

ube wereaffected. Furthermore, the interests of third States were expressly
acknowledged in Article 18, whereby the parties undertook to ensure
"uninterrupted and safe navigation on the international fairway" in
accordance with their obligations under the Convention of 18 August
1948concerning the Régimeof Navigation on the Danube.

In its Commentary on the Draft Articles on Succession of States in
respect of Treaties, adopted at itswenty-sixth session, the International
Law Commission identified "treaties of a territorial character" as having
been regarded both in traditional doctrine and in modern opinion as un-
affected by a succession of State(OfJicial Records of the United Nations

Conference on the Succession of States in respect of Treaties, Vol. III,
doc. A/CONF.80/16/Add.2, p. 27, para. 2). The draft text of Article 12,
which reflects this principle, was subsequently adopted unchanged in the
1978Vienna Convention. The Court considers that Article 12 reflects a
rule of customary international law; it notes that neither of the Parties
disputed this. Moreover, the Commission indicated that "treaties con-
cerning water rights or navigation on rivers are commonly regarded as
candidates for inclusion in the category of territorial treaties" (ibid.,
p. 33, para. 26). The Court observes that Article 12, in providing only,
without reference to the treaty itself, that rights and obligations of a ter-
ritorial character established by a treaty are unaffected by a succession of
States, appears to lend support to the position of Hungary ratherthan of
Slovakia. However the Court concludes that this formulation was devised

rather to take account of the fact that, in many cases, treaties which had
established boundaries or territorial régimes wereno longer in force
(ibid,pp. 26-37). Those that remained in force would nonetheless bind a
successor State.

Taking al1these factors into account, the Court finds that the content
of the 1977 Treaty indicates that it must be regarded as establishing a
territorial régimewithin the meaning of Article 12 of the 1978 Vienna
Convention. It created rights and obligations "attaching tomthe parts of
the Danube to which it relates; thus the Treaty itself cannot be affected
by a succession of States. The Court therefore concludes that the 1977
Treaty became binding upon Slovakia on 1 January 1993.
124. It might be added that Slovakia also contended that, while still a
constituent part of Czechoslovakia, it played aole in the development of

the Project, as it did later, in the most critical phase of negotiations with
Hungary about the fate of the Project. The evidence shows that the Slo-
vak Government passed resolutions prior to the signing of the 1977
Treaty in preparation for its implementation; and again, after signature,
expressing its support for the Treaty. It was the Slovak Prime Minister
who attended the meeting held in Budapest on 22 April 1991as the Pleni-
potentiary of the Federal Government to discuss questions arising out of
the Project.Itwas his successor as Prime Minister who notified his Hun-73 GABCIKOVO-NAGYM PROJES T(JL'DC~MENT)

garian counterpart by letter on 30 July 1991 of the decision of the Gov-
ernment of the Slovak Republic, as well as of the Government of the
Czech and Slovak Federal Republic, to proceed with the "provisional
solution" (see paragraph 63 above); and who wrote again on 18 Decem-
ber 1991 to the Hungarian Minister without Portfolio, renewing an

earlier suggestion that a joint commission be set up under the auspices of
the European Communities to consider possible solutions. The Slovak
Prime Minister also wrote to the Hungarian Prime Minister in May 1992
on the subject of the decision taken by the Hungarian Government to
terminate the Treaty, informing him of resolutions passed by the Slovak
Government in response.

It is not necessary, in the light of the conclusions reached in para-
graph 123above, for the Court to determine whether there are legal con-
sequences to be drawn from the prominent part thus played by the Slo-
vak Republic. Its role does, however, deserve mention.

125. TheCourt now turns to the other legal consequences arising from
its Judgment.
As to this, Hungary argued that future relations between the Parties, as
far as Variant C is concerned, are not governed by the 1977 Treaty. It
claims that it is entitled, pursuant to the Convention of 1976 on the
Regulation of Water Management Issues of Boundary Waters, to "50%

of the natural flow of the Danube at the point at which it crosses the
boundary below ~unovo" and considers that the Parties
"are obliged to enter into negotiations in order to produce the result

that the water conditions along the area from below Cunovo to
below the confluence at Sap becomejointly defined water conditions
as required by Article 3 (u) of the 1976 Convention".

Hungary moreover indicated that any mutually accepted long-term dis-
charge régimemust be "capable of avoiding damage, including especially
damage to biodiversity prohibited by the [1992 Rio Convention on Bio-
logical Diversity]". It added that "a joint environmental impact assess-

ment of the region and of the future of Variant C structures in the con-
text of the sustainable development of the region" should be carried out.

126. Hungary also raised the question of financial accountability for
the failure of the original project and stated that both Parties accept the
fact that the other has "proprietary and financial interests in the residues

of the original Project and that an accounting has to be carried out".
Furthermore, it noted that:
"Other elements of damage associated with Variant C on Hungar-

ian territory also have to be brought into the accounti...,as well
as electricity production since the diversion",74 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

and that: "The overall situation is a complex one, and it may be most
easily resolved by some form of lump sum settlement."

127. Hungary stated that Slovakia had incurred international respon-
sibility and should make reparation for the damage caused to Hungary
by the operation of Variant C. In that connection, it referred, in the con-
text of reparation of the damage to the environment, to the rule of res-
titutio in integrum, and called for the re-establishment of "joint control

by the two States over the installations maintained as they are now", and
the "re-establishment of the flow of [the] waters to the level at which it
stood prior to the unlawful diversion of the river". It also referred to
reparation of the damage to the fauna, the flora, the soil, the sub-soil, the
groundwater and the aquifer, the damages suffered by the Hungarian

population on account of the increase in the uncertainties weighing on its
future (pretium doloris), and the damage arising from the unlawful use,
in order to divert the Danube, of installations over which the two Parties
exercised joint ownership.
Lastly, Hungary called for the "cessation of the continuous unlawful
acts" and a "guarantee that the same actions will not be repeated", and

asked the Court to order "the permanent suspension of the operation of
Variant Cm.
128. Slovakia argued for its part that Hungary should put an end to its
unlawful conduct and cease to impede the application of the 1977Treaty,
taking account of its "flexibility and of the important possibilities of

development for which it provides, or even of such amendments as might
be made to it by agreement between the Parties, further to future nego-
tiations". It stated that joint operations could resume on a basis jointly
agreed upon and emphasized the following:

"whether Nagymaros is built as originally planned, or built else-
where in a different form, or, indeed, not built at all, is a question to

be decided by the Parties some time in the future.

Provided the bypass canal and the Gabtikovo Power-station and
Locks - both part of the original Treaty, and not part of Variant C
- remain operational and economically viable and efficient, Slo-

vakia is prepared to negotiate over the future roles of Dunakiliti
and Cunovo, bearing Nagymaros in mind."

It indicated that the Gabtikovo power plant would not operate in peak
mode "if the evidence of environmental damage [was]clear and accepted
by both Parties". Slovakia noted that the Parties appeared to agree that

an accounting should be undertaken "so that, guided by the Court's find-
ings on responsibility, the Parties can try to reach a global settlement". Itadded that the Parties would have to agree on how the sums due are to be
paid.

129. Slovakia stated that Hungary must make reparation for the
deleterious consequences of its failures to comply with its obligations,
"whether they relate to its unlawful suspensions and abandonments of
works or to its formal repudiation of the Treaty as from May 1992", and

that compensation should take the form of a rrstitutio in integrum. It
indicated that "Unless the Parties come to some other arrangement by
concluding an agreement, restitutio in integrurn ought to take the form of
a return by Hungary, ut a future tirne, to its obligations under the
Treaty" and that "For compensation to be 'full' . . ., to 'wipe out al1the
consequences of the illegal act' . .,a payment of compensation must . . .

be added to the rcstitutio .." Slovakia claims compensation which must
include both interest and loss of profits and should cover the following
heads of damage, which it offers by way of guidance:

(1) Losses caused to Slovakia in the GabCikovo sector: costs incurred
from 1990 to 1992 by Czechoslovakia in protecting the structures of
the GIN project and adjacent areas; the cost of maintaining the old
bed of the River Danube pending the availability of the new naviga-
tion canal, from 1990to 1992; losses to the Czechoslovak navigation
authorities due to the unavailability of the bypass canal from 1990to
1992 ; construction costs of Variant C (1990-1992).

(2) Losses caused to Slovakia in the Nagymaros sector: losses in the field
of navigation and flood protection incurred since 1992 by Slovakia
due to the failure of Hungary to proceed with the works.

(3) Loss of electricity production.

Slovakia also calls for Hungary to "give the appropriate guarantees
that it will abstain from preventing the application of the Treaty and the
continuous operation of the system". It argued from that standpoint that
it is entitled "to be given a formal assurance that the internationally

wrongful acts of Hungary will not recur':, and it added that "the main-
tenance of the closure of the Danube at Cunovo constitutes a guarantee
of that kind", unless Hungary gives an equivalent guarantee "within the
frameworkof the negotiations that are to take place between the Parties".

130. The Court observes that the part of its Judgment which answers
the questions in Article 2, paragraph 1, of the Special Agreement has a
declaratory character. 1t deals with the past conduct of the Parties and
determines the lawfulness or unlawfulness of that conduct between 1989
and 1992 as well as its effects on the existence of the Treaty.
131. Now the Court has, on the basis of the foregoing findings, to76 GABCIKOVO-NAGYM PROROEST (JUDGMENT)

determine what the future conduct of the Parties should be. This part of
the Judgment is prescriptive rather than declaratory because it deter-

mines what the rights and obligations of the Parties are. The Parties will
have to seek agreement on the modalities of the execution of the Judg-
ment in the light of this determination, as they agreed to do in Article 5
of the Special Agreement.

132. In this regard it is of cardinal importance that the Court has
found that the 1977 Treaty is still in force and consequently governs the
relationship between the Parties. That relationship is also determined by

the rules of other relevant conventions to which the two States are party,
by the rules of general international law and, in this particular case, by
the rules of State responsibility; but it is governed, above all, by the
applicable rules of the 1977 Treaty as a les speciulis.
133. The Court, however, cannot disregard the fact that theTreaty has

not been fully implemented by either party for years, and indeed that
their acts of commission and omission have contributed to creating the
factual situation that now exists. Nor can it overlook that factual situa-
tion - or the practical possibilities and impossibilities to which it gives
rise- when deciding on the legal requirements for the future conduct of

the Parties.
This does not mean that facts - in this case facts which flow from
wrongful conduct - determine the law. The principle e.u injuriajus non
oritur is sustained by the Court's finding that the legal relationship

created by the 1977Treaty is preserved and cannot in this case be treated
as voided by unlawful conduct.
What is essential, therefore, is that the factual situation as it has devel-
oped since 1989 shall be placed within the context of the preserved and
developing treaty relationship, in order to achieve its object and purpose

in so far as that is feasible. For it is only then that the irregular state of
affairs which exists as the result of the failure of both Parties to comply
with their treaty obligations can be remedied.
134. What might have been a correct application of the law in 1989or

1992, if the case had been before the Court then, could be a miscarriage
ofjustice if prescribed in 1997.The Court cannot ignore the fact that the
GabEikovo power plant has bpen in operation for nearly five years, that
the bypass canal which feeds the plant receives its water from a signifi-
cantly smaller reservoir formed by a dam which is built not at Dunakiliti

but at Cunovo, and that the plant is operated in a run-of-the-river mode
and not in a peak hour mode as originally foreseen. Equally, the Court
cannot ignore the fact that, not only has Nagymaros not been built, but
that, with the effective discarding by both Parties of peak power opera-
tion, there is no longer any point in building it.

135. As the Court has already had occasion to point out, the 1977
Treaty was not only a joint investment project for the production of77 GABC~KOVO-NAGYM PAOJOCT (JUDGMENT)

energy, but it was designed to serve other objectives asell: the improve-
ment of the navigability of the Danube, flood control and regulation of

ice-discharge, and the protection of the natural environment. None of
these objectives has been given absolute priority over the other, in spite
of the emphasis which is given in the Treaty to the construction of a
System of Locks for the production of energy. None of them has lost its
importance. In order to achieve these objectives the parties accepted obli-

gations of conduct, obligations of performance, and obligations of result.

136. It could be said that that part of the obligations of performance
which related to the construction of the System of Locks - in so far as

they were not yet implemented before 1992 - have been overtaken by
events. It would be an administration of the law altogether out of touch
with reality if the Court were to order those obligations to be fully re-
instated and the works at Cunovo to be demolished when the objectives
of the Treaty can be adequately served by the existing structures.

137. Whether this is indeed the case is, first and foremost, for the
Parties to decide. Under the 1977 Treaty ils several objectives must be
attained in an integrated and consolidated programme, to be developed
in the Joint Contractual Plan. The Joint Contractual Plan was, until

1989, adapted and amended frequently to better fit the wishes of the
parties. This Plan was also expressly described as the means to achieve
the objectives of maintenance of water quality and protection of the envi-
ronment.
138. The 1977 Treaty never laid down a rigid system, albeit that the

construction of a system of locks at GabEikovo and Nagymaros was pre-
scribed by the Treaty itself. In this respect, however, the subsequent posi-
tions adopted by the parties should be taken into consideration. Not only
did Hungary insist on terminating construction at Nagymaros, but

Czechoslovakia stated, on various occasions in the course of negotia-
tions, that it was willing to consider a limitation or even exclusion of
operation in peak hour mode. In the latter case the construction of the
Nagymaros dam would have become pointless. The explicit terms of the
Treaty itself were therefore in practice acknowledged by the parties to be

negotiable.
139. The Court is of the opinion that the Parties are under a legal obli-
gation, during the negotiations to be held by virtue of Article 5 of the
Special Agreement, to consider, within the context of the 1977Treaty, in
what way the multiple objectives of the Treaty can best be served, keep-

ing in mind that al1of them should be fulfilled.
140. It is clear that the Project's impact upon, and its implications for,
the environment are of necessity a key issue. The numerous scientific
reports which have been presented to the Court by the Parties - even if

their conclusions are often contradictory - provide abundant evidence
that this impact and these implications are considerable.
In order to evaluate the environmental risks, current standards must be
taken into consideration. This is not only allowed by the wording ofArticles 15 and 19, but even prescribed, to the extent that these
articles impose a continuing - and thus necessarily evolving - obliga-
tion on the parties to maintain the quality of the water of the Danube

and to protect nature.
The Court is mindful that, in the field of environmental protection,
vigilance and prevention are required on account of the often irreversible
character of damage to the environment and of the limitations inherent
in the very mechanism of reparation of this type of damage.

Throughout the ages, mankind has, for economic and other reasons,
constantly interfered with nature. In the past, this was often done with-
out consideration of the effects upon the environment. Owing to new
scieritificinsights and to a growing awareness of the risks for mankind -

for present and future generations - of pursuit of such interventions at
an unconsidered and unabated pace, new norms and standards have been
developed, set forth in a great number of instruments during the last two
decades. Such new norms have to be taken into consideration, and such
new standards given proper weight, not only when States contemplate

new activities but also when continuing with activities begun in the past.
This need to reconcile economic development with protection of the envi-
ronment is aptly expressed in the concept of sustainable development.

For the purposes of the present case, this means that the Parties
together should look afresh at the effects on the environment of the
operation of the GabCikovo power plant. In particular they must find a
satisfactory solution for the volume of water to be released into the old
bed of the Danube and into the side-arms on both sides of the river.

141. It is not for the Court to determine what shall be the final result
of these negotiations to be conducted by the Parties. It is for the Parties
themselves to find an agreed solution that takes account of the objectives
of the Treaty, which must be pursued in a joint and integrated way, as
well as the norms of international environmental law and the principles

of the law of international watercourses. The Court will recall in this con-
text that, as it said in the North Seu Continental Shelfcases:

"[the Parties] are under an obligation so to conduct themselves that
the negotiations are meaningful, which will not be the case when
either of them insists upon its own position without contemplating
any modification of it" (I.C.J. Reports 1969, p. 47, para. 85).

142. What is required in the present case by the rule puctu sunt ser-
vanda, as reflected in Article 26 of the Vienna Convention of 1969on the

Law of Treaties, is that the Parties find an agreed solution within the co-
operative context of the Treaty.
Article 26 combines two elements, which are of equal importance. It
provides that "Every treaty in force is binding upon the parties to it and79 GABCIKOVO-NAGYM PRORECST (JUDGMENT)

must be performed by them in good faith." This latter element, in the
Court's view, implies that, in this case, it is the purpose of the Treaty, and
the intentions of the parties in concluding it, which should prevail over

its literal application. The principle of good faith obliges the Parties to
apply it in a reasonable way and in such a manner that its purpose can be
realized.
143. During this dispute both Parties have called upon the assistance
of the Commission of the European Communities. Because of the dia-
metrically opposed positions the Parties took with regard to the required

outcome of the trilateral talks which were envisaged, those talks did not
succeed. When, after the present Judgment is given, bilateral negotiations
without pre-conditions are held, both Parties can profit from the assist-
ance and expertise of a third party. The readiness of the Parties to accept
such assistance would be evidence of the good faith with which they con-

duct bilateral negotiationsin order to give effect to the Judgment of the
Court.
144. The 1977Treaty not only contains ajoint investment programme,
it also establishes a régime.According to the Treaty, the main structures
of the System of Locks are the joint property of the Parties;their opera-
tion will take the form of a co-ordinated single unit; and the benefits of

the project shall beequally shared.
Since the Court has found that the Treaty is still in force and that,
under its terms, the joint régime is a basic element, it considers that,
unless the Parties agree otherwise, such a régimeshould be restored.

145. Article 10, paragraph 1, of the Treaty states that works of the
System of Locks constituting the joint property of the contracting parties
shall be operated, as a co-ordinated single unit and in accordance with
jointly agreed operating and operational procedures, by the authorized
operating agency of the contracting party in whose territory the works

are built. Paragraph 2 of that Article states that works on the System of
Locks owned by one of the contracting parties shall be independently
operated or maintained by the agencies of that contracting party in the
jointly prescribed manner.
The Court is of the opinion that the works at ~unovo should become
a jointly operated unit within the meaning of Article 10, paragraph 1, in

view of their pivotal role in the operation of what rem+ of the Project
and for the water-management régime. The dam at Cunovo has taken
over the role which was originally destined for the works at Dunakiliti,
and therefore should have a similar status.
146. The Court also concludes that Variant C, which it considers oper-

ates in a manner incompatible with the Treaty, should be made to con-
form to it. By associating Hungary, on an equal footing, in its operation,
management and benefits, Variant C will be transformed from a defacto
status into a treaty-based régime.

It appears from various parts of the record that, given the current state 151. The Court has been asked by both Parties to determine the con-
sequences of the Judgment as they bear upon payment of damages.
According to the Preamble to the Special Agreement, the Parties agreed
that Slovakia is the sole successor State of Czechoslovakia in respect of

rights and obligations relating to the GabCikovo-Nagymaros Project.
Slovakia thus may be liable to pay compensation not only for its own
wrongful conduct but also forthat of Czechoslovakia, and it isentitled to
be compensated for the damage sustained by Czechoslovakia as well as
by itself as a result of the wrongful conduct of Hungary.

152. The Court has not been asked at this stage to determine the quan-
tum of damages due, but to indicate on what basis they should be paid.
Both Parties claimed to have suffered considerable financial losses and
both claim pecuniary compensation for them.
It is a well-established rule of international law that an injured State is
entitled to obtain compensation from the State which has committed an

internationally wrongful act for the damage caused by it. In the present
Judgment, the Court has concluded that both Parties committed interna-
tionally wrongful acts, and it has noted that those acts gave rise to the
damage sustained by the Parties; consequently, Hungary and Slovakia
are both under an obligation to pay compensation and are both entitled
to obtain compensation.

Slovakia is accordingly entitled to compensation for the damage suf-
fered by Czechoslovakia as well as by itself as a result of Hungary's deci-
sion to suspend and subsequently abandon the works at Nagymaros and
Dunakiliti, as those actions caused the postponement of the putting into
operation of the GabCikovo power plant, and changes in its mode of
operation once in service.

Hungary is entitled to compensation for the damage sustained as a
result of the diversion of the Danube, since Czechoslovakia, by putting
into operation Variant C, and Slovakia, in maintaining it in service,
deprived Hungary of its rightful part in the shared water resources, and
exploited those resources essentially for their own benefit.
153. Given the fact, however, that there have been intersecting wrongs

by both Parties, the Court wishes to observe that the issue of compen-
sation could satisfactorily be resolved in the framework of an overall
settlement if each of the Parties were to renounce or cancel al1financial
claims and counter-claims.
154. At the same time, the Court wishes to point out that the settle-
ment of accounts for the construction of the works is different from the

issue of compensation, and must be resolved in accordance with the 1977
Treaty and related :instruments. If Hungary is to share in the operation
and benefits of the Cunovo complex, it must pay a proportionate shareof
the building and running costs.82 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

155. For these reasons,

(1) Having regard to Article 2, paragraph 1, of the Special Agreement,

A. By fourteen votes to one,

Finds that Hungary was not entitled to suspend and subsequently
abandon, in 1989, the works on the Nagymaros Project and on the
part of the GabCikovo Project for which the Treaty of 16 September

1977 and related instruments attributed responsibility to it;

IN FAVOUK : Pre.~identSchwebel; Vice-Prrsident Weeramantry ; Judges
Oda, Bedjaoui, Guillaume, Ranjeva, Shi, Fleischhauer, Koroma,

Vereshchetin, Parra-Aranguren, Kooijmans, Rezek; Judge ad hoc
Skubiszewski ;
AGAINSJ Tu:dge Herczegh;

B. By nine votes to six,

Finds that Czechoslovakia was entitled to proceed, in November
1991, to the "provisional solution" as described in the terms of the
Special Agreement ;

IN FAVOUR : Vice-President Weeramantry ;Judges Oda, Guillaume, Shi,
Koroma, Vereshchetin, Parra-Aranguren, Kooijmans; Judge ad hoc
Skubiszewski ;

AGAINST : President Schwebel ; Judges Bedjaoui, Ranjeva, Herczegh,
Fleischhauer, Rezek;

C. By ten votes to five,
Finds that Czechoslovakia was not entitled to put into operation,

from October 1992, this "provisional solution";
IN FAVOUR : President Schwebel ; Vice-President Weeramantry ;Judges
Bedjaoui, Guillaume, Ranjeva, Herczegh, Shi, Fleischhauer, Kooij-

mans, Rezek;
AGAINST Ju:dges Oda, Koroma, Vereshchetin, Parra-Aranguren; Judge
ad hoc Skubiszewski;

D. By eleven votes to four,

Finds that the notification, on 19 May 1992, of the termination of
the Treaty of 16 September 1977 and related instruments by Hungary
did not have the legal effect of terminating them;

IN FAVOUR:Vice-Pre~ident Weeramantry; Judges Oda, Bedjaoui,
Guillaume, Ranjeva, Shi, Koroma, Vereshchetin, Parra-Aranguren,
Kooijmans; Judge ad hoc Skubiszewski;

AGAINST : President Schwebel ;Judgrs Herczegh, Fleischhauer, Rezek ;Having regard to Article 2, paragraph 2,and Article 5 of the Special
Agreement,

A. By twelve votes to three,

Finds that Slovakia, as successor to Czechoslovakia, became a
party to the Treaty of 16 September 1977 as from 1 January 1993;

IN FAVOUR : President Schwebel ; Vice-President Weeramantry ; Judges
Oda, Bedjaoui, Guillaume, Ranjeva. Shi, Koroma, Vereshchetin,
Parra-Aranguren, Kooijmans: Judge ad hoc Skubiszewski;
AGAINSJ Tu:dges Herczegh, Fleischhauer, Rezek ;

B. By thirteen votes to two,

Finds that Hungary and Slovakia must negotiate in good faith in
the light of the prevailing situation, and must take al1necessary meas-
ures to ensure the achievement of the objectives of the Treaty of
16 September 1977, in accordance with such modalities as they may

agree upon ;
IN FAVOUR P:resident Schwebel; Vice-Prr.sident Weeramantry; Judges
Oda, Bedjaoui, Guillaume, Ranjeva, Shi. Koroma, Vereshchetin,
Parra-Aranguren, Kooijmans, Rezek; Judge ad hoc Skubiszewski;

AGAINST :Judges Herczegh, Fleischhauer ;

C. By thirteen votes to two,
Fin& that, unless the Parties otherwise agree, a joint operational

régimemust be established in accordance with the Treaty of 16 Sep-
tember 1977;
IN FAVOUR : President Schwebel ; Vice-Pre.~identWeeramantry ;Judges
Oda, Bedjaoui, Guillaume, Ranjeva, Shi, Koroma, Vereshchetin,

Parra-Aranguren. Kooijmans, Rezek ;Judge ad hoc Skubiszewski ;

AGAINST :Judges Herczegh, Fleischhauer:

D. By twelve votes to three,

Finds that, unless the Parties otherwise agree, Hungary shall com-
pensate Slovakia for the damage sustained by Czechoslovakia and by
Slovakia on account of the suspension and abandonment by Hun-
gary of works for which it was responsible; and Slovakia shall com-
pensate Hungary for the damage it has sustained on account of the

putting into operation of the "provisional solution" by Czechoslo-
vakia and its maintenance in service by Slovakia;
IN FAVOUR P:resident Schwebel; Vice-Puesident Weeramantry; Judges

Bedjaoui. Guillaume, Ranjeva, Herczegh, Shi, Fleischhauer, Parra-
Aranguren, Kooijmans, Rezek; Judge ad hoc Skubiszewski;
AGAINST J:dges Oda. Koroma, Vereshchetin;84 GABCIKOVO-NAGYM AROOEST(JUDGMENT)

E. By thirteen votes to two,

Finds that the settlement of accounts for tconstruction and
operation of the works must be effected in accordance with the rele-
vant provisions of the Treaty of 16 September 1977 and related
instruments,taking due account of such measures as will have been

taken by the Parties in application of poin2B and 2 C of the
present operative paragraph.
INFAVOUR P:resident Schwebel; Vice-President Weeramantry; Judges
Oda, Bedjaoui, Guillaume, Ranjeva. Shi, Koroma. Vereshchetin,
Parra-Aranguren, Kooijmans, Rezek; Judp ad hoc Skubiszewski;

AGAINST:udges Herczegh, Fleischhauer.

Done in English and in French, the English text being authoritative, at

the Peace Palace, The Hague, this twenty-fifth day of September, one
thousand nine hundred and ninety-seven, in three copies, one of which
will be placed in the archives of the Court and the others transmitted to
the Covernment of the Republic of Hungary and the Government of the
Slovak Republic, respectively.

(Signed) Stephen M. SCHWEBEL,
President.

(Signed) Eduardo VALENCIA-OSPINA,

Registrar.

President SCHWEBEL and Judge REZEKappend declarations to the
Judgment of the Court.

Vice-President WEERAMANTR aYd Judges BEDJAOUIand KOROMA

append separate opinions to the Judgment of the Court.

Judges ODA, RANJEVAH , ERCZEGHF ,LEISCHHAUEV RE, RESHCHETa nd
PARRA-ARANGURE Nd Judge ad hoc SKUBISZEWSa KpIpend dissenting
opinions to the Judgment of the Court.

(Initiullcd) S.M.S.
(Initialled) E.V.O.

Bilingual Content

INTERNATIONAL COURT OF JUSTICE

REPORTS OF JUDGMENTS,
ADVISORY OPINIONS AND ORDERS

CASE CONCERNING
THE GABCIKOVO-NAGYMAROS PROJECT

(HUNGARYISLOVAKIA)

JUDCMENT OF 25 SEPTEMBER 1997

COUR INTERNATIONDE JUSTICE

RECUEIL DES ARRÊTS,
AVIS C:ONSULTATIFS ET ORDONNANCES

AFFAIRE RELATIVE AU PROJET

GA.BCIKOVO-NAGYMAROS

(HONGRIEISLOVAQUIE)

ARRÊT DU 25 SEPTEMBRE 1997 Official citati:n
GabCikovo-NagymarosProject (HungarylSlovakia),
Judgment, 1.C.J. Reports1997, p. 7

Mode officiede citation:
Projet GabCikovo-Nagymaros (HongrielSlovaquie),
arrêt,C.I.J. Recueil1997, p. 7

Sales number
ISSN 0074-4441 Node vente: 692

ISBN 92-1-070757-5 25 SEPTEMBER 1997

JUDGMENT

GABC~KOVO-NACYMAROS PROJECT

(HUNGARYISLOVAKIA)

PROJET GABCIKOVO-NAGYMAROS

(HONGRIEISLOVAQUIE) INTERNATIONAL COURT OF JUSTICE

1997 YEAR 1997
25 September
General List
No. 92 25 September1997

CASE CONCERNING

THE GABC~KOVO-NAGYMAROS PROJECT

(HUNGARYISLOVAKIA)

Treaty of 16 September 1977 concerning the construction and operation of
the GabCikovo-Nugymaros Systenz of Locks - "Related instruments".
Suspension and abandonment by Hungary, in 1989, oj'works on the Project

- Applicability of the Vienna Convention of 1969 on the Law of Treaties -
Law of treaties and law of State responsibility - Stute of necessity as a ground
jor precluding the wrongfulness of an act - "Essential interest" of the State
committing the act - Environment - "Grave und imminent peril" - Act

having to constitute the "only means" of saj&guardingthe interest threatened -
State having "contributed to the occurrence of the state of necessity".
Czechoslovakia:~proceeding, in November 1991, to "Variant C" andputting
into operation, from October 1992, this Variant - Arguments drawn from a
proposed principle of approximate application - Respect for the limits of the

Treaty - Right to an equitahle and reasonable share of rhe resources of an
international wutercourse - Commission of a wrongful act andprior conduct of
a prepararory character - Obligation to mitigate damages - Principle con-
cerning only the calculation of damages - Countermeasures - Response to an

internationally wrongful act - Proportionality - Assumption of unilateral
control of a shared resource.
Notification by Hungary, on 19 May 1992, of the fermination of the 1977
Treaty and reluted instruments - Legal efjrects - Matter falling within the law

of treaties - Articles 60 to 62 of the Vienna Convention on the Law of Trearies
- Customury law - lmpossihility of performance - Permanent disappearance
or destruction of an "object" indispensablefor execution - Impossibility of prr-
formance resulting from the hreach, by the party invoking il, of an obligation
under the Treaty - Fundamental change of circumstances - Essential basis of

the consent of the parties - Extent of obligations still to be performed - Sta-
bility of treaty relations - Material breach of the Treaty - Date on which the
breach occurred and date of notijïcation of termination - Victim of a breach
having itselfcommitted a prior breach of the Treaty - Emergence of new norms
of environmental law - Sustainable development - Treaty provisions permit- COUR INTERNATIONALE DE JUSTICE

ANNÉE 1997 1997
25 septembre
Rôle général
25 septembre1997 no92

AFFAJRE RELATIVE AU PROJET

GP~BCIKOVO-NAGYMAROS

(HONGRIEISLOVAQUIE)

Traitédu 16 septembre 1977 relatif à lu construction et aufonctionnement du
système d'éclusesde GabEikovo-Nagymaros - ((Instruments y afJrrents )>.
Suspension et abandon par la Hongrie, en 1989, de travaux relatifs au projet

- Applicubilité de lu convention de Vienne de 1969 sur le droit des traités -
Droit des traitéset droit de la responsabilité desEtats - Etat de nécessitéen
tant que cuuse d'exclusion de l'illicéitéd'unfait - ((Intérêe tssentiel)) de I'Etat
auteur du,fait - Environnement - «Péril grave et imminent » - Fait devant
constituer le «seul moyen» de sauvegarder l'intérêten cause - Etat ayant

« contribuci à la survenance de Ietat de nécessité)).
Recourspar la Tchécoslovaquie,en novembre 1991, à la ((variante C» et mise
en service. u partir d'octobre 1992. de cette variante - Argumentation tirée
d'unprincipe alléguc? d'application pur approximation - Respect des limites du
traité - Droit à une part équitable et raisonnable des ressources d'un cours
d'eau international - Réalisation d'un fait illicite et comportement antérieur

présentant un caractère préparatoire - Obligation d'utténuerles dommages -
Principe concernant seulenlent le calcul de dommages et intérêts - Confre-
mesures - Riposte, à un fait internationulement illicite - Proportionnalité
- Prise de contrôle unilatéraled'une ressource partagée.
Notijïcation par /a Hongrie, le 19 mai 1992, de lu terminaison du traité de

1977 et des instrumtwts y afférents - Efits juridiques - Question relevant du
droit des truités - Articles 60 à 62 de lu convention de Vienne sur le droit des
traités - Droit coutumier - Impossibilité d'exécution - Disparition ou des-
truction &$nit ives d'un « objetw indispensable à / 'exécution - Impossibilité
d'exécution résu1tar;ldte la violation, par lapartie qui l'invoque,d'une obligation

découlantdu traité -- Changementfondamental de circonstances - Base essen-
tielle du consenteml-nt des parties - Portéedes obligations restant à exécuter
- Stabilité des relations conventionnelles - Violation substantielle du traité -
Dute à laquel/e la violation a étécommise et date de la nottjicution de termi-
naison - Victime d'une violation ayant elle-mêmecommis une violation pré-
alable du truité - Emergence de nouvelles normes du droit de l'environnement8 GABC~KOVO-NAGYMA PRROJSCT (JUDGMENT)

ting the parties, by mutual consent, to take account of those norms - Repudia-
tion of the Treaty - Reciprocal non-compliance - Integrity of the rule pacta
sunt servanda - Treaty remaining inforce until terminated by mutual consent.

Legal consequences of the Judgment of the Court - Dissolution of Czecho-

slovakia - Article 12 of the Vienna Convention of 1978on Succession of States
in respect of'Treaties - Customary laiv - Succession of States without effect
on a treaty creating rights and obligations "attaching" to the territory -
Irregular state of uffairs as a result of failure of both Parties to comply with
their treaty obligations - Ex injuria jus non oritur - Objectives of the Treaty
- Obligations overtaken by events - Positions adopted by the parties after

conclusion of the Treaty - Goodfaith negotiations - Effects of the Project on
the environment - Agreed solution to befound by the Parties - Joint régime
- Reparation for arts committed by both Parties - Co-operation in the use of
shared water resources - Damages - Succession in respect of rights and obli-
gations relating to the Project - Intersecting ivrongs- Settlement of accounts
for the construction of the works.

JUDGMENT

Present: President SCHWEBEL V;ice-President WEERAMANTRJY u; ges ODA,

BEDIAOUIG , UILLAUMR EA, NJEVA,HERCZEGHS ,HI, FLEISCHHAUER,
KOROMAV , ERESHCHET PINR, RA-ARANGUREN, KOOIJMANS R,EZEK;
Judge ad hoc SKUBISZEW ;SKeIgistrar VALENCIA-OSPINA.

In the case concerning the GabCikovo-Nagymaros Project,

between

the Republic of Hungary,
represented by

H.E. Mr. Gyorgy Szénasi,Ambassador, Head of the International Law
Department, Ministry of Foreign Affairs,
as Agent and Counsel;

H.E. Mr. DénesTomaj, Ambassador of the Republic of Hungary to the
Netherlands,

as Co-Agent ;
Mr. James Crawford, Whewell Professor of International Law, University of
Cambridge,
Mr. Pierre-Marie Dupuy, Professor at the University Panthéon-Assas

(Paris II) and Director of the Institut des hautes études internationales
of Paris,
Mr. Alexandre Kiss, Director of Research, Centre national de la recherche
scientifique (retd.),
Mr. Laszlo Valki, Professor of International Law, Eotvos Lorand Univer-
sity, Budapest, PROJET GABCIKOVO-NAGYMAROS (ARRÉT) 8

- Développement durable - Dispositions dzt traité permettant aux parties,
d'un commun accord, de tenir compte de ces normes - Rejet du traité - Man-

quements réciproques - Intégritéde la règle pacta sunt servanda - Traité
demeurant en vigueur tant qu'il n'y est pas mis jn d'un commun accord.
Conséquences juriu'iques de l'arrêtde lu Cour - Dissolution de la Tchéco-
.rlovaquie -- Article 12 de la convention de Vienne de 1978 sur la succession
d'Etats en matière de traités - Droit coutumier - Succession d'Etats sans
incidence sur un traité créant desdroits et obligations ((attachés» au territoire

- Situation irrégulière dueaux manquements des deu.uParties à leurs obliga-
tions conventionnel1e.r - Ex injuria jus non oritur - Objectifs du traité -
Obligations de passée.p ^ar les événements - Positions adoptéespar les parties
aprèsla coriclusiondzttraité - Négociationsde bonnefoi - Incidences dupro-
jet sur l'environneme~zt - Solution à trouver de commun uccord pur les Parties

- Régime rolljoint -- Réparation des actes commis par les deux Parties -
Coopérationpour Iuiilisation des ressources en eau partagées - Dommages et
intérêts- Successiorien ce qui concerne les droits et obligations relat~x~aupro-
jet - Acies illicites croisés - Règlement des comptes concernant la construc-
tion des ouvrages.

Présents : M. SCHWEBELP ,résident; M. WEERAMANTRY V,ice-Président ;
MM. OL)A, BEDJAOUIG , UILLAUMER ,ANJEVA,HERCZEGHS , HI,
FLEISCHHAUE KRO,ROMA V,ERESHCHETP INA,RRA-ARANGURK ENO, IJ-
MANSR , EZEKj,uges; M. SKUBI~ZEW~ jugIe, ad hoc; M. VALENCIA-

OSPINAG , refjer.

En l'affaire relative au projet GabCikovo-Nagymaros,

entre
la République de Hongrie,

représentéepar

S. Exc. M. Gyorgy Szénasi,ambassadeur, directeur du département de droit
international au ministère des affaires étrangères,
comme agent et conseil;

S. Exc. M. DénesTomaj, ambassadeur de la République de Hongrie aux
Pays-Bas,
comme coagent ;

M. James Crawford, professeur de droit international, titulaire de la chaire
Whewell a l'université de Cambridge,
M. Pierre-Marie Dupuy, professeur a l'université Panthéon-Assas (ParisII)
et directeur de l'Institut des hautes étudesinternationales de Paris,

M. Alexandre Kiss, directeur de recherches au Centre national de la re-
cherche scientifique (en retraite),
M. Laszlo Valki, professeur de droit international a l'université Eotvos
Lorand de Budapest, GABCIKOVO-NAGYMAROSPROJECT(JUDGMENT)

Mr. Boldizsar Nagy, Associate Professor of International Law, Eotvos
Lorand University, Budapest,
Mr. Philippe Sands, Reader in International Law, University of London,
School of Oriental and African Studies, and Global Professor of Law,
New York University,

Ms Katherine Gorove, consulting Attorney,
as Counsel and Advocates;
Dr. Howard Wheater, Professor of Hydrology, Imperia1College, London,
Dr. Gabor Vida, Professor of Biology, Eotvos Lorand University, Budapest,

Member of the Hungarian Academy of Sciences,
Dr. Roland Carbiener, Professor emeritus of the University of Strasbourg,
Dr. Klaus Kern, consulting Engineer, Karlsruhe,
as Advocates;
Mr. Edward Helgeson,

Mr. Stuart Oldham,
Mr. PéterMolnar,
as Advisers;
Dr. Gyorgy Kovacs,
Mr. Timothy Walsh,

Mr. Zoltan Kovacs,
as Technical Advisers ;
Dr. Attila Nyikos,

as Assistant ;
Mr. Axe1Gosseries, LL.M.,

as Translator ;
Ms Éva Kocsis,
Ms Katinka Tompa,

as Secretaries,
and

the Slovak Republic,
represented by

H.E. Dr. Peter Tomka, Ambassador, Legal Adviser of the Ministry of For-
eign Affairs,
as Agent;

Dr. Vaclav Mikulka, Member of the International Law Commission,
as Co-Agent, Counsel and Advocate;

Mr. Derek W. Bowett, C.B.E., Q.C., F.B.A., Whewell Professor emeritus of
International Law at the University of Cambridge, former Member of the
International Law Commission,
as Counsel ;
Mr. Stephen C. McCaffrey, Professor of International Law at the University
of the Pacific, McGeorge School of Law, Sacramento, United States of

America, former Member of the International Law Commission,
Mr. Alain Pellet, Professor at the University of Paris X-Nanterre and at the M. Boldizsar Nagy, professeur associéde droit international à l'université
Eotvos Lorand (le Budapest.
M. Philippe Sand:;, chargé de cours de droit international à la School of
Oriental and African Studies de l'université de Londres, etGlobal Profes-
sor of Law à l'Universitéde New York.
MmeKatherine Gorove, juriste-conseil,

comme conseils et avocats;
M. Howard Wheater, professeur d'hydrologie àl'Imperia1College de Londres,
M. Gabor Vida, professeur de biologie à l'université Eotvos Lorand de
Budapest. membre de l'Académiedes sciences de Hongrie,
M. Roland Carbiener, professeur éméritede l'université de Strasbourg,

M. Klaus Kern, in.génieur-conseià Karlsruhe,
comme avocats;
M. Edward Helgeson,
M. Stuart Oldham,,

M. PéterMolnar,
comme conseillers :
M. Gyorgy Kovacs,
M. Timothy Walsh,

M. Zoltan Kovacs,
comme conseillers techniques;
M. Attila Nyikos,

comme assistant;
M. Axel Gosseriesi, LL.M.,

comme traducteur ;
Mm' Eva Kocsis,
Mn" Katinka Tonnpa,

comme secrétaires,

la République slovaque.

représentéepar
S. Exc. M. Peter Tomka, ambassadeur, conseiller juridique du ministère des
affaires étrangères.

comme agent;
M. Vaclav Mikullta, membre de la Commission du droit international,

comme coagent, c.onseilet avocat;
M. Derek W. Bowett, C.B.E., Q.C., F.B.A.. professeur émérite, ancien titu-
laire de la chaire Whewellà l'université de Cambridge, ancien membre de
la Commission du droit international,

comme conseil ;
M. Stephen C. McCaffrey. professeur de droit international à la McGeorge
School of Law de l'université du Pacifique à Sacramento (Etats-Unis
d'Amérique), ancien membre de la Commission du droit international.
M. Alain Pellet, professeurà l'université de Paris X-Nanterre età l'Institut Institute of Political Studies, Paris, Member of the International Law
Commission,
Mr. Walter D. Sohier, Member of the Bar of the State of New York and of
the District of Columbia,
Sir Arthur Watts, K.C.M.G., Q.C., Barrister, Member of the Bar of England
and Wales,
Mr. Samuel S. Wordsworth, avocat à la cour d'appel de Paris, Solicitor of
the Supreme Court of England and Wales, Frere Cholmeley, Paris,

as Counsel and Advocates;
Mr. Igor Mucha, Professor of Hydrogeology and Former Head of the
Groundwater Department at the Faculty of Natural Sciencesof Comenius
University in Bratislava,
Mr. Karra Venkateswara Rao, Director of Water Resources Engineering,
Department of Civil Engineering, City University, London,

Mr. Jens Christian Refsgaard, Head of Research and Development, Danish

Hydraulic Institute,
as Counsel and Experts;
Dr. Cecilia KandraCova, Director of Department, Ministry of Foreign
Affairs,
Mr. Ludëk Krajhanzl, Attorney at Law, Vyroubal Krajhanzl Skacel and

Partners, Prague,
Mr. Miroslav LiSka, Head of the Division for Public Relations and Exper-
tise, Water Resources Development State Enterprise, Bratislava,

Dr. Peter VrSansky, Minister-Counsellor, Chargé d'affaires a.i.o ,f the
Embassy of the Slovak Republic, The Hague,
as Counsellors ;

Miss Anouche Beaudouin, allocataire de recherche at the University of
Paris X-Nanterre,
Ms Cheryl Dunn, Frere Cholmeley, Paris,
Ms Nikoleta GI!ndova, attaché, Ministry of Foreign Affairs,
Mr. Drahoslav Stefanek, attaché, Ministry of Foreign Affairs,
as Legal Assistants,

composed as above,
after deliberation,

delivers thefollowing Judgment ;

1. By a letter dated 2 July 1993, filed in the Registry of the Court on the
same day, the Ambassador of the Republic of Hungary (hereinafter called
"Hungary") to the Netherlands and the Chargéd'affaires ad interim of the Slo-
vak Republic (hereinafter called "Slovakia") to the Netherlands jointly notified
to the Court a Special Agreement in English that had been signed at Brussels
on 7 April 1993and had entered into force on 28 June 1993,on the date of the
exchange of instruments of ratification.
2. The text of the Special Agreement reads as follows: d'études politiquesde Paris, membre de la Commission du droit interna-
tional,
M. Walter D. Sohier, membre des barreaux de 1'Etat de New York et du
district de Columbia,
sir Arthur Watts, K.C.M.G., Q.C., Barrister, membre du barreau d'Angle-
terre et du pays de Galles,
M. Samuel S. Wordsworth, avocat à la cour d'appel de Paris et Solicitor
auprès de la Cour suprêmed'Angleterre et du pays de Galles, Frere Chol-

meley, Paris,
comme conseils et avocats;
M. Igor Mucha, professeur d'hydrogéologieet ancien directeur du départe-
ment des eaux s,outerrainesà la faculté dessciencesnaturelles de l'univer-
sitéComenius de Bratislava,
M. Karra Venkateswara Rao, directeur de la section des techniques d'amé-

nagement hydrauliques du départementdu géniecivilde la City University
de Londres,
M. Jens Christian Refsgaard, directeur de la recherche et du développement
à l'Institut danois d'hydraulique,
comme conseils et experts;
Mn" Cecilia KandraEova. directeur de département au ministèredes affaires

étrangères,
M. Ludt-k Krajhanzl, avocat, cabinet Vyroubal Krajhanzl Skacel et associés,
Prague,
M. Miroslav LiSka, directeur de la division des relations publiques et de
l'expertise de1i:ntreprised'Etat pour la mise en valeur des ressources en
eau. Bratislava,
M. Peter VrSansky, ministre conseiller, chargé d'affaires par intérim de
l'ambassade de la République slovaque aux Pays-Bas.
comme conseillers;

Ml1'Anouche Beaudouin, allocataire de recherche a l'université de Paris
X-Nanterre,
MmeCheryl Dunri, Frere Cholmeley, Paris,
Mn" Nikoleta Clindova, attachéeau ministèredes affaires étrangères,
M. Drahoslav Stefanek, attachéau ministère des affaires étrangères,
comme assistants juridiques,

ainsi composée,
après délibéré en (chambredu conseil,

rend 1'urrt;tsuivant;

1. Par lettre en date du 2juillet 1993,déposéeau Greffe de la Cour le même
jour, l'ambassadeur aux Pays-Bas de la Républiquede Hongrie (dénomméeci-
après la «Hongrie») et le chargé d'affaires par intérim aux Pays-Bas de la
République slovaque (dénomméeci-aprèsla «Slovaquie») ont notifiéconjoin-
tement àla Cour un compromis en langue anglaise, signéa Bruxelles le 7 avril
1993et entré en vigueur le 28 juin 1993à la date de l'échangedes instruments
de ratification.
2. Dans sa traduction française, le texte du compromis se lit comme suit: GABcIKOVO-NAGYMAROS PROJECT (JUDGMENT)

"The Republic of Hungary and the Slovak Rcpublic,

Considering that differences have arisen between the Czech and Slovak
Federal Republic and the Republic of Hungary regarding the implementa-
tion and the termination of the Treaty on the Construction and Operation
of the Gabtikovo-Nagymaros Barrage System signed in Budapest on
16September 1977and related instruments (hereinafter referred to as 'the
Treaty'), and on the construction and operation of the 'provisional solu-
tion';
Beuring in nlind that the Slovak Republic is one of the two successor
States of the Czech and Slovak Federal Republic and the sole successor
State in respect of rights and obligations relating to the GabCikovo-Nagy-

maros Project ;
Recognizing that the Parties concerned have been unable to settle these
differences by negotiations;
Huving in rnind that both the Czechoslovak and Hungarian delegations
expressed their commitment to submit the differences connected with the
GabCikovo-Nagymaros Project in al1 its aspects to binding international

arbitration or to the International Court of Justice;
Desiring that these differences should be settled by the International
Court of Justice;
Reculling their commitment to apply, pending the Judgment of the
International Court of Justice, such a temporary watermanagement régime
of the Danube as shall be agreed between the Parties;

Desiring further to define the issues to be submitted to the International
Court of Justice.
Have agreed as follows :

Article I

The Parties submit the questions contained in Article 2 to the Interna-
tional Court of Justice pursuant to Article 40, paragraph 1, of the Statute
of the Court.

Article 2
(1) The Court is requested to decide on the basis of the Treaty and rules
and principles of general international law. as well as such other treaties as
the Court may find applicable,

(a) whether the Republic of Hungary was entitled to suspend and subse-
quently abandon, in 1989, the works on the Nagymaros Project and
on the part of the GabCikovo Project for which the Treaty attributed
responsibility to the Republic of Hungary:
(b) whether the Czech and Slovak Federal Republic was entitled to pro-
ceed, in November 1991,to the 'provisional solution' and to put into
operation from October 1992this system, described in the Report of
the Working Group of Independent Experts of the Commission of
the European Communities, the Republic of Hungary and the Czech
and Slovak Federal Republic dated 23 November 1992(damming up
of the Danube at river kilometre 1851.7 on Czechoslovak territory

and resulting consequences on water and navigation coufse); «La Républiquede Hongrie et la Républiqueslovaque,

Considérantque des contestations ont surgi entre la République fédéra-
tive tchèque et slovaque et la République de Hongrie concernant I'applica-
tion et la termiriaison du traité relatàfla construction et au fonctionne-
ment du systèmede barrage de Gabtikovo-Nagymaros, signéa Budapest
le 16septembre 1977,et des instruments y afférents (ci-aprèsdénommésle
«traité»). ainsi que la construction et le fonctionnement de la «solution
provisoire»;

Tenant compte de ce que la République slovaque est l'un des deux Etats
successeurs de la République fédérative tchèqueet slovaque et l'unique
Etat successeur en ce qui concerne les droits et obligations relatifs au pro-
jet Gabtikovo-Pdagymaros;
Reconnaissani que les parties concernées ne sont pas parvenues à régler
ces contestations par voie de négociation;

Ajlunrà Iksprit que tant la délégation tchécoslovaqueque la délégation
hongroise ont déclaréqu'elles s'engageaient à soumettre les contestations
liéesau projet Ciabtikovo-Nagymaros sous tous ses aspects à un arbitrage
international obligatoire ou à la Cour internationale de Justice;
Souhaitant que ces contestations soient régléespar la Cour internatio-
nale de Justice;

Rappelant qu'elles se sont engagées à appliquer, en attendant l'arrêtde
la Cour internationale de Justice, le régimetemporaire de gestion des eaux
du Danube dont seront convenues les Parties;
De'sirunten outre définirles questionsà soumettre à la Cour internatio-
nale de Justice,

Sont convenues de ce qui suit

ArtirI~,premier
Les Parties soumettent à la Cour internationale de Justice, conformé-
ment au paragraphe 1 de l'article 40 du Statut de la Cour, les questions
énoncées à l'article 2 ci-après.

Article 2

1) La Cour est priéede dire, sur la base du traité et des règleset prin-
cipes du droit international général,ainsi que de tous autres traités qu'elle
jugera applicables :

a) si la République de Hongrie était en droit de suspendre puis d'aban-
donner, en 1989,lestravaux relatifs au projet de Nagymaros ainsi qu'à
la partie du projet de Gabtikovo dont la République de Hongrie est
responsable aux termes du traité;
b) si la Répukiliquefédérativetchèque et slovaque était en droit de re-
courir, en novembre 1991, à la «solution provisoire» et de mettre en
service.à partir d'octobre 1992, ce système, décritdans le rapport en
date du 23 novembre 1992du groupe de travail d'experts indépendants
nominéspar la Commission des Comm~inautéseuropéennes, la Répu-
blique de Hongrie et la République fédérativetchèque et slovaque
(constructic)n d'un barrage sur le Danube au kilomètre 1851,7 du

fleuve, en territoire tchécoslovaque, et conséquences en résultant pour
I'écoulemen~dtes eaux et la navigation);12 GABC~KOVO-NAGYMAROSPROJECT(JUDGMENT)

(c) what are the legal effects of the notification, on 19 May 1992,of the
termination of the Treaty by the Republic of Hungary.
(2) The Court is also requested to determine the legal consequences,

including the rights and obligations for the Parties, arising from itsudg-
ment on the questions in paragraph 1 of this Article.
Article 3

(1) Al1questions ofprocedure and evidenceshall be regulated in accord-
ance with the provisions of the Statute and the Rules of Court.
(2) However. the Parties request the Court to order that the written
proceedings should consist of:
(LI) a Memorial presented by each of the Parties not later than ten
months after the date of notification of this Special Agreement to the
Registrar of the International Court of Justice;
(hi a Counter-Memorial presented by each of the Parties not later than
seven months after the date on which each has received the certified
copy of the Memorial of the other Party;
(ci a Reply presented by each of the Parties within such time-limits as the
Court may order.

(d) The Court may request additional written pleadings by the Parties if
it so determines.
(3) The above-mentioned parts of the written proceedings and their
annexes presented to the Registrar will not be transmitted to the other
Party until the Registrar has received the corresponding part of the pro-
ceedings from the said Party.

Article 4
(1) The Parties agree that, pending the final Judgment of the Court,
they will establish and implement a temporary water management régime
for the Danube.
(2) They further agree that, in the period before such a régimeis estab-
lished or implemented, if either Party believesits rights are endangered by
the conduct of the other, it may request immediate consultation and ref-
erence, if necessary, to experts, including the Commission of the European
Communities, with a view to protecting those rights; and that protection
shall not be sought through a request to the Court under Article 41 of the

Statute.

(3) This commitment is accepted by both Parties as fundamental to the
conclusion and continuing validity of the Special Agreement.
Article 5

(1) The Parties shall accept the Judgment of the Court as finaland bind-
ing upon them and shall execute it in its entirety and in good faith.
(2) Immediately after the transmission of the Judgment the Parties shall
enter into negotiations on the modalities for its execution.
(3) If they are unable to reach agreement within six months, either
Party may request the Court to render an additional Judgment to deter-
mine the modalities for executing its Judgment.
Article 6

(1) The present Special Agreement shall be subject to ratification.c) qterminaison du traité par la République de Hongrie.le 19mai 1992,de la

2) La Cour est égalementpriéede déterminer les conséquences juridi-
ques, y compris les droits et obligations pour les Parties, de I'arrêt qu'elle
rendra sur les questions énoncéesau paragraphe1 du présent article.
Article 3

1)Toutes les questions de procédure etde preuve seront réglconfor-
mémentaux disipositionsdu Statut et du Règlementde la Cour.
2) Toutefois, les Parties prient la Cour de bien vouloir ordonner que la
procédure écritecomprenne les piècessuivantes:
a) un mémoire présenté par chacune des Parties au plus tard dix mois
après la datede la notification du présent compromis au Greffier de la
Cour internationale de Justi;e
b) un contre-mémoire présenté par chacune des Parties au plus tard sept
mois après la date à laquelle chacune aura reçu la copie certifiée
conforme di1mémoirede I'autre Partie;
L.) une répliqueprésentéepar chacune des Parties dans les délaisque la
Cour indiquera.
d) La Cour pourra, si elle lejuge utile, demander aux Parties de déposer
des piècesdl: procédure écrite supplémentaires.

3) Les pièce:;de procédure écrite susmentionnées et leurs annexes,
déposées aupréijdu Greffier, ne seront transmises i I'autre Partie que
lorsque le Greffier aura reçu de ladite Partie la piècede procédure corres-
pondante.
Article 4

1) Les Parties conviennent, en attendant I'arrêtdéfinitifde la Cour.
d'établir etd'appliquer un régimetemporaire de gestion des eaux pour le
Danube.
2) Les Parties.conviennent en outre qu'au cas où,au cours de la période
précédantl'établissement ou l'application d'un tel régime,l'une d'entre
elles considéreriiitque la conduite de l'autrese1 droits en danger, elle
pourra demander des consultations immédiates et, au besoin, qu'il soit
recouru à des experts, y compris la Commission des Communautés euro-
péennes, en vuede protégerces droits; et que la protection de ces droits ne
sera pas recherchéeau moyen d'une demande présentéea la Cour en vertu
de l'article1 du Statut.
3) Les deux Parties acceptent cet engagement en tant qu'élémentfonda-
mental de la conclusion et du maintien de la validitédu compromis.
Article 5

1)Les Partie:; s'engageàtaccepter I'arrêtde la Cour comme définitif et
obligatoire pour elles àtl'exécuterintégralement etde bonne foi.
2) Aussitôt que I'arrêtleur aura été remis,les Parties engageront des
négociationspour fixer lesmodalitésde son exécution.
3) Si lesParties ne peuvent parvenirà un accord dans un délaide six
mois, l'une ou I'autre d'entre elles pourra prier la Cour de rendre un arrêt
supplémentaire pour déterminerles modalités d'exécutionde son arrêt.
Article 6

1) Le présentcompromis est soumis à ratification (2) The instruments of ratification shall be exchanged as soon as pos-
sible inBrussels.
(3) The present Special Agreement shall enter into force on the date of
exchange of instruments of ratification. Thereafter it willbe notifiedjointly
to the Registrar of the Court.
In witness whereof the undersigned being duly authorized thereto, have
signed the present Special Agreement and have affixed thereto their seals."

3. Pursuant to Article 40, paragraph 3, of the Statute and Article 42 of the
Rules of Court, copies of the notification and of the Special Agreement were
transmitted by the Registrar to the Secretary-General of the United Nations,
Members of the United Nations and other States entitled to appear before the
Court.
4. Since the Court included upon the Bench no judge of Slovak nationality,
Slovakia exercised its right under Article 31, paragraph 2, of the Statute to
choose a judge ad hoc to sit in the case: it chose Mr. Krzysztof Jan Skubi-
szewski.

5. By an Order dated 14July 1993,the Court fixed 2 May 1994as the time-
limit for the filing by each of the Parties of a Memorial and 5 December 1994
for the filing by each of the Parties of a Counter-Memorial. having regard to
the provisions of Article 3, paragraph 2 (a) and (b), of the Special Agreement.
Those pleadings were duly filed within the prescribed time-limits.

6. By an Order dated 20 December 1994, the President of the Court,
having heard the Agents of the Parties, fixed 20 June 1995 as the time-limit
for the filing of the Replies, having regard to the provisions of Article3, para-
graph 2 (c), of the Special Agreement. The Replies were duly filed within the
time-limit thus prescribed and, as the Court had not asked for the submission
of additional pleadings, the case was then ready for hearing.
7. By letters dated 27 January 1997,the Agent of Slovakia, referring to the
provisions of Article 56,paragraph 1,of the Rules of Court, expressed his Gov-
ernment's wish to produce two new documents; by a letter dated 10 February
1997, the Agent of Hungary declared that his Government objected to their
production. On 26 February 1997, after having duly ascertained the views of
the two Parties, the Court decided, in accordance with Article 56, paragraph 2,
of the Rules of Court, to authorize the production of those documents under

certain conditions of which the Parties were advised. Within the time-limit fixed
by the Court to that end, Hungary submitted comments on one of those docu-
ments under paragraph 3 of that same Article. The Court authorized Slovakia
to comment in turn upon those observations, as it had expressed a wish to do
so; its comments were received within the time-limit prescribed for that pur-
pose.
8. Moreover, each of the Parties asked to be allowed to show a video cas-
sette in the course of the oral proceedings. The Court agreed to those requests,
provided that the cassettes in question were exchanged in advance between the
Parties, through the intermediary of the Registry. That exchange was effected
accordingly.
9. In accordance with Article 53, paragraph 2, of the Rules of Court. the
Court decided, after having ascertained the views of the Parties. that copies of
the pleadings and documents annexed would be made available to the public as
from the opening of the oral proceedings.
10. By a letter dated 16June 1995,the Agent of Slovakia invited the Court PROJETGABCIKOVO-NAGYMAROS(ARRÊT) 13

2) Les instruments de ratification seront échangésaussitôt que possiblà
Bruxelles.
3) Le présent c:ompromis entrera en vigueur à la date de l'échange des
instruments de ratification. II fera ensuite l'objet d'une notification
conjointe au Greffier de la Cour.

En foi de quoi les soussignés,dûment habilités à cet effet, ont signéle
présent compromis et y ont apposé leur sceau. »

3. Conformément au paragraphe 3 de l'article 40 du Statut et àl'article 42
du Règlement de la Cour, des copies de la notification et du compromis ont été
transmises par le Greffier au Secrétaire généralde l'organisation des Nations
Unies, aux Membres des Nations Unies et aux autres Etats admis à ester
devant la Cour.
4. La Cour ne comptant pas sur le siègede juge de nationalité slovaque, la
Slovaquie s'est prévaluedu droit que lui confère le paragraphe 2 de l'article 31
du Statut de procéder à la désignation d'un juge ud hoc pour siéger enl'affaire:
elle a désignéà cet effet M. Krzysztof Jan Skubiszewski.
5. Par ordonnance en date du 14juillet 1993,la Cour a fixéau 2 mai 1994la
date d'expiration du délaipour le dépôt d'un mémoirepar chaque Partie, et au

5 décembre 1994la date d'expiration du délaipour le dépôt par chacune d'elles
d'un contre-mémoire. eu égardaux dispositions de l'article 3, paragraphe 2, ali-
néas a) et h), du ccimpromis. Ces pièces ont étédûment déposéesdans les
délais ainsi prescrits.
6. Par ordonnance. en date du 20 décembre 1994, le Président de la Cour,
après avoir entendu les agents des Parties. a fixéau 20juin 1995 la date d'expi-
ration du délaipour le dépôt des répliques, eu égard aux dispositions de I'ar-
ticle 3. paragraphe 2. alinéac), du compromis. Les répliques ont étédûment
déposéesdans le délaiainsi prescrit et. la Cour n'ayant pas demandéla produc-
tion de piècessupplé:mentaires,l'affaire s'est alors trouvéeen état.
7. Par lettres du 27janvier 1997,l'agent de la Slovaquie, se référantaux dis-
positions du paragraphe 1 de l'article 56 du Règlement, a expriméle désirde
son gouvernement tie produire deux nouveaux documents; par lettre du

10 février 1997, l'agent de la Hongrie a fait savoir que son gouvernement s'y
opposait. Le 26 février 1997, après avoir dûment recueilli les vues des deux
Parties, la Cour a décidé,conformément au paragraphe 2 de l'article 56 du
Règlement. d'autoriser la production de ces documents sous certaines condi-
tions dont les Parties ont étéavisées.Dans le délaifixépar la Cour àcet effet,
la Hongrie a présenté desobservations au titre du paragraphe 3 du mêmear-
ticle sur l'un de ces documents. La Cour a autoriséla Slovaquie, comme celle-ci
en avait exprimé le s.ouhait,à soumettre à son tour des commentaires sur ces
observations; lesdits commentaires ont étéreçus dans le délaiprescrit à cette
fin.
8. Chacune des Parties a en outre demandé de pouvoir présenter une vidéo-
cassette au cours de la procédure orale. La Cour a accédé à ces demandes, à la

condition que les cassettes en question soient au préalable échangéesentre les
Parties par l'entremise du Greffe.Il a ainsi étéprocédé.

9. Conformément au paragraphe 2 de l'article 53 du Règlement. la Cour a
décidé,après s'êtrerenseignée auprès des Parties, que des exemplaires des
pièces de procédure et des documents y annexés seraient rendus accessibles
au public iicompter de l'ouverture de la procédure orale.
10. Par lettre en date du 16juin 1995.l'agent de la Slovaquie avait invitéla14 GAB~IKOVO-NAGYMAROS PROJECT (JUDGMENT)

to visit the locality to which the case relates and there to exercise its functions
with regard to the obtaining of evidence, in accordance with Article 66 of the
Rules of Court. For his part, the Agent of Hungary indicated, by a letter dated
28 June 1995,that, if the Court should decide that a visit of that kind would be
useful, his Government would be pleased to co-operate in organizing it. By a
letter dated 14November 1995,the Agents of the Parties jointly notified to the
Court the text of a Protocol of Agreement, concluded in Budapest and New
York the same day, with a view to proposing to the Court the arrangements
that might be made for such a visitinsitu; and, by a letter dated 3 February
1997,they jointly notified to it the text of Agreed Minutes drawn up in Buda-
pest and New York the same day, which supplemented the Protocol of Agree-
ment of 14 November 1995. By an Order dated 5 February 1997, the Court

decided to accept the invitation to exercise its functions with regard to the
obtaining of evidence at a place to which the case relates and, to that end, to
adopt the arrangements proposed by the Parties. The Court visited the area
from 1to 4 April 1997; it visited a number of locations along the Danube and
took note of the technical explanations given by the representatives who had
been designated for the purpose by the Parties.
Il. The Court held a first round of ten public hearings from 3 to 7 March
and from 24 to 27 March 1997,and a second round of four public hearings on
10, 11, 14 and 15 April 1997,after having made the visit in situ referred to in
the previous paragraph. During those hearings, the Court heard the oral argu-
ments and replies of:

For Hungary: H.E. Mr. Szénasi,
Professor Valki,
Professor Kiss,
Professor Vida,
Professor Carbiener,
Professor Crawford,
Professor Nagy,
Dr. Kern,
Professor Wheater,

Ms Gorove.
Professor Dupuy,
Professor Sands.
For Slovakia: H.E. Dr. Tomka,
Dr. Mikulka,
Mr. Wordsworth,
Professor McCaffrey,
Professor Mucha,

Professor Pellet,
Mr. Refsgaard,
Sir Arthur Watts.
12. The Parties replied orally and in writing to various questions put by
Members of the Court. Referring to the provisions of Article 72 of theRules of
Court, each of the Parties submitted to the Courtits comments upon the replies

given by the other Party to some of those questions.Cour à se déplacersur les lieux auxquels se rapporte l'affaireày exercer ses
fonctions relativeà l'établissementdes preuves, conformément àl'article 66 du
Règlement.Pour sa part, l'agent de la Hongrie avait indiqué,par lettre en date

du 28 juin 1995, que, si la Cour jugeait une telle visite utile, son gouverne-
ment serait heureux de collaborer l'organisation de celle-ci.Par lettre du 14no-
vembre 1995, lesagents des Parties notifièrentconjointement àla Cour le texte
d'un protocole d'accor'd,conclu Budapest età New York le même jour, en vue
de proposer ila Cour les modalitésd'unetelledescentesur leslieux; et, par lettre
du 3 février 1997,ils lluinotifièrent conjointement le texte d'un procès-verbal
établià Budapest et 51New York le mêmejour, qui complétait le protocole
d'accord du 14novembre 1995. La Cour, par ordonnance en date du 5 février
1997,a décidéde donner suite àl'invitation qui lui était faited'exercer sesfonc-
tions relativesà l'étatilissementdes preuves sur les lieux auxquels l'affaire se
rapporte, et d'adopter à cette fin les modalités proposéespar les Parties. La
Cour s'est déplacéesur les lieux du 1" au 4 avril 1997; elle a visitéun certain
nombre de sites lelong du Danube et a pris note des explications techniques qui

lui ont étéfournies pa.r les représentants que les Parties avaient désigàécet
effet.
II. La Cour a tenu une première sériede dix audiences publiques du 3 au
7 mars et du 24 au 27 mars 1997; elle a tenu une seconde sériede quatre
audiences publiques les 10,1 1, 14 et 15avril 1997,après avoir effectuéla des-
cente sur leslieux dont ilest fait mention au paragraphe précédent.Au cours de
ces audiences ont été entendus enleurs plaidoiries et réponses:

Pour la Horigrie: S. Exc. M. Szénisi,
M. Valki,
M. Kiss,
M. Vida,
M. Carbiener,
M. Crawford,
M. Nagy,
M. Kern,
M. Wheater,

MmeGorove,
M. Dupuy,
M. Sands.
Pour lu Slovaquie: S. Exc. M. Tomka,
M. Mikulka,
M. Wordsworth,
M. McCaffrey,

M. Mucha,
M. Pellet,
M. Refsgaard,
sir Arthur Watts.

12. Les Parties ont répondu oralement et par écrit à diverses questions
poséespar des membres de la Cour. Se référantaux dispositions de l'article 72
du Règlement, chacune desParties a fait teniàla Cour des observations sur les
réponsesdonnéespal-l'autre Partie à certaines de ces questions.15 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

13. In the course of the written proceedings, the following submissions were
presented by the Parties:

On hekaif of Hungary,

in the Memorial, the Counter-Memorial and the Reply (mutatis mutandis iden-
ticai texts:

"On the basis of the evidence and legal argument presented in the
Memorial, Counter-Memorial and this Reply, the Republic of Hungary

Reyuests the Court to rrdjudgeand declare
First, that the Republic of Hungary was entitled to suspend and subse-
quently abandon the works on the Nagymaros Project and on the part of
the Gabtikovo Project for which the Treaty attributed responsibility to the
Republic of Hungary;
Second, that the Czech and Slovak Federal Republic was not entitled to
proceed to the 'provisional solution' (damming up of the Danube at river
kilometre 1851.7on Czechoslovak territory and resulting consequences on

water and navigation course);

Tizird, that by its Declaration of 19 May 1992, Hungary validly termi-
nated the Treaty on the Construction and Operation of the Gabtikovo-
Nagymaros Barrage System of 16 September 1977:

Rrqzre.~tsthe Court to adjzldgeand declarefurtller

that the legal consequences of these findings and of the evidence and the
arguments presented to the Court are as follows:

(1) that the Treaty of 16September 1977has never been in force between
the Republic of Hungary and the Slovak Republic;
(2) that the Slovak Republic bears responsibility to the Republic of Hun-
gary for maintaining in operationthe 'provisional solution' referred to
above ;
(3) that the Slovak Republic is internationally responsible for the damage
and loss suffered by the Republic of Hungary and by its nationals as a
result of the 'provisional solution';
(4) that the Slovak Republic is under an obligation to make reparation in
respect of such damage and loss, the amount of such reparation, if it
cannot be agreed by the Parties within six months of the date of the
Judgment of the Court,to be deterrnined by the Court;
(5) that the Slovak Republic is under the following obligations:

(a) to return the waters of the Danube to their course along the
international frontier between the Republic of Hungary and the
Slovak Republic, that is to Say the main navigable channel as
defined by applicable treaties;
(b) to restore the Danube to the situation it was in prior to the
putting into effect of the provisional solution: and
(c) to provide appropriate guarantees against the repetition of the
damage and loss suffered by the Republic of Hungary and by its
nationals." 13. Dans la procédure écrite,les conclusions ci-après ont étéprésentéespar
les Parties:

Au nom de lu Hongrie
dans le mémoire, le contre-mémoire et la réplique (textes identiques mutatis
mutartdis) :

<<Surla base des élémentsde preuve et des arguments juridiques pré-
sentés dans son mémoire, son contre-mémoire et sa réplique, la Répu-
blique de Hongrie

Prie lu Cour de dire et juger:

Prrmi2rement. que la République de Hongrieétait en droit de suspendre
puis d'abandonner les travaux relatifs au projet de Nagymaros ainsi qu'à
la partie du projei. de GabCikovo dont la République de Hongrie était res-
ponsable aux terrnes du traité;
Deu.uiémement.que la République fédérativetchèque et slovaque n'était
pas en droit de recourir à la ((solution provisoire)) (construction d'un bar-
rage sur le Danube au kilomètre 1851.7 du fleuve, en territoire tchécoslo-
vaque, et conséquencesen résultant pour l'écoulementdes eaux et la navi-
gation):
TroisiPt~~rtnent,que, par sa déclaration du 19 mai 1992, la Hongrie a
valablement mis fin au traité du 16 septembre 1977 relatif à la construc-
tion et au fonctionnement du système de barrage de GabCikovo-Nagy-

maros :
Prie lu Cour de dire et juger kgalement

que les conséquences juridiques de ces conclusions et des élémentsde
preuve et arguments présentés à la Cour sont les suivantes:
1) que le traité (lu 16 septembre 1977 n'a jamais étéen vigueur entre la
République de Hongrie et la République slovaque;
2) que la République slovaque est responsable envers la Hongrie pour
avoir poursuivi l'exploitation de la ((solution provisoire »:

3)rque la République slovaque est internationalement responsable des
dommages et pertes que la République de Hongrie et ses ressortissants
ont subis du iraitde la ((solutionprovisoire));
4) que la République slovaque est tenue de réparer ces dommages et ces
pertes, et qui: le montant de ladite réparation sera déterminépar la
Cour si les Parties ne peuvent en convenir entre elles dans les six mois
suivant la date à laquelle la Cour aura rendu son arrêt;
5) que la République slovaque est tenue des obligations suivantes:

tr) rétablir les eaux du Dariube dans leur cours le long de la frontiére
internationale entre la République de Hongrie et la République slo-
vaque, c'est-à-dire le principal chenal de navigation tel que défini
par les traités applicables:
h) rétablir la situation dans laquelle le Danube se trouvait avant la
mise en service de la solution provisoire;
c) fournir des garanties adéquates contre la répétition desdommages
et pertes subis par la République de Hongrie et par ses ressortis-
sants.))16 GABCIKOVO-NAGYMAROSPROJECT(JUDGMENT)

On behaif of Slovakia,
in the Memorial, the Counter-Memorial and the Reply (mutatis mutandis iden-

tical texts:
"On the basis of the evidence and legal arguments presented in the Slo-
vak Memorial, Counter-Memorial and in this Reply, and reserving the
right to supplement or amend its claims in the light of further written
pleadings, the Slovak Republic

Requests fhe Court to udjudge and declare:
1. That the Treaty between Czechoslovakia and Hungary of 16September
1977 concerning the construction and operation of the Gabtikovol
Nagymaros Systemof Locks, and related instruments, and to which the
Slovak Republic is the acknowledged successor, is a treaty in force and
has been so from the date of its conclusion; and that the notification of
termination by the Republic of Hungary on 19 May 1992was without
legal effect.
2. That the Republic of Hungary was not entitled to suspend and subse-

quently abandon the works on the Nagymaros Project and on that part
of the Gabtikovo Project for which the 1977Treaty attributed respon-
sibility to the Republic of Hungary.
3. That the act of proceeding with and putting into operation Variant C,
the 'provisional solution', was lawful.
4. That the Republic of Hungary must therefore cease forthwith al1con-
duct which impedes the full and bona fide implementation of the 1977
Treaty and must take al1 necessary steps to fulfil its own obligations
under the Treaty without further delay in order to restore compliance
with the Treaty.
5. That, in consequence of its breaches of the 1977Treaty, the Republic of
Hungary is liable to pay, and the Slovak Republic is entitled to receive,
full compensation for the loss and damage caused to the Slovak Repub-
lic by those breaches, plus interest and loss of profits, in the amounts
to be determined by the Court in a subsequentphase of the proceedings

in this case."
14. In the oral proceedings. the following submissions were presented by the
Parties

On behaif of Huagury,
at the hearing of 11 April 1997:

The submissions read at the hearing were mutatis mutandis identical to those
presented by Hungary during the written proceedings.
On behalf of'Slovakia,

at the hearing of 15April 1997 :
"On the basis of the evidence and legal arguments presented in its writ-
ten and oral pleadings, the Slovak Republic,

Requests the Court to adjudge and declare:
1. That the Treaty, as defined in the first paragraph of the Preamble to the
Compromis between the Parties, dated 7 April 1993, concerning the
construction and operation of the GabtikovolNagymaros System of
Locks and related instruments, concluded between Hungary and PROJET GABC~KOVO-NAGYMAROS (ARRÊT) 16

Au nom de la Slovaquie,
dans le mémoire,le contre-mémoire et la réplique(textes identiques mutatis
mutandis) :

«Sur la base des élémentsde preuve et des arguments juridiques pré-
sentésdans son mémoire,son contre-mémoireet sa réplique,et en se réser-
vant le droit de compléterou de modifier son argumentation a la lumière
d'autres exposés,la République slovaque

Prie lu Cour de dire etjuger:
1. Que le traitéclu 16septembre 1977entre la Hongrie et la Tchécoslova-
quie relatif la construction età l'exploitation du systèmed'éclusesde
GabCikovo-N.agymaros, et les instruments s'y rapportant, à l'égard
duquel il est reconnu que la République slovaqueest I'Etat successeur,
constitue un traité en vigueur et ce depuis la date de sa conclusion; et
que la notification de terminaison effectuéele 19mai 1992par la Répu-

blique de Hongrie est sans effetjuridique.
2. Que la République de Hongrie n'étaitpas en droit de suspendre puis
d'abandonner les travaux relatifs au projet de Nagymaros ainsi qu'à la
partie du projet de GabCikovo dont la Républiquede Hongrie est res-
ponsable aux termes du traitéde 1977.
3. Que le recours à la variante C. la «solution provisoire)), et sa mise en
service consti1:uaientun acte licite.
4. Que la Républiquede Hongrie doit dès lorsmettre immédiatement un
terme à toute conduite qui empêche l'application intégraleet de bonne
foi du traitéde 1977et doit prendre toutes les mesures nécessairespour
s'acquitter de:$obligations que lui impose ce traité sansplus tarder, afin
de faire en sorte que le traitésoit à nouveau respecté.

5. Qu'en conséquencede sa violation du traitéde 1977la République de
Hongrie doit payer, et la République slovaque a le droit de recevoir,
une indemnisation complète au titre des pertes et dommages occa-
sionnéspar ces violations àla République slovaque, y compris les inté-
rêtset la réparation du manque à gagner, dont le montant sera déter-
minépar la Cour lors d'une phase ultérieurede la présenteinstance.))
14. Dans la procédure orale, les conclusions ci-après ont été présentéepsar

les Parties:
Au nom de la Hongri:e.

à l'audience du I1 avril 1997:
Les conclusions lur:à I'audience étaientmutatis mutandis identiques Acelles
présentéespar la Hongrie dans la procédureécrite.

Au nom de lu Slovuquie,
à I'audience du 15a~~ril1997:

«Sur la base des élémentsde preuve et des arguments juridiques pré-
sentésdans ses écritureset ses plaidoiries orales, la République slovaque
Prie Iu Cour de bien vouloir dire et juger:

1. Que le traité, tel qu'il est défiài l'alinéapremier du préambule du
compromis entre les Parties endate du 7 avril 1993,relatiàla construc-
tion età l'exploitation du systèmed'éclusesde Gabtikovo-Nagymaros
et les instruments s'y rapportant, conclu entre la Hongrie et la Tché- Czechoslovakia and with regard to which the Slovak Republic is the
successor State, has never ceased to be in force and so remains, and
that the notification of 19 May 1992of purported termination of the
Treaty by the Republic of Hungary was without legal effect;
2. That the Republic of Hungary was not entitled to suspend and subse-
quently abandon theworks onthe Nagymaros Project and on that part
of the Gabeikovo Project for which the 1977Treaty attributes respon-
sibility to the Republic of Hungary;
3. That the Czech and Slovak Federal Republic was entitled,in Novem-
ber 1991,to proceed withthe 'provisionalsolution' and to put this sys-
tem into operation from October 1992;and that the Slovak Republic
was, and remains, entitled to continue the operation of this system;

4. That the Republic of Hungary shall therefore cease forthwith al1con-
duct which impedes the bona fide implementation of the 1977Treaty
and shall take al1necessarysteps to fulfilits own obligations under the

Treaty without further delay in order to restore compliance with the
Treaty, subject to any amendments which may be agreed between the
Parties;
5. That the Republic of Hungary shall giveappropriate guarantees that it
will not impede the performance of the Treaty, and the continued
operation of the system;
6. That, in consequenceof its breachesof the 1977Treaty, the Republicof
Hungary shall, in addition to immediately resumingperformance of its
Treaty obligations, pay to the Slovak Republic full compensation for
the lossand damage, including loss ofprofits, caused by those breaches
together with interest thereon;
7. That the Parties shall immediatelybegin negotiations with a view, in
particular, to adopting a new timetable and appropriate measures for
the implementation of the Treaty by both Parties, and to fixing the
amount of compensation due by the Republic of Hungary to the Slo-
vak Republic; and that. if the Parties are unable to reach an agreement
within six months, either one of them may request the Court to render
an additional Judgment to determine the modalities for executing its
Judgment."

15. The present case arose out ofthe signature, on 16 September 1977,
by the Hungarian People's Republic and the Czechoslovak People's
Republic, of a treaty "concerning the construction and operation of the
GabEikovo-Nagymaros System of Locks" (hereinafter called the "1977

Treatv"). The names of the two contractine States have varied over the
yearst hereinafter they will be referred touas Hungary and Czechoslo-
vakia. The 1977 Treaty entered into force on 30 June 1978.
It provides forthe construction and operation of a System of Locks by
the parties as a "joint investment". According to its Preamble, the bar-
rage system was designed to attain

"the broad utilization of the natural resources of the Bratislava-
Budapest section of the Danube river for the development of water PROJET GABCIKOVO-NAGYMAROS (ARRÊT) 17

coslovaquie,à l'égardduquel la République slovaque est1'Etatsucces-
seur, n'a jamaiscesséd'êtreen vigueur et le demeure, et que la notifica-
tion, le 19 mai 1992, de la prétendue terminaison du traité par la
République de Hongrie n'a eu aucuneffet sur la validité decelui-ci;

2. Que la Républiquede Hongrie n'était pas endroit de suspendre puis
d'abandonner les travaux relatifs au projet de Nagymaros ainsi qu'à la
partie du projet de GabCikovodont la Républiquede Hongrie est res-
ponsable aux termes du traité;
3. Que la République fédérative tchèque et slovaque était en droit de
recourir. en novembre 1991, à la «solution provisoire))et de mettre ce
systèmeen service à partir d'octobre 1992et que la Républiqueslo-
vaque étaitet ,demeureen droit de continuer a mettre en Œuvrece sys-
tème ;
4. Que la Républliquede Hongrie doit dés lors mettre immédiatemenutn
terme à toute conduite qui empêchel'application de bonnefoi du traité
de 1977 et qu'elle doit prendre toutes les mesures nécessairespour
s'acquitter sansretard des obligations que lui impose ce traité,afin de
faire en sorte que letraité àonouveau respecté,sousréserve desmodi-
fications qui pourraient y être apportésar accord entre les Parties;

5. Que la Républiquede Hongrie doit donner des garanties adéquatesde
s'abstenird'eimpêcherl'application du traité et le fonctionnement
continu du syc,t'me;
6. Qu'en conséqiience desa violation du traitéde 1977,la Républiquede
Hongrie doit, outre la reprise immédiatede l'exécution deses obliga-
tions en vertu du traité,payeà la Républiqueslovaque une indemnisa-
tion compléteau titre des pertes et dommages, y compris le manque à
gagner, occasionnéspar ces violations, assortis des intérêts;
7. Que les Parties doivent engager immédiatement des négociations en
vue, notamment, de l'adoption d'un nouveau calendrieret de mesures
appropriéespour la mise en Œuvredu traité par les deux Parties et la
fixation du montant de l'indemnitédue par la Républiquede Hongrie à
la République slovaque;et que si lesParties ne peuvent parvenir à un
accord dans un délaide six mois, l'une ou l'autre d'entre elles pourra
prier la Cour de rendre un arrêtsupplémentairepour déterminerles

modalitésd7e:cécution de son arrêt))

15. La présente affaire trouve son origine dans la signature, le 16 sep-
tembre 1977, par la République populaire hongroise et la République
socialiste tchécoslovaque d'un traité ((relatif à la construction et au fonc-

tionnement du systéme d'éclusesde Gabcikovo-Nagymaros* (dénommé
ci-après le ((traitéde 1977))). Le nom des deux Etats contractants a varié
au cours des ans; ils seront dénommés ci-après la Hongrie et la Tchéco-
slovaquie. Le traité de 1977 est entré en vigueur le 30 juin 1978.
Il prévoit la construction et l'exploitation du système d'éclusespar les

parties «en tant qu'investissement conjoint)). Selon le préambule du
traité, le système de:barrage avait pour but
((de mettre en valeur, de façon générale,les ressources naturelles de

la section Bratislava-Budapest du Danube aux fins du développe- GABC~KOVO-NAGYMAROSPROJECT (JUDGMENT)

resources, energy, transport, agriculture and other sectors of the
national economy of the Contracting Parties".

The joint investment was thus essentially aimed at the production of
hydroelectricity, the improvement of navigation on the relevant sec-
tion of the Danube and the protection of the areas along the banks
against flooding. At the same time, by the terms of the Treaty, the con-
tracting parties undertook to ensure that the quality of water in the Dan-
ube was not impaired as a result of the Project, and that compliance with

the obligations for the protection of nature arising in connection with the
construction and operation of the System of Locks would be observed.
16. The Danube is the second longest river in Europe, flowingalong or
across the borders of nine countries in its 2,860-kilometre course from the
Black Forest eastwards to the Black Sea. For 142kilometres, it formsthe
boundary between Slovakia and Hungary. The sector with which this
case is concerned is a stretch of approximately 200 kilometres, between
Bratislava in Slovakia and Budapest in Hungary. Below Bratislava, the
river gradient decreases markedly, creating an alluvial plain ofrave1and
sand sediment. This plain is delimited to the north-east, in Slovak terri-
tory, by the Maly Danube and to the south-west, in Hungarian territory,
by the Mosoni Danube. The boundary between the two States is consti-
tuted, in the major part of that region, by the main channel of the river.
The area lying between the Mali Danube and that channel, in Slovak
territory, constitutes theitni Ostrov; the area between the main chan-
ne1 and the Mosoni Danube, in Hungarian territory, constitutes the.
Szigetkoz. Cunovo and, further downstream, GabCikovo, are situated in
this sector of the river on Slovak territory, Cunovo on the right bank and
GabCikovo on the left. Further downstream, after the confluence of the
various branches, the river enters Hungarian territory and the topo-

graphy becomes hillier. Nagymaros lies in a narrow valleyat a bend in the
Danube just before it turns south, enclosing the large river island of Szen-
tendre before reaching Budapest (see sketch-map No. 1, p. 19below).

17. The Danube has always played a vital part in the commercial and
economic development of its riparian States, and has underlined and
reinforced their interdependence, making international CO-operation
essential. Improvements to the navigation channel have enabled the Dan-
ube, now linked by canal to the Main and thence to the Rhine, to become
an important navigational artery connecting the North Sea to the Black
Sea. In the stretch of river to which the case relates, flood protection
measures have been constructed over the centuries, farming and forestry
practised, and, more recently, there has been an increase in population
and industrial activity in therea. The cumulative effects on the river and
on the environment of various human activities over the years have not
al1been favourable, particularly for the water régime. PROJET GABCIKOVO-NAGYMAROS (ARRÉT) 18

ment des secteurs des ressources hydrauliques, de l'énergie, des
transports et de l'agriculture et des autres secteurs de l'économie
nationale des parties contractantes)).

L'investissement conjoint tendait ainsi essentiellement à la production
d'hydro-électricité,à l'amélioration dela navigation sur le tronçon en
cause du Danube et ila protection des régions riverainescontre les inon-
dations. En mêmetemps, les parties contractantes, selon les termes du
traité,s'engageaient tant à veilleà ce que la mise en Œuvredu projet ne
compromette pas la qualitédes eaux du Danube qu'à s'acquitter de leurs

obligationsconcernaritlaprotection delanature et découlant delaconstruc-
tion et du fonctionni:ment du système d'écluses.
16. Par sa longueur, le Danube est le deuxièmefleuve d'Europe, lon-
geant ou traversant neuf pays sur un cours de 2860 kilomètres et se diri-
geant vers l'est,depuis la Forêt-Noirejusqu'à la mer Noire. Sur 142kilo-
mètres, il constituela frontière entre la Slovaquie et la Hongrie. Le sec-
teur auquel se rapporte la présente affaire est un tronçon d'environ
200 kilomètres, entre:Bratislava, en Slovaquie, et Budapest, en Hongrie.
En aval de Bratislava, la déclivitdu fleuve diminue sensiblement, créant
une plaine alluviale de gravier et de sédiments sableux. Cette plaine est
délimitéeau nord-est, en territoire slovaque, par le petit Danube et au
sud-ouest, en territoire hongrois, par le bras Moson du Danube. La fron-
tière entre les deux Etats est constituée dans la ma-jeurepartie de cette
régionpar le chenal principal du fleuve. La zone c6mprisewentrele petit

Danube et ce chenal constitue, en territoire slovaque, le Zitny Ostrov;
cellecomprise entre le chenal principal ete bras Moson du Danube cons-
titue, en territoire hongrois, le Szigetkoz. Cunovo et, plus ena1,"GabCi-
kovo sont situésdans ce secteur du fleuve,en territoire slovaque;Cunovo
est situé sur la rive droite du fleuve et GabCikovo sur la rive gauche.
Plus bas, aprèsjonction des divers bras, le fleuveentre en territoire hon-
grois et le relief devient plus accidenté. Nagymaros se trouve dans
une valléeétroite à uinendroit où le Danube fait un coude juste avant de
se diriger vers le sud..entourant la grande île fluvialede Szentendre avant
d'atteindre Budapest. (voir ci-après, p. 19, le croquis 1).
17. Le Danube a toujours joué un rôle vital dans le développement
commercial et éconcimiquedes Etats riverains; il a mis en évidenceet a
accru leur interdépendance, rendant indispensable la coopération inter-
nationale. Des améliorations apportéesau chenal de navigation ont per-

mis au Danube, aujourd'hui reliépar un canal au Main et de là au Rhin,
de devenir une importante artère de navigation reliant la mer du Nord à
la mer Noire. Dans le tronçon du fleuve auquel se rapporte la présente
affaire, des mesures de protection contre les inondations ont étéprises au
cours des siècles,1'ag:ricultureet la sylviculture ont étépratiquées et,plus
récemment,la régiona connu un essor démographique et industriel. Les
effets cumulatifs, sur le fleuve et l'environnement, des diverses activités
humaines menéesau cours des ans n'ont pas tous étépositifs, notamment
en ce qui concerne II:régime deseaux.20 GABCIKOVO-NAGYM PAORJCT (JUDGMENT)

Only by international CO-operation could action be taken to alleviate
these problems. Water management projects along the Danube have fre-
quently sought to combine navigational improvements and flood protec-
tion with the production of electricity through hydroelectric power plants.
The potential of the Danube for the production of hydroelectric power
has been extensively exploited by some riparian States. The history of
attempts to harness the potential of the particular stretch of the river at
issue inthese proceedings extends over a 25-year period culminating in
the signature of the 1977Treaty.

18. Article1, paragraph 1, of the 1977Treaty describes the principal
works to be constructed in pursuance of the Project. It provided for the
building of two series of locks, one at Gabëikovo (in Czechoslovak ter-

ritory) and the other at Nagymaros (in Hungarian territory), to consti-
tute "a single and indivisible operational system of works" (see sketch-
map No. 2, p. 21 below). The Court will subsequently have occasion to
revert in more detail to those works, which were to comprise,interalia, a
reservoir upstream of Dunakiliti, in Hungarian and Czechoslovak terri-
tory; a dam at Dunakiliti, in Hungarian territory; a bypass canal, in
Czechoslovak territory, on which was to be constructed the Gabcikovo
System of Locks (together with a hydroelectric power plant with an
installed capacity of 720 megawatts (MW)); the deepening of the bed of
the Danube downstream of the place at which the bypass canal was to
rejoin the old bed of the river; a reinforcement of flood-control works
along the Danube upstream of Nagymaros; the Nagymaros System of
Locks, in Hungarian territory (with a hydroelectric power plant of a
capacity of 158MW); and the deepening of the bed of the Danube down-

Stream.
Article 1, paragraph 4, of the Treaty further provided that the techni-
cal specifications concerning the system would be included in the "Joint
Contractual Plan" which was to be drawn up in accordance with the
Agreement signed by the two Governments for this purpose on 6 May
1976;Article 4, paragraph 1, for its part, specifiedthat "the joint invest-
ment [would] be carried out in conformity with the joint contractual
plan".
According to Article 3, paragraph 1 :

"Operations connected with the realization of the joint investment
and with the performance of tasks relating to the operation of the
System of Locks shall be directed and supervised by the Govern-
ments of the Contracting Parties through . . .(. . .'government
delegates')."

Those delegates had, interalia, "to ensure that construction of the Sys-
tem of Locks is . . .carried out in accordance with the approved joint
contractual plan and the project work schedule". When the works were
brought into operation, they were moreover "To establish the operating PROJET GABCIKOVO-NAGYMAROS (ARRÊT) 20

Des mesures destinées à atténuer ces problèmes ne pouvaient être
prises que dans le cadre d'une coopération internationale. Les projets de
gestion des eaux du Danube ont souvent cherché a combiner améliora-
tion des conditions de navigation, lutte contre les inondations et produc-
tion d'électricitépar des centrales hydro-électriques. Certains Etats rive-

rains ont largement tiré parti des ressources du Danube en matière de
production d'énergiehydro-électrique. Les tentatives qui ont été faites
pour exploiter le potentiel du tronçon particulier du fleuve qui est en
cause dans la présenteinstance se sont échelonnéessur une période de
vingt-cinq ans, qui a culminé avecla signature du traité de 1977.
18. Les principaux ouvrages à construire en exécutiondu projet sont
décritsau paragraphlr 1de l'article premierdu traitéde 1977.Deux séries
d'éclusesétaient prkvues, l'une à Gabeikovo (en territoire tchécoslo-
vaque), l'autre à Nagymaros (en territoire hongrois), en vue de consti-
tuer «un systèmed'ouvrages opérationnel, unique et indivisible >)(voir ci-
après,p. 21, lecroquis no 2). La Cour aura plus loin l'occasion de revenir
sur le détail de ces ouvrages, qui devaient notamment comprendre un

réservoir enamont de Dunakiliti, en territoire hongrois et en territoire
tchécoslovaque; un barrage à Dunakiliti, en territoire hongrois; un canal
de dérivation,en territoire tchécoslovaque, surlequel devait être construit
le système d'éclusesde Gablikovo (de mêmequ'une centrale hydro-
électriqued'une capacitéinstalléede 720 mégawatts(MW)); l'approfon-
dissement du lit du Danube après lajonction du canal de dérivationet de
l'ancien litdu fleuve; un renforcement des ouvrages de protection contre
les inondations le long du Danube en amont de Nagymaros; le système
d'éclusesde Nagyma~ros,en territoire hongrois (avec une centrale hydro-
électriqued'une capacitéde 158 MW); et l'approfondissement du lit du
Danube en aval.
Le paragraphe 4 de l'article premier du traitéprévoyait que les spéci-

fications techniques concernant le systèmeseraient fixéesdans le «plan
contractuel conjoint)), qui devait être établi conformément à l'accord
signé à cette fin par les deux gouvernements le 6 mai 1976; le para-
graphe 1de l'article 4 précisaitquantà lui que «l'investissement conjoint
[serait] effectuéconformément au plan contractuel conjoint ».

Aux termes du paragraphe 1 de l'article 3:

«Les opérations liées à la réalisationde l'investissement conjoint
et à l'exécution destâches relatives au fonctionnement du système
d'écluses seront. dirigées et superviséepsar les gouvernements des
parties contractantes, par l'intermédiaire de .. ( ..((déléguég sou-

vernementaux))). ))

Ces déléguéé staientnotamment chargés de«veiller à ce que la construc-
tion du système d'écluses soit ..réaliséeconformément au plan contrac-
tuel conjoint approuvéet au calendrier des travaux du projet ».Lors de la
mise en service des ouvrages, ils devaient en outre ((établirles procédures Bratislava

Slovakia

/

\

Komarom

Szentendre
Island

SKETCH-MAPNO.2 Hungary
The OriginalProject

N.B.: This sketch-maphas
beenpreparedfor illustrative
purposesonly

Sketch-mapnotoscale II Bratislava

-s +fi..
: -(\ iitng ~strov~~~ Slovaquie

Ilede
Szentendre

CROQUISNo 2 Hongrie
Projoriginal

N.B.:Cecroquétablié
àdes finspurementillustratives

Croauià l'échelle and operational procedures of the System of Locks and ensure compli-
ance therewith."
Article 4, paragraph 4, stipulated that:
"Operations relating to the joint investment [should] be organized
by the Contracting Parties in such a way that the power generation
plants [would] be put into service during the period 1986-1990."

Article 5 provided that the cost of the joint investment would be borne
by the contracting parties in equal measure. It specified the work to be
carried out by each one of them. Article 8 further stipulated that the
Dunakiliti dam, the bypass canal and the two series of locks at Gab-
Cikovo and Nagymaros would be "jointly owned" by the contracting
parties "in equal measure". Ownership of the other works was to be
vested in the State on whose territory they were constructed.
The parties were likewiseto participate in equal measure in the use of
the system put in place, and more particularly in the use of the base-load
and peak-load power generated at ,the hydroelectric power plants
(Art. 9).

According to Article 10,the works were to be managed by the State on
whose territory they were located, "in accordance with the jointly-agreed
operating and operational procedures", while Article 12 stipulated that
the operation, maintenance (repair) and reconstruction costs of jointly
-owned works of the System of Locks were also to be borne jointly by the
contracting parties in equal measure.

According to Article 14,
"The discharge specified in the water balance of the approved
joint contractual plan shall be ensured in the bed of the Danube
[between Dunakiliti and Sap] unless natural conditions or other cir-

cumstances temporarily require a greater or smaller discharge."

Paragraph 3 of that Article was worded as follows:

"In the event that the withdrawal of water in the Hungarian-
Czechoslovak section of the Danube exceeds the quantities of water
specified in the water balance of the approved joint contractual plan
and the excess withdrawal results in a decrease in the output of
electric power, the share of electric power of the Contracting Party
benefiting from the excess withdrawal shall be correspondingly
reduced."
Article 15specified that the contracting parties

"shall ensure, by the means specified in the joint contractual plan,
that the quality of the water in the Danube is not impaired as a
result of the construction and operation of the System of Locks". PROJET GABCIKOVO-NAGYMAROS (ARRET) 22

opérationnelles concernant le système d'écluses et enassurer I'observa-
tion».
Le paragraphe 4 de l'article 4 stipulait que:

«Les opérati,onsliées à l'investissement conjoint ser[aient] orga-
niséespar les parties contractantes de façon que les centrales de
générationd'énergie soient misesen service pendant la période 1986-
1990.))

L'article 5 disposait que les coûts de l'investissement conjoint seraient
pris en charge, à parts égales,par les parties contractantes. Il précisait
les travaux à réaliserpar chacune d'entre elles. L'article 8 ajoutait que le
barrage de Dunakiliti, le canal de dérivation et les deux séries d'écluses
de GabEikovo et hlagymaros seraient ((la propriété conjointe, à parts
égales)),des parties contractantes. Lesautres ouvrages devaient êtrela pro-
priétéde 1'Etatsur Ileterritoire duquel ils étaientconstruits.
Les parties devaient de mêmeparticiper à parts égalesà l'utilisation du
système mis en placeet plus particuliérement à l'utilisation de l'énergiede
base et de pointe généréd eans les centrales hydro-électriques(art. 9).

Aux termes de l'article 10, les ouvrages devaient êtregéréspar I'Etat
sur le territoire duquel ils se trouvaient, ((conformément aux procédures
opérationnelles arrêtéeds'un commun accord)),alors que I'article 12pré-
voyait que les frais d'exploitation, d'entretien (réparation) et de recons-
truction des ouvrages du système d'éclusesappartenant en commun aux
parties contractantes seraient aussi pris en charge conjointement,à parts
égales,par celles-ci.
Conformément à l'article 1:

«Le débitspécifié dans l'équilibrehydraulique prévudans le plan
contractuel conjoint approuvé sera assuré dans le lit du Danube
[entreDunakili.ti et Sap],à moins que des conditions naturelles ou
d'autres circonstances n'exigent temporairement un débit supérieur
ou inférieur.)

Le paragraphe 3 de cet article était ainsi libellé:
«Au cas où les prélèvementsd'eau du Danube, dans le secteur
hungaro-tchécoslovaque, dépasseraientles quantitésd'eau spécifiées
dans l'équilibre:hydraulique prévudans le plan contractuel conjoint
approuvé et où les prélèvementsentraîneraient une diminution de la
production d'énergie électrique, lapart d'énergieélectrique revenant

à la partie contractante ayant procédéaux prélèvements excéden-
taires sera réduiteen conséquence. »
L'article 15précisaitque les parties contractantes

«veiller[aient], selon les modalitésspécifiésans le plan contractuel
conjoint, à ce que la qualitédes eaux du Danube ne soit pas com-
promise par suite de la construction et du fonctionnement du sys-
tème d'écluses>>. Article 16 set forth the obligations of the contracting parties concern-
ing the maintenance of the bed of the Danube.
Article 18, paragraph 1, provided as follows :
"The Contracting Parties, in conformity with the obligations pre-

viously assumed by them, and in particular with article 3 of the Con-
vention concerning the regime of navigation on the Danube, signed
at Belgrade on 18August 1948, shall ensure uninterrupted and safe
navigation on the international fairway both during the construction
and during the operation of the System of Locks."

It was stipulated in Article 19 that:

"The Contracting Parties shall, through the means specifiedin the
joint contractual plan, ensure compliance with the obligations for
the protection of nature arising in connection with the construction
and operation of the System of Locks."

Article 20 provided for the contracting parties to take appropriate
measures, within the framework of their national investments, for the
protection of fishing interests in conformity with the Convention con-
cerning Fishing in the Waters of the Danube, signed at Bucharest on
29 January 1958.
According to Article 22, paragraph 1, of the Treaty, the contracting
parties had, in connection with the construction and operation of the
System of Locks, agreed on minor revision to the course of the State
frontier between them as follows:

"(d) In the Dunakiliti-HruSov head-water area, the State frontier
shall run from boundary point 161.V.O.A.to boundary stone
No. 1.5. in a straight line in such a way that the territories
affected, to the extent of about 10-10hectares shall be offset
between the two States."
It was further provided, in paragraph 2, that the revision of the State

frontier and the exchange of territories so provided for should be effected
"by the Contracting Parties on the basis of a separate treaty". No such
treaty was concluded.
Finally a dispute settlement provision was contained in Article 27,
worded as follows:
"1. The settlement of disputes in matters relating to the realiza-
tion and operation of the System of Locks shall be a function of the
government delegates.

2. If the government delegates are unable to reach agreement on
the matters in dispute, they shall refer them to the Governments of
the Contracting Parties for decision."
19. The Joint Contractual Plan, referred to in the previous paragraph,
set forth, on a large number of points, both the objectives of the system PROJET GABCIKOVO-NAGYMAROS (ARRÉT) 23

L'article 16indiquait quelles étaientles obligations des parties contrac-
tantes en ce qui concerne l'entretien du lit du Danube.
Quant à l'article 18, ilprévoyait ce qui suit en son paragraphe 1 :

«Les parties contractantes, conformément aux obligations qu'elles
ont précédemment assumées eten particulier à l'article 3 de la
convention relative au régimede la navigation sur le Danube signée

à Belgrade le 18août 1948,veilleront à ce que la navigation puisse se
poursuivre de f,açonininterrompue et dans des conditions de sécurité
dans le chenal international, tant pendant la construction que pen-
dant le fonctioi~nement du système d'écluses .

L'article 19 stipulai:

«Les parties contractantes assureront, par les moyens spécifiés
dans le plan cclntractuel conjoint, le respect des obligations concer-
nant la protection de la nature découlant de la construction et du
fonctionnement du système d'écluses. »

L'article 20 disposait que, dans le cadre de leurs investissements natio-
naux, les parties cointractantes prendraient les mesures appropriées pour
protéger les intérêts, enmatière de pêcheconformément a la convention
relative a la pêche(Jans le Danube, signéeà Bucarest le 29 janvier 1958.

Aux termes du paragraphe 1 de l'article 22 du traité,les parties contrac-
tantes étaientconvenues, dans le contexte de la construction et du fonction-
nement du système d'éclusesd ,'apporter des modifications mineuresau tracé
de la frontière d'Etat qui les sépare;ces modifications étaientles suivantes:

cd) Dans le secteur d'amont de Dunakiliti-HruSov, la frontière
d'Etat ira. du point frontière 161.V.0.i. à la borne frontière
no 1.5.,en ligne droite, de façon que les territoires affectés, à
concurrerice d'environ 10-10hectares, soient répartiségalement

entre les deux Etats. >)
II était en outre disposé,au paragraphe 2, que la revision de la frontière

d'Etat et l'échangede territoires ainsi prévus seraient effectués «par les
parties contractantes sur la base d'un traitédistinct ». Un tel traitén'a pas
été conclu.
Enfin, I'article 27 contenait des dispositions relatives au règlement des
différends, rédigéescomme suit :

«1. Le règlement des différends concernant toutes questions rela-
tives à la réalisation et au fonctionnement du système d'écluses
incombera aux.déléguég souvernementaux.
2. Si les déléguésgouvernementaux ne peuvent parvenir à un

accord sur les questions en litige, ils les soumettront aux gouverne-
ments des parties contractantes pour décisions. »

19. Sur un grand nombre de points, le plan contractuel conjoint men-
tionnéau paragraphe précédentprécisaità la fois les objectifs du systèmeand the characteristics of the works. In its latest version it specified in
paragraph 6.2 that the GabCikovo bypass canal would have a discharge
capacity of 4,000 cubic metres per second (m3/s).The power plant would
include "Eight . . .turbines with 9.20 m diameter running wheels" and
would "mainly operate in peak-load time and continuously during high
water". This type of operation would give an energy production of
2,650 gigawattihours (GWh) per annum. The Plan further stipulated in
paragraph 4.4.2 :
"The low waters are stored every day, which ensures the peak-

load time operation of the GabEikovo hydropower plant ... a mini-
mum of 50 m3/sadditional water is provided for the old bed [of the
Danube] besides the water supply of the branch system."
The Plan further specifiedthat, in the event that the discharge into the
bypass canal exceeded 4,000-4,500 m3/s, the excess amounts of water
would be channelled into the old bed. Lastly, according to paragraph 7.7
of the Plan:

"The common operational regulation stipulatesthat concerning the
operation of the Dunakiliti barrage in the event of needduring the
growing season 200m3/sdischarge mustbe releasedinto the old Dan-
ube bed, in addition to the occasionalpossibilitiesfor rinsingthe bed."

The Joint Contractual Plan alsocontained "Preliminary Operating and
Maintenance Rules", Article 23 of which specified that "The final oper-
ating rules [should] be approved within a year of the setting into opera-
tion of the system." (Joint Contractual Plan, Summary Documentation,
Vol. 0-1-A.)
Nagymaros, with six turbines, was, according to paragraph 6.3 of
the Plan, to be a "hydropower station . . type of a basic power-station
capable of operating in peak-load time for five hours at the discharge
interval between 1,000-2,500m3/s"per day. The intended annual produc-
tion was to be 1,025GWh (Le.,38per cent of the production of GabEikovo,
for an installed power only equal to 21 per cent of that of GabCikovo).

20. Thus, the Project was to have taken the form of an integrated joint
project with the two contracting parties on an equal footing in respect of
the financing, construction and operation of the works. Its single and
indivisible nature was to have been realized through the Joint Contrac-
tua1Plan which complemented the Treaty. In particular, Hungary would
have had control of the sluices at Dunakiliti and the works at Nagy-
maros, whereas Czechoslovakia would have had control of the works at
GabCikovo.

21. The schedule of work had for its part been fixed inan Agreement
on mutual assistance signed by the two parties on 16 September 1977,at PROJET GABCIKOVO-NAGYMAROS (ARRÊT) 24

et les caractéristiques des ouvrages. Dans sa dernière version, il spécifiait

en son paragraphe 6.2 que le canal de dérivation de GabEikovo aurait
une capacité de débit de 4000 mètres cubes par seconde (m3/s). La cen-
trale compterait «huit turbines ...avec des aubes de 9,20 mètres de dia-
mètre)) et «fonctioi~ner[ait] principalement en régime de pointe et en
mode continu lors des hautes eaux)). Ce type de fonctionnement permet-

trait une production d'énergieélectriquede 2650 gigawattslheure (GWh)
par an. Le plan ajoutait en son paragraphe 4.4.2:

«Les basses eaux sont emmagasinéeschaque jour pour permettre le
fonctionnement en régimede pointe de la centrale hydro-électrique de
GabEikovo ...tandis qu'un débit minimum de 50 m3/s est assuré à
l'ancien lit [du Danube] en sus de l'eau fournie au système de bras.))

Le plan spécifiait enoutre que, dans les cas où le débitdans le canal de
dérivation dépasserait 4000-4500 m3is, les quantités d'eau excédentaires
seraient déverséesdans I'ancien lit. Enfin, selon le paragraphe 7.7 du

plan :
«Le règlement opérationnel conjoint prévoit qu'en cas de besoin

pendant la saison végétativele barrage de Dunakiliti devra envoyer
200 m3is dans I'ancien lit du Danube en sus des volumes occasion-
nellement nécessaires pour le rinçage du lit.))

Le plan contractuel conjoint comprenait également des ((consignes
provisoires d'exploitation et d'entretien)) dont l'article 23 précisaitque:
«Les consignes d7ex.ploitation définitives [seraient] agréées dans un délai
d'un an à compter de la mise en service du système.)) (Plan contractuel

coni.?,t. documentration de svnthèse. vol. 0-1-A.)
Quant à Nagyrna.ros, aveciix turbines, il devait s'agir, selon le para-
graphe 6.3 du plan, d'une ((centrale hydro-électrique ...du type centrale
de base capable de fonctionner en régimede pointe pendant cinq heures
avec un débit situéentre 1000 et 2500 m3/s» par jour. La production

annuelle prévue étaitde 1025 GWh (soit trente-huit pour cent de la pro-
duction de GabEikovo pour une puissance installéen'atteignant que vingt
et un pour cent de lrellede GabEikovo).
20. Ainsi, le projet devait se présenter comme un projet conjoint inté-
grédans lequel les deux parties contractantes seraient sur un pied d'éga-

litéen ce qui concerne le financement, la construction et l'exploitation
des ouvrages. Son caractère unique et indivisible devait êtreconcrétisé
grâce au plan contractuel conjoint qui complétait le traité. C'est sous le
contrôle de la Hongrie, en particulier, que se seraient trouvés les vannes
de Dunakiliti et les ouvrages de Nagymaros, tandis que les ouvrages de

GabEikovo aurait étéplacéssous le contrôle de la Tchécoslovaquie.

21. Le calendrier de réalisation des travaux avait pour sa part été fixé

dans un accord d'assistance mutuelle signépar les deux parties le 16 sep-25 GABCIKOVO-NAGYM RROJCT (JUDGMENT)

the same time as the Treaty itself. The Agreement moreover made some
adjustments to the allocation of the works between the parties as laid

down by the Treaty.
Work on the Project started in 1978.On Hungary's initiative, the two
parties first agreed, by two Protocols signed on 10 October 1983 (one
amending Article 4,paragraph 4,of the 1977 Treaty and the other the
Agreement on mutual assistance), to slow the work down and to post-
pone putting into operation the power plants, and then, by a Protocol

signed on 6 February 1989 (which amended the Agreement on mutual
assistance), to accelerate the Project.
22. As a result of intense criticism which the Project had generated in
Hungary, the Hungarian Government decided on 13 May 1989 to sus-
pend the works at Nagymaros pending the completion of various studies

which the competent authorities were to finish before 31 July 1989. On
21 July 1989,the Hungarian Government extended the suspension of the
works at Nagymaros until 31 October 1989,and, in addition, suspended
the works at Dunakiliti until theame date. Lastly, on 27 October 1989,
Hungary decided to abandon the works at Nagymaros and to maintain
the status quo at Dunakiliti.

23. During this period, negotiations were being held between the
parties. Czechoslovakia also started investigating alternative solutions.
One of them, subsequently known as "Variant CM,entailed a unilateral
diversion of the Danube by Czechoslovakia on its territory some 10kilo-
metres upstream of Dunakiliti (see sketch-map Nol 3, p. 26 below). In its

final stage, Variant C included the construction at Cunovo of an overflow
dam and a levee linking that dam to the south bank of the bypass canal.
The corresponding reservoir was to have a smaller surface area andro-
vide approximately 30 per cent less storage than the reservoir initially
contemplated. Provision was made for ancillary works, namely: an intake
structure to supply the Mosoni Danube; a weir to enable, interdia,

floodwater to be directed along the old bed of the Danube: an auxiliary
shiplock; and two hydroelectric power plants (one capable of an aniiual
production of 4 GWh on the Mosoni Danube, and the other with a pro-
duction of 174GWh on the old bed of the Danube). The supply of water
to the side-arms of the Danube on the Czechoslovak bank was to be

secured by means of two intake structures in the bypass canal at
DobrohoSt' and GabEikovo. A solution was to be found for the Hungar-
ian bank. Moreover, the question of the deepening of the bed of the Dan-
ube at the confluence of the bypass canal and the old bed of the river
remained outstanding.

On 23 July 1991, the Slovak Government decided "to begin, in Sep-
tember 1991, construction to put the GabEikovo Project into operation
by the provisional solution". That decision was endorsed by the Federal
Czechoslovak Government on 25 July. Work on Variant C began
in November 1991. Discussions continued between the two parties but to

no avail, and, on 19 May 1992, the Hungarian Government transmitted PROJET GABC~KOVO-NAGYM (ARROEST) 25

tembre 1977, en mêmetemps que le traité lui-même. L'accordapportait
par ailleurs quelques retouches à la répartition des travaux entre les
parties telle qu'opéréepar le traité.
Les travaux relatifs au projet commencèrent en 1978. A l'initiative de
la Hongrie, les deux parties convinrent d'abord, par deux protocoles
signésle 10octobre 1983(l'un amendant le paragraphe 4de l'articl4 du

traitéde 1977et l'autre l'accord d'assistance mutuelle), de ralentir les tra-
vaux et de différerla mise en service des centrales, puis, par un protocole
signé le 6 février 1989 (qui amendait l'accord d'assistance mutuelle),
d'accélérerle projet.
22. A la suite de vives critiques que le projet avait suscitéesen Hon-
grie, le Gouvernement hongrois décida le 13 mai 1989 de suspendre les

travaux à Nagymar,os en attendant l'achèvement de diverses études que
les autorités compétentesdevaient mener à bien avant le 3l juillet 1989. Le
21juillet 1989,le Gouvernement hongrois prolongea jusqu'au 31 octobre
1989 la suspension des travaux à Nagymaros et suspendit en outre les tra-
vaux à Dunakiliti jusqu'à la mêmedate. Enfin, le 27 octobre 1989, la
Hongrie décidad'abandonner les travaux à Nagymaros et de maintenir le

statu quo à Dunakiliti.
23. Au cours de cette période, des négociations furent tenues entre les
parties. La Tchécoslovaquie mit aussi à l'étudedes solutions de rechange.
L'une d'entre elles, dénommée par la suite ((variante CD, impliquait le
détournement unilai.éraldu Danube par la Tchécoslovaquie sur son ter-
ritoire à quelque 10 kilomètres en amont de Dunakiliti (voir ci-après,

p. 26. le croquisyno 3). Dans son dernier état. la variCncomportait la
construction à Cunovo d'un barrage déversoir et d'une digue reliant ce
barrage à la rive sud du canal de dérivation. Le réservoircorrespondant
devait avoir unesurface plus réduiteet disposer d'une capacitéde retenue
d'environ trente pour cent inférieure à celle du réservoir initialement
envisagé. Des ouvrages accessoires étaient prévus, à savoir: une prise
d'eau destinéeà alimenter le bras Moson du Danube; un déversoir per-

mettant, notamment, de diriger les eaux de crue dans l'ancien lit du
Danube; une éclusede navigation auxiliaire; et deux centrales hydro-
électriques (l'une permettant une production annuelle de 4 GWh sur le
bras Moson du Danube, l'autre une production de 174GWh sur l'ancien
lit du Danube). L'alimentation en eau des bras secondaires du Danube
sur la rive tchécoslovaque devait êtreassurée grâce à deux prises d'eau

situées,dans le canal de dérivation, à DobrohoSt' eta GabCikovo. Une
solution devait êtretrouvéepour la rive hongroise. En outre, la question
de l'approfondissen-lent du lit du Danube au confluent du canal de déri-
vation et de l'ancien lit du fleuve restait posée.
Le 23 juillet 1991, le Gouvernement slovaque décida de ((commencer
en septembre 1991 les constructions en vue de permettre la mise en

exploitation du projet de GabCikovo grâce à la solution provisoire)).
Cette décisionfut entérinéepar le Gouvernement fédéraltchécoslovaque
le 25juillet. Les travaux relatifs à la variCncommencèrent en novem-
bre 1991. Les discuijsions se poursuivirent en vain entre les deux parties27 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

to the Czechoslovak Government a Note Verbale terminating the 1977
Treaty with effect from 25 May 1992. On 15 October 1992, Czechoslo-
vakia began work to enable the Danube to be closed and, starting on
23 October, proceeded to the damming of the river.

24. On 23 October 1992, the Court was seised of an "Application of

the Republic of Hungary v. The Czech and Slovak Federal Republic on
the Diversion of the Danube River"; however, Hungary acknowledged
that there was no basis on which the Court could have founded its juris-
diction to entertain that application, on which Czechoslovakia took no
action. In the meanwhile, the Commission of the European Communities
had offered to mediate and, during a meeting of the two parties with the

Commission held in London on 28 October 1992,the parties entered into
a series of interim undertakings. They principally agreed that the dispute
would be submitted to the International Court of Justice, that a tripartite
fact-finding mission should report on Variant C not later than 31 Octo-
ber, and that a tripartite group of independent experts would submit sug-
gestions as to emergency measures to be taken.

25. On 1 January 1993 Slovakia became an independent State. On
7 April 1993, the "Special Agreement for Submission to the International
Court of Justice of the Differences between the Republic of Hungary and
the Slovak Republic concerning the GabEikovo-Nagymaros Project" was
signed in Brussels, the text of whichs reproduced in paragraph 2 above.
After the SpecialAgreement was notified to the Court, Hungary informed
the Court, by a letter dated 9 August 1993, that it considered its "initial

Application [to bel now without object, and . . . lapsed".
According to Article 4 of the Special Agreement, "The Parties [agreed]
that, pending the final Judgment of the Court, they [would]establish and
implement a temporary water management régime for the Danube."
However, this régime could not easily be settled. The filling of the
~unovo dam had rapidly led to a major reduction in the flow and in the

level of the downstream waters in the old bed of the Danubeas well as in
the side-arms of the river. On 26 August 1993, Hungary and Slovakia
reached agreement on the setting up of a tripartite group of experts (one
expert designated by each party and three independent experts designated
by the Commission of the European Communities)

"In order to provide reliable and undisputed data on the most
important effects of the current water discharge and the remedial
measures already undertaken as well as to make recommendations
for appropriate measures."

On 1 December 1993, the experts designated by the Commission of the
European Communities recommended the adoption of various measures
to remedy the situation on a temporary basis. The Parties were unable to

agree on these recommendations. After lengthy negotiations, they finally
concluded an Agreement "concerning CertainTemporary Technical Meas-
ures and Discharges in the Danube and Mosoni branch of the Danube",et, le 19mai 1992,le Gouvernement hongrois transmit au Gouvernement
tchécoslovaque une note verbale mettant fin, à compter du 25 mai 1992,
au traitéde 1977. Le 15octobre 1992, la Tchécoslovaquie entama les tra-

vaux devant permettre la fermeture du Danube et elle procéda, à partir
du 23 octobre, au barrage du fleuve.
24. Le 23 octobre 1992, la Cour fut saisie d'une ((requêtede la Répu-
blique de Hongrie contre la République fédérative tchèqueet slovaque
concernant le détournement du Danube)): toutefois. la Hongrie recon-
naissait qu'il n'y avait aucune base sur laquelle la ~o'ur eût pu fonder sa

compétence pour connaître de cette requête, à laquelle la Tchécoslova-
quie ne donna pas suite. Dans l'intervalle, la Commission des Commu-
nautés européennesavait offert sa médiation et, lors d'une réunion tenue
à Londres le 28 octobre 1992 entre les deux parties et la Commission, les
parties prirent divers engagements transitoires. Elles convinrent surtout

que le différend serait soumis à la Cour internationale de Justice, qu'une
mission d'enquête tripartite ferait rapport sur la variante C le 31octobre
au plus tard et qu'un groupe tripartite d'experts indépendants ferait des
propositions concernant les mesures d'urgence à prendre.
25. Le 1"'janvier 1993, la Slovaquie devint un Etat indépendant. Le
7 avril 1993 fut signéà Bruxelles le ((Compromis visant à soumettre à la

Cour internationale de Justice les contestations entre la République de
Hongrie et la République slovaque concernant le projet Gabtikovo-
Nagymaros)), dont le texte est reproduit au paragraphe 2 ci-dessus. Après
la notification du compromis à la Cour, la Hongrie, par lettre du 9 août
1993, informa la Cour qu'elle considérait sa ((requêteinitiale [comme

désormais] sans objet et ...caduque)).
Aux termes de l'article 4 du compromis: «Les Parties [étaient conve-
nues], en attendant l'arrêtdéfinitifde la Cour, d'établiret d'appliquer un
régimetemporaire dlegestion des eaux pour le Danube. ))Toutefois, l'éta-
blissement de ce régime nefut pas aisé. La mise en eau du barrage de
Cunovo avait rapidement entraîné une importante réduction du débit et

du niveau des eaux en aval dans l'ancien lit du Danube comme dans les
bras secondaires du fleuve. Le 26 août 1993, la Hongrie et la Slovaquie
s'accordèrent pour créerun groupe tripartite d'experts (un expert nommé
par chaque partie et trois experts indépendants nommés par la Commis-
sion des Communautés européennes)

«afin de recueilllirdes donnéesfiables et incontestées sur les effets les
plus importants du débit actuel et des mesures correctives déjà entre-

prises, ainsi qulr pour formuler des recommandations sur les mesures
appropriées)).
Le 1"'décembre 19'93,les experts nommés par la Commission des Com-

munautéseuropéeninesrecommandèrent l'adoption de diverses mesures en
vue de remédier, à titre temporaire, à la situation. Les Parties ne purent se
mettre d'accord sur ces recommandations. A l'issue de longues négocia-
tions, elles conclurent finalement, le 19avril 1995, un accord ((concernant
certaines mesures telchniquestemporaires et lesdébitsd'eaudans le Danube28 GABCIKOVO-NAGYM PAOJOCT (JUDGMENT)

on 19April 1995.That Agreement raised the discharge of water into the
Mosoni Danube to 43 m3/s.It provided for an annual average of 400 m3/s
in the old bed (not including flood waters). Lastly,it provided forthe con-
struction by Hungary of a partially underwater weir near to Dunakiliti
with a viewto improving the water supply to the side-arms of the Danube

on the Hungarian side. It was specified that this temporary agreement
would come to an end 14days after the Judgment of the Court.

26. The first subparagraph of the Preamble to the Special Agreement
covers the disputes arising between Czechoslovakia and Hungary con-
cerning the application and termination, not only of the 1977Treaty, but
also of "related instruments"; the subparagraph specifies that, for the
purposes of the Special Agreement, the 1977Treaty and the said instru-

ments shall be referred to as "the Treaty". "The Treaty" is expressly
referred to in the wording of the questions submitted to the Court in
Article 2, paragraph 1, subparagraphs (a) and (ci, of the Special
Agreement.
The Special Agreement however does not definethe concept of "related
instruments", nor does it list them. As for the Parties, they gave some
consideration to that question- essentially in the written proceedin-s
without reaching agreement as to the exact meaning of the expression or
as to the actual instruments referred to. The Court notes however that
the Parties seemed to agree to consider that that expression covers at

least the instruments linked to the 1977Treaty which implement it, such
as the Agreement on mutual assistance of 16 September 1977 and its
amending Protocols dated, respectively, 10October 1983and 6 February
1989 (see paragraph 21 above), and the Agreement as to the common
operational regulations of Plenipotentiariesulfillingduties related to the
construction and operation of the Gabtikovo-Nagymaros Barrage Sys-
tem signed in Bratislava on 11October 1979.The Court notes that Hun-
gary, unlike Slovakia, declined to apply the description of related instru-
ments to the 1977Treaty to theJoint Contractual Plan (see paragraph 19
above), which it refused to see as "an agreement at the same level as the
other . . related Treaties and inter-State agreements".

Lastly the Court notes that the Parties, in setting out the replies which ,
should in their view be given to the questions put in the Special Agree-
ment, concentrated their reasoning on the 1977 Treaty; and that they
would appear to have extended their arguments to "related instruments"
in considering them as accessories to a whole treaty system, whose fate
was in principle linked to that of the main part, the 1977 Treaty. The
Court takes note of the positions of the Parties and considers that its
not need to go into this matter further at this juncture. PROJET GABC~KOVO-NAGYMAROS (ARRÉT) 28

et le bras Moson du Danube)). Cet accord portait le débit d'eaudans le
bras Moson à 43 m3/s. 11prévoyait une moyenne annuelle de 400 m3/s
dans l'ancien lit (en c:enon compris leseaux de crue). Il prescrivait enfin la
construction par la Hongrie d'un déversoir partiellement noyé prèd se
Dunakiliti, en vue dqaméliorerl'alimentation en eau des bras secondaires

du Danube du côté hongrois. Il était préciséque cet accord temporaire
prendrait fin quatorix jours après le prononcéde l'arrêtde la Cour.

26. Le premier alinéadu préambule du compromis vise les contesta-
tions surgies entre la Tchécoslovaquieet la Hongrieconcernant l'applica-
tion et la terminaison non seulement du traité de 1977, mais aussi des
((instruments y afférents));l'alinéaprécisequ'aux fins du compromis le
traitéde 1977et lesdits instruments seront dénommés le «traité». JI est
expressémentfait référenceau «traité» dans le texte des questions posées
à la Cour à l'article 2, paragraphe 1, alinéaa) etc), du compromis.

Le compromis ne définittoutefois pas la notion d'<(instruments ..affé-
rents)) au traitéde 11977et n'énumèrepas davantage ceux-ci. Quant aux
Parties, elles ont consacré quelques développements à cette question-
essentiellement dans.la procédureécrite - sans parvenir à s'entendre sur
le sens exact de l'expression nisur les instruments concrets auxquels elle
renverrait. La Cour constate cependant que les Parties paraissent s'accor-
der pour considérer que cette expression vise au moins les instruments
liésau traitéde 1977qui en assurent la mise en Œuvre,tels que I'accord
d'assistance mutuelle du 16septembre 1977et sesprotocoles modificatifs
en date, respectivement, du 10octobre 1983et du 6 février 1989(voir para-
graphe 21 ci-dessus), et I'accord relatifla réglementation opérationnelle

commune applicabbt aux plénipotentiaires s'acquittant de fonctions liées
à la construction et à l'exploitation du système de barrage de GabCi-
kovo-Nagymaros, signé à Bratislavale II octobre 1979. LaCour note que la
Hongrie, contrairement à la Slovaquie,a déniélecaractère d'instrumentaffé-
rent au traité de 1977 au plan contractuel conjoint (voir paragraphe 19
ci-dessus), dans lequel elle a refuséde voir «un accord au même titre
que les autres traitéset accords entre Etats...liés[au traitéde 19771)).
La Cour fera enfin observer qu'en exposant quellessont, à leur sens, les
réponsesqui devraient être données aux questionsposéesdans le compro-
mis, les Parties ont concentréleur argumentation sur le traitéde 1977; et
qu'elles paraissenta.voirétenduleurs arguments à des instruments y affé-
rents)) en les considérant commedes élémentsaccessoires d'un ensemble

conventionnel, dont le sort étaiten principe lié celui de l'élémenptrinci-
pal constituépar le traité.La Cour prend acte de ces positions des Parties
et estime ne pas avoir à approfondir davantage cette question àce stade.29 GABCIKOVO-NAGYM ARROEST (JUDGMENT)

27. The Court will now turn to a consideration of the questions
submitted by the Parties. In terms of Article 2, paragraph 1 (a), of the
Special Agreement, the Court is requested to decide first

"whether the Republic of Hungary was entitled to suspend and sub-
sequently abandon, in 1989, the works on the Nagymaros Project
and on the part of the GabCikovo Project for which the Treaty
attributed responsibility to the Republic of Hungary".

28. The Court would recall that the Gabrikovo-Nagymaros System of
Locks is characterized in Article 1, paragraph1, of the 1977Treaty as a
"single and indivisible operational system of works".
The principal works which were to constitute this system have been

described in general terms above (see paragraph 18). Details of them are
given in paragraphs 2 and 3 of Article 1 of the Treaty.
For GabMkovo, paragraph 2 lists the following works:

"(a) the Dunakiliti-HruSov head-water installations in the Danube
sector atr.km. (river kilometre(s)) 1860-1842, designed for a
maximum flood stage of 131.10 m.B. (metres above sea-level.
Baltic system), in Hungarian and Czechoslovak territory;

(6) the Dunakiliti dam and auxiliary navigation lock at r.km.

1842, in Hungarian territory ;
(c) the by-pass canal (head-water canal and tail-water canal) at
r.km. 1842-181 1,in Czechoslovak territory ;
(rl) series of locks on the by-pass canal, in Czechoslovak territory,
consisting of a hydroelectric power plant with installed capa-
city of 720MW, double navigation locks and appurtenances

thereto;
(el improved old bed of the Danube at r.km. 1842-1811, in the
joint Hungarian-Czechoslovak section;
(f) deepened and regulated bed of the Danube at r.km. 1811-
1791, in the joint Hungarian-Czechoslovak section."

For Nagymaros, paragraph 3specifies the following works:
"(a) head-water installations and flood-control works in the

Danube sector at r.km. 1791-1696.25 and in the sectors of
tributaries affected by flood waters, designed for a maximum
flood stage of 107.83 m.B., in Hungarian and Czechoslovak
territory;

(6) series of locks at r.km. 1696.25, in Hungarian territory, con-
sisting of a dam, a hydroelectric power plant with installed
capacity of 158 MW, double navigation locks and appur-
tenances thereto;
(ci deepened and regulated bed of the Danube, in both its
branches, at r.km. 1696.25-1657, in the Hungarian section." PROJET GABCIKOVO-NAGYMAROS (ARRET) 29

27. La Cour passera maintenant à l'examen des questions soumises
par les Parties. Au:< termes de l'article 2, paragraphe 1, alinéa a), du
compromis, il est demandé en premier lieu i la Cour de dire

«si la République de Hongrie était en droit de suspendre puis
d'abandonner, en 1989, les travaux relatifs au projet de Nagymaros
ainsi qu'A la partie du projet de Gabeikovo dont la République de
Hongrie est responsable aux termes du traité».

28. La Cour rappellera que le système d'éclusesde Gabtikovo-Nagy-
maros est qualifié,a.uparagraphe 1 de l'article premier du traitéde 1977,
de ((systèmed'ouvrages opérationnel, unique et indivisible)).

Les principaux ouvrages qui devaient constituer ce système ont été
décritsen termes générauxci-dessus (voir paragraphe 18). Le détailen est
donné aux paragraphes 2 et 3 de l'article premier du traité.
S'agissant de GabEikovo, le paragraphe 2 énumèreles ouvrages suivants:

«a) les install;ations d'amont de Dunakiliti-HruSov, dans le secteur
du Danube, aux kilomètres 1860-1842,conçues pour un niveau
maximal des hautes eaux de 131,10 mètres au-dessus du niveau
de la mer. système de la Baltique, en territoires hongrois et
~chécoslovaque;

b) le barrage de Dunakiliti et l'éclusede navigation auxiliaire au
kilomètre 1842,en territoire hongrois;
c) le canal de dérivation (canal d'amont et canal d'aval) aux kilo-
mètres 1842-18 11, en territoire tchécoslovaque;
d) une série d'écluses sur le canal de dérivation, en territoire
tchécoslovaque, comprenant une centrale hydro-électrique
d'une capacité installéede 720 MW, des éclusesde navigation

doubles et le matérielconnexe:
e/ une amélioration de l'ancien lit du Danube aux kilomètres
1842-18 11, dans le secteur commun hungaro-tchécoslovaque ;
f) l'approfo.ndissementet la régulationdu lit du Danube aux kilomè-
tres1811 1791,dans le secteur conjoint hungaro-tchécoslovaque».

Quant 3 Nagymaros, le paragraphe 3 énumèreles ouvrages ci-après:

installati~snsd'amont et ouvrages de protection contre les inon-
dations dlans lesecteur du Danube aux kilomètres 179 1-1696,25
et dans les secteurs des affluents affectés par les crues, conçus
pour un niveau maximum des hautes eaux de 107,83 mètres
au-dessus du niveau de la mer, système de la Baltique, en ter-
ritoires hongrois et tcliécoslovaque;

6) une série d'écluses au kilomètre 1696,25, en territoire hon-
grois, comprenant un barrage, une centrale hydro-électrique
d'une capacité installéede 158 MW, des éclusesde navigation
doubles et un matériel connexe;
c) l'approfondissement et la régulation du lit du Danube, dans ses
deux branches, aux kilomètres 1696,251657, dans le secteur
hongrois >>.30 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

29. Moreover, the precise breakdown of the works incumbent on each
party was set out in Article 5, paragraph 5, of the 1977 Treaty, as fol-
lows:

"5. The labour and supplies required for the realization of the
joint investment shall be apportioned between the Contracting
Parties in the following manner:

(a) The Czechoslovak Party shall be responsible for:
(1) the Dunakiliti-HruSov head-water installations on the left
bank, in Czechoslovak territory ;
(2) the head-water canal of the by-pass canal, in Czecho-
slovak territory ;
(3) the GabCikovo series of locks, in Czechoslovak territory ;
(4) the flood-control works of the Nagymaros head-water
installations, in Czechoslovak territory, with the exception
of the lower Ipel district;

(5) restoration of vegetation in Czechoslovak territory;

(b) The Hungarian Party shall be responsible for

(1) the Dunakiliti-HruSov head-water installations on the
right bank, in Czechoslovak territory, including the con-
necting weir and the diversionary weir;
(2) the Dunakiliti-HruSov head-water installations on the
right bank, in Hungarian territory ;
(3) the Dunakiliti dam, in Hungarian territory;
(4) the tail-water canal of the by-pass canal, in Czechoslovak
territory;
(5) deepening of the bed of the Danube below Palkovicovo,
in Hungarian and Czechoslovak territory ;
(6) improvement of the old bed of the Danube, in Hungarian
and Czechoslovak territory ;

(7) operational equipment of the GabCikovo system of locks
(transportequipment, maintenance machinery), in Czecho-
slovak territory ;
(8) the flood-control works of the Nagymaros head-water
installations in the lower Ipel district, in Czechoslovak
territory;
(9) the flood-control works of the Nagymaros head-water
installations, in Hungarian territory;
(10) the Nagymaros series of locks, in Hungarian territory;
(11) deepening of the tail-water bed below the Nagymaros
system of locks, in Hungarian territory;
(12) operational equipment of the Nagymaros system of locks
(transport equipment, maintenance machinery), in Hun-
garian territory;

(13) restoration of vegetation in Hungarian territory." PROJET GABC~KOVO-NAGYMAROS (ARRET) 30

29. Par ailleurs. la ventilation réc ci ses travaux incombant a chaque
partie étaitopéréec 'omme suit a; paragraphe 5 de l'articl5 du traité-de
1977:

«5. La main-d'Œuvre et les fournitures nécessairespour la réalisa-
tion de l'investissement conjoint seront réparties comme suit entre
les parties contractantes:

U) la partie tchécoslovaque sera responsable:
1) des installations d'amont de Dunakiliti-HruSov sur la rive
gauche, en territoire tchécoslovaque;

2) du canal d'amont du canal de dérivation, en territoire tché-
coslovaclue;
3) de la série d'éclusese GabCikovo, en territoire tchécoslovaque;
4) des ouvrages de protection contre les inondations des instal-
lations d'amont de Nagymaros, en territoire tchécoslovaque,
à l'exception du district inférieur d'lpel;

5) de la remise en état de la végétation enterritoire tchécoslo-
vaque ;
6) la partie hongroise sera responsable:

1) des installations d'amont de Dunakiliti-HruSov, sur la rive
droite, en territoire tchécoslovaque, y compris la vanne de
connexion et la vanne de détournement;
2) des installations d'amont de Dunakiliti-HruSov, sur la rive
droite, i:n territoire hongrois;

3) du barrage de Dunakiliti, en territoire hongrois;
4) du canal d'aval du canal de dérivation, en territoire tchéco-
slovaque ;
5) de l'approfondissement du lit du Danube en aval de Palkovi-
Covo, eiî territoire hongrois et en territoire tchécoslovaque;
6) de I'am~bliorationde l'ancien lit du Danube, en territoire hon-
grois et en territoire tchécoslovaque;

7) du matlbriel opérationnel du système d'éclusesde GabCikovo
(matériel de transport, machines d'entretien), en territoire
tchécoslovaque;
8) des ouvrages de protection contre les inondations des instal-
lations d'amont de Nagymaros dans le district inférieur d'lpel,
en territoire tchécoslovaque;

9) des ouvrages de protection contre les inondations des instal-
lations d'amont de Nagymaros, en territoire hongrois;
10) de la serie d'éclusesde Nagymaros, en territoire hongrois;
11) de I'approfondissement du lit d'aval en dessous du système
d'éclusesde Nagymaros, en territoire hongrois;
12) du matériel opérationnel du système d'écluses deNagymaros
(matériel de transport, machines d'entretien), en territoire

hongrois ;
13) de la remise en état de la végétation enterritoire hongrois.))31 GABCIKOVO-NAGYM AROJEST (JUDGMENT)

30. As the Court has already indicated (see paragraph 18 above), Ar-
ticle 1, paragraph4, of the 1977 Treaty stipulated in general terms that
the "technical specifications" concerning the System of Locks would be

included in the "ioint contractual dan". The schedule of work had for its
part been fixed in an Agreement on mutual assistance signed by the two
parties on 16 September 1977 (see paragraph 21 above). In accordance
with the provisions of Article 1, paragraph 1, of that Agreement, the
whole of the works of the barr.+, svstem were to have been comoleted in
1991. As indicated in paragraph 2 of that same article, a summary con-

struction schedule was appended to the Agreement, and provision was
made for a more detailed schedule to be worked out in the Joint Con-
tractual Plan. The Agreement of 16 September 1977 was twice amended
further. By a Protocol signed on 10October 1983,the parties agreed first
to postpone the works and the putting into operation of the power plants
for four more years; then, by a Protocol signed on6 February 1989, the

parties decided, conversely, to bring them forward by 15 months, the
whole system having to be operational in 1994. A new summary con-
struction schedule was appended to each of those Protocols; those sched-
ules were in turn to be implemented by means of new detailed schedules,
included in the Joint ContractualPlan.

31. In spring 1989, the work on the GabCikovo sector was well
advanced: the Dunakiliti dam was 90 per cent complete, the Gabëikovo
dam was 85 per cent complete, and the bypass canal was between 60 per
cent complete (downstream of Gabcikovo) and 95 per cent complete
(upstream of GabCikovo) and the dykes of the Dunakiliti-HruSov reser-

voir were between 70 and 98 per cent complete, depending on the loca-
tion. This was not the case in the Nagymaros sector where, although
dykes had been built, the only structure relating to the dam itself was the
coffer-dam which was to facilitate its construction.
32. In the wake of the profound political and economic changes which
occurred at this time in central Europe, the Gabcikovo-Nagymaros

Project was the object, in Czechoslovakia and more particularly in Hun-
gary, of increasing apprehension, both within a section of public opinion
and in some scientific circles. The uncertainties not only about the eco-
nomic viability of the Project, but also, and more so, as to the guarantees
it offered for preservation of the environment, engendered a climate of
growing concern and opposition with regard to the Project.

33. It was against this background that, on 13May 1989,the Govern-
ment of Hungary adopted a resolution to suspend works at Nagymaros,
and ordered

"the Ministers concerned to commission further studies inorder to

place the Council of Ministers in a position where it can make well-
founded suggestions to the Parliament in connection with the amend-
ment of the international treaty on tinvestment. In the interests of 30. Comme la Cour l'a déjà indiqué(voir paragraphe 18), le para-
graphe 4 de l'article premier du traité de 1977 stipulait en termes géné-
raux que les ((spécificationstechniques)) concernant le système d'écluses
seraient fixéesdans le «plan contractuel conjoint)). Le calendrier de réa-

lisation des travaux avait pour sa part étéfixédans I'accord d'assistance
mutuelle signé par les deux parties le 16 septembre 1977 (voir para-
graphe 21 ci-dessus). Conformément aux dispositions di1paragraphe 1 de
l'article premier de cet accord, l'ensemble des travaux du systèmede bar-
rage devaient être achevés en 1991. Ainsi qu'il était indiquéau para-
graphe 2 du même article,un calendrier sommaire des travaux de construc-

tion était annexéà l'accord; ily étaitprévuqu'un échéancier plus détaillé
serait établi dans le cadre du plan contractuel conjoint. L'accord du
16 septembre 1977 fut amendé à deux reprises. Par un protocole signéle
10 octobre 1983, il fut d'abord convenu par les parties de repousser de
quatre annéesles travaux et la mise en service des centrales; puis, par un
protocole signéle 6 février 1989, les parties décidèrent à l'inverse de les
accélérerde quinze inois, l'ensemble du systèmedevant êtreopérationnel

en 1994. Un nouveau calendrier sommaire des travaux de construction
était annexé à chauun de ces protocoles; ces calendriers devaient à leur
tour recevoir effet ;lu moyen de nouveaux échéanciersdétaillésinscrits
dans le plan contractuel conjoint.
31. Au printemps 1989, les travaux concernant le secteur de Gab-
Eikovo étaient bien avancés: le barrage de Dunakiliti était réalisi 90 'XI,

celui de Gabi-ikovo à 85 '%,le canal de dérivation entre 60 %I(en aval de
GabEikovo) et 95 '31(en amont de GabEikovo) et les digues du réservoir
de Dunakiliti-HruSov entre 70 et 98 'XI,selon les endroits. II n'en allait
pas de mêmedans le secteur de Nagymaros où, si des digues avaient été
édifiées,le seul ouvrage relatif au barrage lui-mêmeà avoir étémis en
place était le batardeau qui devait en permettre la construction.

32. Dans le sillage des changements politiques et économiques pro-
fonds survenus à cette époque en Europe centrale, le projet GabCikovo-
Nagymaros suscita en Tchécoslovaquie et tout particulièrement en Hon-
grie de plus en plus d'appréhensions dans une partie de l'opinion
publique et du monde scientifique. Les incertitudes éprouvées, non seu-

lement quant à la viabilité économique du projet, mais aussi et plus
encore quant aux garanties qu'il présentait pour ce qui est du respect de
l'environnement, engendrèrent un climat d'inquiétude et de contestation
croissantes autour de ce projet.
33. C'est dans ce contexte que le Gouvernement hongrois adopta, le
13mai 1989,une rksolution par laquelle il suspendait les travaux à Nagy-

maros et ordonnait

«aux ministres intéressésde faire faire de nouvelles études afin de
mettre le conseil des ministres en mesure de présenter au Parlement
des suggestions dùment fondéesconcernant la modification du traité
international sur l'investissement considéré.Il nous faut, à cet égard,32 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

the above, we must examine the international and legal conse-
quences, the technical considerations, the obligations related to con-
tinuous navigation on the Danube and the environmental/ecological
and seismic impacts of the eventual stopping of the Nagymaros
investment. To be further examined are the opportunities for the
replacement of the lost electric energy and the procedures for mini-
mising claims for compensation."

The suspension of the works at Nagymaros was intended to last for the
duration of these studies, which were to be completed by 31 July 1989.
Czechoslovakia immediately protested and a document defining the posi-
tion of Czechoslovakia was transmitted to the Ambassador of Hungary
in Prague on 15May 1989.The Prime Ministers of the two countries met
on 24 May 1989,but their talks did not lead to any tangible result. On
2 June, the Hungarian Parliament authorized the Government to begin
negotiations with Czechoslovakia for the purpose of modifying the 1977
Treaty.
34. At a meeting held by the Plenipotentiaries on 8 and 9 June 1989,
Hungary gave Czechoslovakia a number of assurances concerning the
continuation of works in the GabCikovo sector, and the signed Protocol
which records that meeting contains the following passage:

"The Hungarian Government Commissioner and the Hungarian
Plenipotentiary stated, that the Hungarian side will complete con-
struction of theGabCikovo Project in the agreed time and in accord-
ance with the project plans. Directives have already been given to
continue works suspended in the area due to misunderstanding."

These assurances were reiterated in a letter that the Commissioner of the
Government of Hungary addressed to the Czechoslovak Plenipotentiary
on 9 June 1989.
3.5. With regard to the suspension of work at Nagymaros, the Hungar-
ian Deputy Prime Minister, in a letter dated 24June 1989addressed to his
Czechoslovak counterpart, expressed himselfin the following terms:

"The Hungarian Academy of Sciences(HAS)has studied the envi-
ronmental, ecological and water quality as well as the seismological
impacts of abandoning or implementing the Nagymaros Barrage of
theGabCikovo-Nagymaros Barrage System (GNBS).

.............................
Having studied the expected impacts of the construction in accord-
ance with the original plan, the Committee [ad hoc] of the Academy
[set up for this purpose] came to the conclusion that we do not have
adequate knowledge of the consequences of environmental risks.

In its opinion, the risk of constructing the Barrage System in
accordance with the original plan cannot be considered acceptable.
Of course, it cannot be stated either that the adverse impacts will PROJET GABC~KOVO-NAGYMAROS (ARRÉT) 32

examiner les conséquences internationales et juridiques, les aspects
techniques, l'obligation que nous avons d'assurer la navigation conti-

nue sur le Danube et les incidences du point de vue écologique et
sismique de l'arrêtéventuel de l'investissement de Nagymaros. 11
convient en outre d'examiner les possibilitésde remplacer l'énergie
électrique perdue ainsi que les moyens à mettre en Œuvre pour
réduireau minimum les demandes d'indemnisation. »
La suspension des travaux à Nagymaros était prévuepour le temps de la
réalisationde cesétudes;celles-cidevaient êtreterminéespour le 31juillet
1989.La Tchécoslovaquieprotesta immédiatement; un document définis-

sant la position tchécoslovaque fut remisàl'ambassadeur de Hongrie à
Prague le 15mai 1989. Lespremiers ministres des deux pays se rencon-
trèrent le 23 mai 1989,sans que leurs entretiens n'aboutissentes résul-
tats tangibles. Lejuin, le Parlement hongrois autorisa le gouvernement
à entamer des négociationsavec la Tchécoslovaquie iil'effet de modifier
le traitéde 1977.
34. Au cours d'une réunion que les plénipotentiairestinrent les 8 et
9 juin 1989,la Hongrie donna à la Tchécoslovaquiediverses assurances
concernant la poursuite des travaux dans le secteur debCikovo; le pro-
tocole signéqui rend compte de cette réunion contientle passage suivant:

«Le commissaire du Gouvernement hongrois et le plénipotentiaire
hongrois ont fait savoir que la partie hongroise mèneraià bien la
réalisation du projet de GabCikovo dans les délais convenus et
conformément aux plans du projet. Des directives ont déjàétédon-
nées pour que les travaux suspendus pour cause de malentendu
reprennent dans la zone.

Ces assurances furent réitéréesdans une lettre que le commissaire du
Gouvernement hongrois adressa au plénipotentiaire tchécoslovaquele
9juin 1989.
35. S'agissant de la suspension des travauxà Nagymaros, le vice-pre-
mier ministre hongrois, dans une lettre en date du 24juin 1989adresséà
son homologue tchécoslovaque,s'exprima dans les termes suivants:

((L'Académiedes sciences de Hongrie (ASH) a étudiéles consé-
quences qu'aurait sur l'environnement, l'écologieet la qualité de
l'eau ainsi que sur la situation sismologique, la décisiond'abandon-
ner ou de réaliserla construction du barrage de Nagymaros, dans le
cadre du systèmede barrage de GabCikovo-Nagymaros.
.............................
Aprèsavoir étudiéles conséquencesprévuesde la construction réa-

lisée selonle plan initial, lecomitéhoc]de l'Académie[créé à cette
fin] est arriàéla conclusion que nous ne disposons pas de connais-
sances satisfaisantes sur les conséquencesdes risques écologiques.
A son avis, le risque qu'entraînerait la construction du système de
barrage conformémentau plan initial ne peutêtreconsidéré comme
acceptable.On ne peut évidemment pasdéclarernon plusque desconsé-33 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

ensue for certain, therefore, according to their recommendation,
further thorough and time consuming studies are necessary."

36. The Hungarian and Czechoslovak Prime Ministers met again on
20 July 1989 to no avail. lmmediately after that meeting, the Hungarian
Government adopted a second resolution, under which the suspension of
work at Nagymaros was extended to 31 October 1989. However, this
resolution went further, as it also prescribed the suspension, until the

same date, of the "Preparatory works on the closure of the riverbed at
. . . Dunakiliti"; the purpose of this measurewas to invite "international
scientific institutions [and] foreign scientific institutes and experts" to co-
operate with "the Hungarian and Czechoslovak institutes and experts"
with a view to an assessment of the ecological impact of the Project and
the "development of a technical and operational water quality guarantee
system and . . . its implementation".

37. In the ensuing period, negotiations were conducted at various levels
between the two States, but proved fruitless. Finally, by a letter dated
4 October 1989, the Hungarian Prime Minister formally proposed to
Czechoslovakia that the Nagymaros sector of the Project be abandoned
and that an agreement be concluded with a view to reducing the ecologi-
cal risks associated with the Gabëikovo sector of the Project. He pro-

posed that that agreement should be concluded before 30 July 1990.
The two Heads of Government met on 26 October 1989, and were
unable to reach agreement. By a Note Verbale dated 30 October 1989,
Czechoslovakia, confirming the views it had expressed during those talks,
proposed to Hungary that they should negotiate an agreement on a sys-
tem of technical, operational and ecological guarantees relating to the

Gabëikovo-Nagymaros Project, "on the assumption that the Hungarian
party will immediatelycommence preparatory work on the refilling of the
Danube's bed in the region of Dunakiliti". It added that the technical
principles of the agreement could be initialled within two weeks and that
the agreement itself ought to be signed before the end of March 1990.
After the principles had been initialled, Hungary "[was to] start the actual

closure of the Danube bed". Czechoslovakia further stated its willingness
to "conclu[de] . . . a separate agreement in which both parties would
oblige themselves to limitations or exclusion of peak hour operation
mode of the . . . System". It also proposed "to return to deadlines indi-
cated in the Protocol of October 1983", the Nagymaros construction
deadlines being thus extended by 15months, so as to enable Hungary to

take advantage of the time thus gained to study the ecological issues and
formulate its own proposais in due time. Czechoslovakia concluded by
announcing that, should Hungary continue unilaterally to breach the
Treaty, Czechoslovakia would proceed with a provisional solution.

In the meantime, the Hungarian Government had on 27 October
adopted a further resolution, deciding to abandon the construction of the PROJET GABCIKOVO-NAGYM (ARROET) 33

quences préjudiciables se produiraient inévitablement et il est donc
nécessaire.conformémentà la recommandation du comité, d'effectuer
de nouvelles études approfondiesqui exigeront beaucoup de temps.))

36. Les premiers ministres hongrois et tchécoslovaque se rencontrèrent

de nouveau le 20juillet 1989,sans succès.Aussitôt après cette rencontre,
le Gouvernement hongrois adopta une deuxièmerésolution, aux termes de
laquelle la suspension des travaux A Nagymaros était prorogée jusqu'au
31 octobre 1989.Cette résolution allait cependant plus loin, car elle pres-
crivait également la suspension, jusqu'à la mêmedate, des ctravaux pré-

paratoires en vue de la fermeture du lit du fleuve à Dunakilitin; cette
mesure avait pour objet d'inviter «[des] institutions scientifiques interna-
tionales et ... [des] instituts et experts scientifiques étrangers)) à coopérer
avec «[les]institutsetexpertshongrois et tchécoslovaques»en vue d'appré-
cier les incidences écologiquesdu projet et de ((mettre au point et réaliser
un systèmetechnique et opérationnel garantissant la qualité de l'eau)).

37. Dans la période qui suivit, des négociations furent menéesà divers
niveaux entre les deux Etats, mais elles s'avérèrent infructueuses.Finale-
ment, par lettre en date du 4 octobre 1989, le premier ministre hongrois
proposa formellement à la Tchécoslovaquie l'abandon du projet dans le
secteur de Nagymaros et la conclusion d'un accord ayant pour objet de

réduire les risques écologiques liésau projet dans le secteur de Gab-
Cikovo. 11suggéraitque cet accord soit conclu avant le 30 juillet 1990.
Les deux chefs de gouvernement se rencontrèrent le 26 octobre 1989et
ne purent parvenir iiun accord. Par note verbale du 30 octobre 1989, la
Tchécoslovaquie, confirmant le point de vue qu'elle avait exprimé lors de

ces entretiens, proposa à la Hongrie de négocierun accord au sujet d'un
systèmede garanties techniques, opérationnelles et écologiques relatif au
projet GabEikovo-Nagymaros, «en partant de l'hypothèse que la partie
hongroise commencera immédiatement les travaux de préparation du
remplissage du lit du Danube dans la régionde Dunakiliti)). Elle ajoutait

que les principes techniques dudit accord pourraient être paraphés sous
quinzaine et que l'accord lui-mêmedevrait êtresignéavant la fin mars
1990. Dès le paraphe, la Hongrie ~devra[it] commencer à fermer effecti-
vement le lit du Danube)). La Tchécoslovaquie se disait en outre prêteà
((conclure un accord distinct par lequel les deux parties s'engageraient

d'elles-mêmesà limiter ou à exclure le fonctionnement en régime de
pointe du système». Elle proposait encore (<derevenir ..aux dates limites
indiquéesdans le protocole d'octobre 1983», les délaisde construction de
Nagymaros étant ainsi prorogés de quinze mois afin de permettre à la
Hongrie de mettre a profit le temps gagnépour étudier les questions éco-
logiques et formuler ses propositions en temps voulu. Enfin, la Tchéco-

slovaquie annonçait que, si la Hongrie continuait à enfreindre unilatéra-
lement les dispositions du traité, la Tchécoslovaquie se verrait contrainte
de mettre en Œuvre une solution provisoire.
Dans l'intervalle, le Gouvernement hongrois avait adopté le 27 octobre
1989une nouvelle résolutionpar laquelleil décidaitd'abandonner la construc-Nagymaros dam and to leave in place the measures previously adopted
for suspending the works at Dunakiliti. Then, by Notes Verbales dated
3 and 30 November 1989,Hungary proposed to Czechoslovakia a draft
treaty incorporating itsearlier proposals, relinquishing peak power opera-
tion of the Gabëikovo power plant and abandoning the construction of

the Nagymaros dam. The draft provided for the conclusion of an agree-
ment on the completion of Gabëikovo in exchange for guarantees on
protection of the environment. It finally envisaged the possibility of one
or other party seising an arbitral tribunal or the International Court of
Justice in the event that differences of view arose and persisted between
the two Governments about the construction and operation of the Gab-
Cikovodam, as well as measures to be taken to protect the environment.
Hungary stated that it was ready to proceed immediately "with the pre-
paratory operations for the Dunakiliti bed-decanting", but specifiedthat
the river would not be dammed at Dunakiliti until the agreement on
guarantees had been concluded.
38. During winter 1989-1990,the political situation in Czechoslovakia
and Hungary alike was transformed, and the new Governments were
confronted with many new problems.
In spring 1990. the new Hungarian Government, in presenting its
National Renewal Programme, announced that the whole of the Gab-

ëikovo-Nagymaros Project was a "mistake" and that it would initiate
negotiations as soon as possible with the Czechoslovak Government "on
remedying and sharing the damages". On 20 December 1990,the Hun-
garian Government adopted a resolution for the opening of negotiations
with Czechoslovakia on the termination of the Treatv b, , mutual consent
and the conclusion of an agreement addressing the consequences of the
termination. On 15February 1991,the Hungarian Plenipotentiary trans-
mitted a draft agreement along those lines to his Czechoslovak counter-
part.
On the same day, the Czechoslovak President declared that the Gab-
Cikovo-Nagymaros Project constituted a "totalitarian, gigomaniac monu-
ment which is against nature", while emphasizing that "the problem [was]
that [theGabëikovo power plant] [had]already been built". For his part,
the Czechoslovak Minister of the Environment stated, in a speech given
to Hungarian parliamentary committees on 11September 1991,that "the
G/N Project [was]an old, obsolete one", but that, if there were "many

reasons to change, modify the treaty . . it [was]not acceptable to cancel
the treaty .. .and negotiate later on".
During the ensuing period, Hungary refrained from completing the
work for which it was still responsible at Dunakiliti. Yet it continued to
maintain the structures it had already built and,at the end of 1991,com-
pleted the works relating to the tailrace canal of the bypass canal assigned
to it under Article 5, paragraph 5 (b), of the 1977Treaty.tion du barrage de Nagymaros et de maintenir les mesures de suspension
des travaux antérieurement adoptéespour Dunakiliti. Puis, par des notes
verbales en date des 3 et 30 novembre 1989, laHongrie proposa à la Tché-
coslovaquie un projet de traité concrétisantses propositions antérieures
et portant renonciation à l'exploitation de la centrale de GabCikovo en

régimede pointe et abandon de la construction du barrage de Nagymaros.
Le projet prévoyaiten outre la conclusion d'un accordsur l'achèvementde
GabEikovo au prix de garanties concernant la protection de I'environne-
ment. 11envisageait enfinla possibilitépour l'uneou l'autre partiede saisir
un tribunal arbitral ou la Cour internationale deJustice au cas où desdiver-
gences de vues auraient surgi et persistéentre les deux gouvernements au
sujet de la construction et du fonctionnement du barrage de Gabëikovo
ainsi que des mesuresà prendre pour protéger I'environnement.La Hongrie
se déclarait prête engager immédiatement«les opérations depréparation
du décantagedu lit du Danube)), mais précisaitque le fleuvene serait barré
à Dunakiliti qu'après conclusionde l'accord sur les garanties.
38. Au cours de l'hiver 1989-1990,la situation politique changea pro-
fondémenttant en Tchécoslovaquie qu'enHongrie et les nouveaux gou-
vernements eurent à faire faceà de nombreux nouveaux problèmes.
Au printemps 1990,le nouveau Gouvernement hongrois, en présentant

son((programme de renouveau national)), déclaraque l'ensembledu pro-
jet GabEikovo-Nagymaros constituait une «erreur» et qu'il engagerait
aussitôt que possible des négociations avecle Gouvernement tchécoslo-
vaque «sur la remise en l'étatdes lieux et le partage des dommages)>.Le
20 décembre 1990,le Gouvernement hongrois adopta une résolution en
vue de l'ouverture de négociations avec la Tchécoslovaquiesur la termi-
naison du traitépar consentement mutuel et la conclusion d'un accord
qui régleraitles conséquencesde cette terminaison. Le 15février1991,le
plénipotentiaire hongrois faisait parvenir à son homologue tchécoslo-
vaque un projet d'accord en ce sens.
Le mêmejour, le président tchécoslovaque déclaraque le projet GabN-
kovo-Nagymaros constituaitun «monument totalitaire,atteint de gigantisme
et contraireà la nature)),tout en soulignant que «le problème[était]que [la
centrale de GabEikovo] a[vait]déjà étéconstruite)).Pour sa part, le ministre
tchécoslovaquede I'environnement indiqua, dans un discours prononcé
devantdes commissionsdu Parlementhongroisle 11septembre 1991,que «le

projet GIN constituait un vieux projet, de caractère désuet)),mais que
s'ilexistait«de nombreuses raisons de changer, de modifier le traité ...il
n'[était]pas acceptable d'annuler le traité..et de négocierplus tard)).
La Hongrie, au cours de la périodequi suivit, s'abstint de terminer les
travaux qui lui incombaient encore à Dunakiliti. Elle continua cependant
d'entretenir les ouvrages qu'elle y avait déjà construits et, à la fin de
l'année1991,elletermina les travaux afférents au canal de fuite du canal
de dérivation,dont elle avait la responsabilitéen vertu de l'article 5, para-
graphe 5, alinéa b), du traitéde 1977.35 GABCIKOVO-NAGYMAROSPROJECT (JUDGMENT)

39. The two Parties to this case concur in recognizing that the 1977
Treaty, the above-mentioned Agreement on mutual assistance of 1977
and the Protocol of 1989were validly concluded and were duly in force
when the facts recounted above took place.

Further, they do not dispute the fact that, however flexible they may
have been, these texts did not envisage the possibility of the signatories
unilaterally suspending or abandoning the work provided for therein, or
even carryingit out according to a new schedule not approved by the two
partners.
40. Throughout the proceedings, Hungary contended that, although it
did suspend or abandon certain works, on the contrary, it never sus-
pended the application of the 1977Treaty itself. To justify its conduct, it
reliedessentially on a "state of ecological necessity".

Hungary contended that the various installations in the GabEikovo-
Nagymaros System of Locks had been designed to enable the Gabtikovo

power plant to operate in peak mode. Water would only have come
through the plant twiceeach day, at times of peak power demand. Opera-
tion in peak mode required the vast expanse (60 km') of the planned
reservoir at Dunakiliti, as well as the Nagymaros dam, which was to
alleviate the tidal effectsand reduce the variation in the water levelwn-
Streamof Gabtikovo. Such a system, considered to be more economically
profitable than using run-of-the-river plants, carried ecological risks
which it found unacceptable.

According to Hungary, the principal ecological dangers which would
have been caused by this system were as follows. At GabMkovoi
Dunakiliti, under the original Project, as specified in the Joint Contrac-

tua1 Plan, the residual discharge into the old bed of the Danube was
limited to 50m3/s,in addition to the water provided to the system of side-
arms. That volume could be increased to 200 m3/s during the growing
season. Additional discharges, and in particular a number of artificial
floods, could also be effected, at an unspecified rate. In these circum-
stances, the groundwater levelwould have fallen in most of the Szigetkoz.
Furthermore, the groundwater would then no longer have been supplied
by the Danube - which, on the contrary, would have acted as a drain -
but by the reservoir of stagnant water at Dunakiliti and the side-arms
which would have become silted up. In the long term, the quality of water
would have been seriously impaired. As for the surface water, risks of
eutrophication would have arisen, particularly in the reservoir; instead of
the old Danube there would have been a river choked with sand, where

only a relative trickle of water would have flowed.The network of arms
would have been for the most part cut off from the principal bed. The
fluvial fauna and flora, likethose in the alluvial plains, would have been
condemned to extinction.
As for Nagymaros, Hungary argued that, if that dam had been built, PROJET GABC~KOVO-NAGYMAROS (ARRET) 35

39. Les deux Parties à la présente instance s'accordent pour recon-
naître que le traité de 1977 ainsi que l'accord d'assistance mutuelle de
1977 et le protocole de 1989 susmentionnés ont été valablement conclus

et étaient dûment en vigueur au moment où se sont produits les faits ci-
dessus rapportés.
Elles ne contestent pas davantage que ces textes, aussi souples qu'ils
aient été, n'envisageaient pasla possibilité pour les signataires de sus-
pendre ou d'abandonner unilatéralement les travaux qui y étaient pré-

vus, voire de réaliser ceux-ci selon un calendrier nouveau qui n'eût pas été
agréépar les deux partenaires.
40. Tout au long de la procédure, la Hongrie a soutenu que, si elle avait
suspendu ou abandonné certains travaux, elle n'avait en revanche ja-
mais suspendu l'application du traité de 1977 lui-même. Ellea essentiel-
lement invoqué, pour justifier sa conduite, un «état de nécessitéécolo-

gique)).
La Hongrie a fait valoir que les diverses installations du système
d'éclusesde Gabzikovo-Nagymaros avaient étéconçues pour permettre à
la centrale de Gabtikovo de fonctionner en régimede pointe. L'eau ne se
serait écouléeà travers la centrale que deux fois par jour, lors des pé-

riodes de forte demande d'électricité.L'exploitation en régime de pointe
rendait nécessairesl'énorme étendue(60 km2) du réservoirprévuà Duna-
kiliti ainsi que le barrage de Nagymaros, qui devait atténuer les vagues de
fond et réduirela variation du niveau des eaux en aval de Gabëikovo. Un
tel régime, considéré comme économiquement plus rentable que I'utilisa-
tion des installations au fil de l'eau, comportait des risques écologiques

inacceptables pour elle.
D'après la Hongrie, lesprincipaux dangers écologiquesqu'aurait engen-
drésle système étaient les suivants. Pour ce qui est de GabCikovoIDuna-
kiliti, selon le projet initial, tel qu'il a été prédans le plan contrac-
tuel conjoint, le débit réservédans I'ancien lit du Danube était limitéà

50 m'is, en sus de l'eau fournie au systèmede bras. Ce volume pouvait être
porté à 200 m3/sen saison végétative. Des déversementssupplémentaires,
et notamment des inondations artificielles, pouvaient égalementêtre réa-
lisés,à un rythme non précisé.Dans ces conditions, le niveau des eaux
souterraines aurait baissé dans la plus grande partie du Szigetkoz. En
outre, la nappe aquifère aurait désormais été alimentée non plus par le

Danube - qui au contraire aurait joué le rôle de drain -, mais par le
réservoir d'eaux stagnantes de Dunakiliti et les bras secondaires qui se
seraient envasés. Sur le long terme, la qualité des eaux en aurait grave-
ment souffert. En ce qui concerne les eaux de surface, des risques d'eutro-
phisation seraient apparus, notamment dans le réservoir. A l'ancien

Danube aurait par ailleurs étésubstituée une rivière ensabléeoù n'aurait
couléqu'un filet d'eau assez mince. Le réseau des bras aurait étéisoléle
plus souvent du lit principal. La faune et la flore du fleuve, comme celles
des plaines alluviales, auraient étécondamnées à disparaître.

Quant à Nagymaros, la Hongrie a fait valoir que, si ce barrage avaitthe bed of the Danube upstream would have silted up and, consequently,
the quality of the water collected in the bank-filtered wells would have
deteriorated in this sector. What is more, the operation of the Gabëikovo
power plant in peak mode would have occasioned significant daily varia-
tions in the water level in the reservoir upstream, which would have con-
stituted a threat to aquatic habitats in particular. Furthermore, the con-
struction and operation of the Nagymaros dam would have caused the
erosion of the riverbed downstream, along Szentendre Island. The water
level of the river would therefore have fallen in this section and the yield

of the bank-filtered wells providing two-thirds of the water supply of the
city of Budapest would have appreciably diminished. The filter layer
would also have shrunk or perhaps even disappeared, and fine sediments
would have been deposited in certain pockets in the river. For this two-
fold reason, the quality of the infiltrating water would have been severely
jeopardized.
From al1these predictions, in support of which it quoted a variety of
scientific studies, Hungary concluded that a "state of ecological neces-
sitv" did indeed exist in 1989.
41. In its written pleadings, Hungary also accused Czechoslovakia of
having violated various provisions of the 1977Treaty from before 1989
- in particular Articles 15 and 19relating, respectively, to water quality
and nature protection - in refusing to take account of the now evident
ecological dangers and insisting that the works be continued, notably at
Nagymaros. In this context Hungary contended that, in accordance with

the terms of Article 3,paragraph 2, of the Agreement of 6 May 1976con-
cerning the Joint Contractual Plan, Czechoslovakia bore responsibility
for research into the Project's impact on the environment; Hungary
stressed that the research carried out by Czechoslovakia had not been
conducted adequately, the potential effects of the Project on the environ-
ment of the construction having been assessed by Czechoslovakia only
from September 1990.However, in the final stage of its argument, Hun-
gary does not appear to have sought to formulate this complaint as an
independent ground formally justifying the suspension and abandonment
of the works for which it was responsible under the 1977Treaty. Rather,
it presented the violations of the Treaty prior to 1989,which it imputes to
Czechoslovakia, as one of the elements contributing to the emergence of
a state of necessity.

42. Hungary moreover contended from the outset that its conduct in

the present case should not be evaluated only in relation to the law of
treaties. It also observed that, in accordance with the provisions of
Article 4, the Vienna Convention of 23 May 1969on the Law of Treaties
could not be applied to the 1977Treaty, which was concluded before that
Convention entered into force as between the parties. Hungary has
indeed acknowledged, with reference to the jurisprudence of the Court,
that in many respects the Convention reflectsthe existing customary law.
Hungary nonetheless stressed the need to adopt a cautious attitude, while PROJET GABCIKOVO-YAGYMAROS (ARRÊT) 36

étéconstruit, le lit du Danube en amont se serait envasé et,par suite, la
qualité deI'eau recueilliedans les puits filtrants sur berge se serait dété-
rioréedans ce secteur. Bien plus, l'exploitation de la centrale de Gab-
cikovo en régime de pointe aurait engendré d'importantes variations

journalières du niveau des eaux daris le réservoird'amont, ce qui aurait
notamment menacéles habitats aquatiques. En outre, la construction et
l'exploitation du barrage de Nagymaros auraient entraîné une érosiondu
lit en aval, le long del'île de Szentendre. De ce fait, le niveau des eaux
dans le fleuve aurait baissésur ce tronçon et la productivité des puitsil-
trants sur berge assurant, pour les deux tiers, l'alimentation en eau de la
ville de Budapest aurait sensiblement diminué.Par ailleurs, la couche fil-
trante se serait amincie et aurait même pudisparaître; des sédimentsfins
se seraient déposésdans certaines poches du fleuve.Pour cette double rai-
son, la qualité deI'eau d'infiltration aurait étégravement menacée.

De l'ensemble de ces prévisions,à l'appui desquelles elle a cité diverses
étudesscientifiques, la Hongrie a conclu qu'un «état de nécessité écolo-

gique » existait bien en 1989.
41. Dans ses écritures, laHongrie a aussi reproché à la Tchécoslova-
quie d'avoir, dès avant 1989, violédifférentesdispositions du traité de
1977 - en particulier ses articles 15 et 19 relatifs, respectivemenà,la
protection de la qualitédes eaux et$ la protection de la nature -en refu-
sant de prendre en considération les dangers écologiques qui s'étaient
alors précisés eten insistant sur la poursuite des travaux, notamment à
Nagymaros. La Hongrie a soutenu dans ce contexte que, conformément
aux termes du paragraphe 2 de l'artic3ede l'accord du 6 mai 1976relatif
au plan contractuel conjoint, lesrecherches concernant l'impact du projet
sur l'environnement incombaient à la Tchécoslovaquie; et la Hongrie a
souligné que les recherches entreprises par la partie tchécoslovaque

n'avaient pas été menéed se manière adéquate, les effets potentiels du
projet sur l'environnement n'ayant été évaluépsar la Tchécoslovaquie
qu'à partir de septembre 1990. Toutefois, dans le dernier état de son
argumentation, la Hongrie ne semble pas avoir entendu formuler ce grief
comme un moyen autonome tendant à justifier formellement la suspen-
sion et l'abandon des travaux dont elle était responsable aux termes du
traitéde 1977. Ellea plutôt présentéles violations du traité antérieures
1989,qu'elle impute à la Tchécoslovaquie,comme l'un des élémentsqui
ont concouru à la survenance d'un étatde nécessité.
42. La Hongrie a d'ailleurs d'embléesoutenu que sa conduite en
l'espècene devrait pas êtreappréciéeexclusivement à l'aune du droit des
traités.Elle a en outre fait observer que, conformément aux dispositions
de son article 4, la convention de Vienne du 23 mai 1969sur le droit des

traitésne pouvait s'appliquer au traitéde 1977,conclu avant que celle-ci
n'entre en vigueur entre les parties. La Hongrie a certes reconnu, en fai-
sant référence à la jurisprudence de la Cour, qu'à bien des égards la
convention traduit le droit coutumier existant. Elle n'en a pas moins sou-
ligné la nécessitéde faire preuve de prudence, tout en suggérant que la37 GABCIKOVO-NACYMAROS PROJECT (JUDGMENT)

suggesting that the Court should consider, in each case, the conformity of
the prescriptions of the Convention with customary international law.
43. Slovakia, for its part, denied that the basis for suspending or aban-
doning the performance of a treaty obligation can be found outside the

law of treaties. It acknowledged that the 1969 Vienna Convention could
not be applied as such to the 1977 Treaty, but at the same time stressed
that a number of its provisions are a reflection of pre-existing rules of
customary international law and specified that this is, in particular, the
case with the provisions of Part V relating to invalidity, termination and
suspension of the operation of treaties. Slovakia has moreover observed

that, after the Vienna Convention had entered into force for both parties,
Hungary affirmed its accession to the substantive obligations laid down
by the 1977 Treaty when it signed the Protocol of 6 February 1989 that
cut short the schedule of work: and this led it to conclude that the Vienna
Convention was applicable to'the "contractual legal régime"constituted
by the network of interrelated agreements of which the Protocol of 1989

was a part.
44. In the course of the proceedings, Slovakia argued at length that the
state of necessity upon which Hungary relied did not constitute a reason
for the suspension of a treaty obligation recognized by the law of treaties.
At the same time, it cast doubt upon whether "ecological necessity" or
"ecological risk" could, in relation to the law of State responsibility, con-

stitute a circumstance precluding the wrongfulness of an act.
In any event, Slovakia denied that there had been any kind of "eco-
logical state of necessity" in this case either in 1989 or subsequently. It
invoked the authority of various scientific studies when it claimed that
Hungary had given an exaggeratedly pessimistic description of the situa-
tion. Slovakia did not, of course, deny that ecological problems could

have arisen. However, it asserted that they could to a large extent have
been remedied. It accordingly stressed that no agreement had been
reached with respect to the modalities of operation of the GabCikovo
power plant in peak mode, and claimed that the apprehensions of Hun-
gary related only to operating conditions of an extreme kind. In the same
way, it contended that the original Project had undergone various modi-

fications since 1977 and that it would have been possible to modify it
even further, for example with respect to the discharge of water reserved
for the old bed of the Danube, or the supply of water to the side-arms by
means of underwater weirs.
45. Slovakia moreover denied that it in any way breached the 1977
Treaty - particularly its Articles15and 19 - and maintained, inter dia,

that according to the terms of Article 3,paragraph 2,of the Agreement
of 6 May 1976 relating to the Joint Contractual Plan, research into the
impact of the Project on the environment was not the exclusive respon-
sibility of Czechoslovakia but of either one of the parties, depending on
the location of the works.
Lastly, in its turn, it reproached Hungary with having adopted its uni-

lateral measures of suspension and abandonment of the works in viola- PROJET GABCIKOVO-NAGYMA (ARORSÊT) 37

Cour examine dans chaque cas si les prescriptions de la convention cor-
respondent à l'étatdu droit international coutumier.
43. La Slovaquie, pour sa part, a déniéque la suspension ou l'abandon

de l'exécutiond'une obligation conventionnelle puisse trouver son fonde-
ment hors du droit des traités. Elle a reconnu que la convention de
Vienne de 1969ne pouvait pas s'appliquer comme telle au traitéde 1977;
mais elle a en mêmetemps soulignéque nombre de ses dispositions tra-
duisent des règles préexistantes du droit international coutumier et a
préciséque tel est en particulier le cas des dispositions de sa partie V affé-

rente a la nullité,à l'extinction et à la suspension de l'application des trai-
tés.La Slovaquie a par ailleurs fait observer qu'après l'entrée en vigueur
de la convention de Vienne entre les deux parties, la Hongrie avait
confirméson adhésion aux obligations de fond crééespar le traitéde 1977
en signant le protocole du 6 février 1989 qui abrégeait le calendrier des

travaux; et elle en a conclu que la convention de Vienne s'appliquait au
((régimejuridique contractuel))constitué par le réseau d'accords liés les
uns aux autres dont le protocole de 1989 faisait partie.
44. Au cours de la procédure, la Slovaquie a longuement plaidé que
l'étatde nécessitéinvoqué par la Hongrie ne constituait pas un motif de
suspension d'une obligation conventionnelle reconnu par le droit des trai-

tés. Ellea en même tempsmis en doute que la ((nécessité écologique» ou
le «risque écologique))puissent constituer, au regard du droit de la res-
ponsabilité des Etats, une circonstance excluant I'illicéitéd'un acte.
La Slovaquie a en tout état de cause niéqu'il y ait eu en l'espèceun
quelconque «état de nécessitéécologique)), en 1989 ou par la suite. Se

réclamant de diverses étudesscientifiques, elle a prétendu que la Hongrie
avait donné une description exagérément pessimiste de la situation. La
Slovaquie n'a certes pas contestéque des problèmes écologiques auraient
pu se poser; mais elle a fait valoir qu'il aurait pu y êtrelargement remé-
dié. Ainsi, elle a souligné qu'aucun accord n'était intervenu quant aux

modalités d'exploitation de la centrale de GabCikovo en régimede pointe,
et a affirméque les appréhensions hongroises ne se rapportaient qu'à des
conditions d'exploitation de nature extrême.De même,elle a soutenu que
le projet initial avait déjà subi depuis 1977diverses modifications et qu'il
aurait pu être encoremodifié,par exemple en ce qui concerne le débitde
l'eau réservépour l'ancien lit du Danube ou l'alimentation des bras

secondaires par l'effet de déversoirs noyés.

45. La Slovaquie a en outre démenti avoir violéde quelque façon que
ce soit le traité de 1977 - en particulier ses articles 15 et 19 - et a
notamment fait valoir que, conformément aux termes du paragraphe 2 de

l'article3de l'accord du 6 mai 1976 relatif au plan contractuel conjoint,
les recherches concernant l'impact du projet sur l'environnement n'incom-
baient pas exclusivement à la Tchécoslovaquie, mais à l'une ou à l'autre
des parties, selon l'emplacement des ouvrages.
Enfin, elle a à son tour fait grief à la Hongrie d'avoir arrêtéses mesures
unilatérales de suspension et d'abandon des travaux en violation des dis-tion of the provisions of Article 27 of the 1977Treaty (see paragraph 18
above), which it submits required prior recourse to the machinery for dis-
pute settlement provided for in that Article.

46. The Court has no need to dwell upon the question of the applica-
bility in the present case of the Vienna Convention of 1969on the Law of
Treaties. It needs only to be mindful of the fact that it has several times

had occasion to hold that some of the rules laid down in that Convention
might be considered as a codification of existing customary law. The
Court takes the view that in many respects this applies to the provisions
of the Vienna Convention concerning the termination and the suspension
of the operation of treaties, set forth in Articles 60 to 62 (see Legal Con-
seyuencesfor States ofthe Continued Presence ofSouth Afiicu in Namibia

(South West Ajrica) not1vithstunding Security Council Resolution 276
(1970), Advisory Opinion, I.C.J. Reports. 1971, p. 47, and Fisheries
Jurisdiction (United Kingdom v. Iceland), Jurisdiction of the Court,
Judgment, I.C.J. Reports 1973, p. 18; see also Interpretation qf the
Agreement of 25 Murch 1951 hetitjeen the WHO and Egypt, Advisory

Opinion, 1.C.J. Reports 1980, pp. 95-96).
Neither has the Court lost sight of the fact that the Vienna Convention
is in any event applicable to the Protocol of 6 February 1989 whereby
Hungary and Czechoslovakia agreed to accelerate completion of the
works relating to the GabEikovo-Nagymaros Project.

47. Nor does the Court need to dwell upon the question of the rela-
tionship between the law of treaties and the law of State responsibility, to
which the Parties devoted lengthy arguments, as those two branches of
international law obviously have a scope that is distinct. A determination
of whether a convention is or is not in force, and whether it has or has
not been properly suspended or denounced, is to be made pursuant to the

law of treaties. On the other hand, an evaluation of the extent to which
the suspension or denunciation of a convention, seen as incompatible
with the law of treaties,involves the responsibility of the State which pro-
ceeded to it, is to be made under the law of state responsibility.

Thus the Vienna Convention of 1969 on the Law of Treaties confines
itself to defining- in a limitative manner - the conditions in which a
treaty may lawfully be denounced or suspended; while the effects of a
denunciation or suspension seen as not meeting those conditions are, on
the contrary, expressly excluded from the scope of the Convention by
operation of Article 73. It is moreover well established that, when a State

has committed an internationally wrongful act, its international respon-
sibility is likely to be involved whatever the nature of the obligation it
has failed to respect (cf. Interpretation of Peuce Treaties ivith Bulgaria,
Hungarp and Romania, Second Phase, Advisory Opinion, 1.C.J. Reports
1950, p. 228; and see Article 17 of the Draft Articles on State Responsi- PROJET GABC~KOVO-NAGYM (ARROEST) 38

positions de l'article 27 du traité de 1977 (voir paragraphe 18ci-dessus),
qui, d'après elle, prescrivaient le recours préalable aux mécanismes de
règlement des différends prévuspar cet article.

46. La Cour n'a pas à s'attarder sur la question de l'applicabilité en
l'espècede la convention de Vienne de 1969 sur le droit des traités. II lui
suffira de rappeler qu'à plusieurs reprises déjà elle a eu l'occasion de dire
que certaines des règles énoncéesdans ladite convention pouvaient être

considéréescomme une codification du droit coutumier existant. La Cour
est d'avis qu'à bien des égardstel est le cas des règlesde la convention de
Vienne afférentes à l'extinction et a la suspension de l'application des
traités, énoncéesa ses articles 60 à62 (voir Conséquencesjuridiquespour
les Etats de lu présence continue de I'Afiique du Sud en Namibie (Sud-

Ouest afiicain) nonobstant la résolution 276 (1970) du Conseil de sgcu-
rité,uvis consultut$ C.I.J. Recueil 1971, p. 47, et Compétenceen mutiere
de pêcheries(Roj'airme-Uni c. Islande), compétence de lu Cour, urrét,
C.I.J. Recueil 1973, p. 18; voir également Interprétation de l'accord du
25 mars 1951 entre l'OMS et I'Egypte, avis consultat$ C.I.J. Recueil

1980.,.. 95-96).
La Cour ne perd pas non plus de vue que la convention de Vienne est
en tout état de cause applicable au protocole du 6 février 1989par lequel
la Hongrie et la Tchécoslovaquie étaient convenues d'accélérerles tra-
vaux relatifs au projet Gabëikovo-Nagymaros.
47. La Cour n'a pas davantage à s'étendre surla question des relations

qu'entretiennent le droit des traités et le droit de la responsabilité des
Etats, à laquelle les Parties ont consacré de longs développements. Ces
deux branches du droit international ont en effet. à l'évidence. des
champs d'application distincts. C'est au regard du droit des traités'qu'il
convient de déterminer si une convention est ou non en vigueur, et si elle

a ou non été régulièrementsuspendue ou dénoncée.C'est en revanche au
regard du droit de la responsabilité des Etats qu'il y a lieu d'apprécier
dans quelle mesure la suspension ou la dénonciation d'une convention
qui serait incompatible avec le droit des traités engage la responsabilité
de 1'Etat qui y a procédé.

Ainsi, la convention de Vienne de 1969sur le droit des traités se borne
à définir- de façon limitative - les conditions dans lesquelles un traité
peut, de façon licite, être dénoncéou suspendu; les effets d'une dénoncia-
tion ou d'une suspension qui ne satisferait pas à ces conditions sont par
contre expressément exclusdu champ d'application de la convention par
lejeu de son article 73. Il est au demeurant bien établi que, dèslors qu'un

Etat a commis un acte internationalement illicite, sa responsabilité inter-
nationale est susceptible d'êtreengagée, quelleque soit la nature de l'obli-
gation méconnue (voir Interprktation des truitésde paix conclus avec lu
Bulgarie, la Hongrie et la Roumanie, deuxième phase, avis consultutif;
C.I.J. Recueil 1950, p. 228, et l'article 17 du projet d'articles sur la39 GABC~KOVO-NAGYM PA RJOST (JUDGMENT)

bility provisionally adopted by the International Law Commission on
first reading, Yearbook of the International Law Commission, 1980,
Vol. II,Part 2, p. 32).
48. The Court cannot accept Hungary's argument to the effect that, in
1989, in suspending and subsequently abandoning the works for which it

was still responsible at Nagymaros and at Dunakiliti, it did not, for al1
that, suspend the application of the 1977Treaty itself or then reject that
Treaty. The conduct of Hungary at that time can only be interpreted as
an expression of its unwillingness to comply with at least some of the pro-
visions of the Treaty and the Protocol of 6 February 1989, as specified in

the Joint Contractual Plan. The effect of Hungary's conduct was to
render impossible the accomplishment of the system of works that the
Treaty expressly described as "single and indivisible".
The Court moreover observes that, when it invoked the state of neces-
sity in an effort to justify that conduct, Hungary chose to place itself

from the outset within the ambit of the law of State responsibility,
thereby implying that, in the absence of such a circumstance, its conduct
would have been unlawful. The state of necessity claimed by Hungary -
supposing it to have been established- thus could not permit of the con-
clusion that, in 1989, it had acted in accordance with its obligations
under the 1977Treaty or that those obligations had ceased to be binding

upon it. It would only permit the affirmation that, under the circum-
stances, Hungary would not incur international responsibility by acting
as it did. Lastly, the Court points out that Hungary expressly acknow-
ledged that, in any event, such a state of necessity would not exempt it
from its duty to compensate its partner.

49. The Court will now consider the question of whether there was, in
1989, a state of necessity which would have permitted Hungary, without
incurring international responsibility, to suspend and abandon works
that it was committed to perform in accordance with the 1977Treaty and
related instruments.

50. Inthe present case, the Parties are in agreement in considering that
the existence of a state of necessity must be evaluated in the light of the
criteria laid down by the International Law Commission in Article 33 of
the Draft Articles on the International Responsibility of States that it
adopted on first reading. That provision is worded as follows:

"Article33. Stufe of'Necrssify

1. A state of necessity may not be invoked by a State as a ground
for precluding the wrongfulness of an act of that State not in con-
formity with an international obligation of the State unless:

(a) the act was the only means of safeguarding an essential interest
of the State against a grave and imminent peril; and PROJET GABCIKOVO-NAGYM(A ARRORET) 39

responsabilité des Etats adopté à titre provisoire par la Commission du
droit international en première lecture, Annuuire de lu Commission du
droit international, 1980,vol. II,deuxième partie, p. 30-31).
48. La Cour ne peut suivre la Hongrie lorsque celle-ci soutient qu'en
suspendant puis en abandonnant en 1989 les travaux dont elle avait

encore la charge à Nagymaros et h Dunakiliti elle n'a pas pour autant
suspendu l'application du traitéde 1977lui-même, puis rejeté ce traité. Le
comportement de la Hongrie à l'époque ne peut être interprétéque
comme traduisant sa volonté de ne pas exécuter au moins certaines dis-
positions du traité et du protocole du 6 février 1989, tellesque précisées
dans le plan contractuel conjoint. L'effet du comportement de la Hongrie

a étéde rendre impossible la réalisation du système d'ouvrages que le
traité qualifiait expressément d'«unique et indivisible)).
La Cour fera d'ailleurs observer qu'en invoquant l'état de nécessité
pour tenter de justifier ce comportement la Hongrie a choisi de se placer
d'embléesur le terrain du droit de la responsabilité des Etats, impliquant
par là qu'en l'absence d'une telle circonstance sa conduite eût étéillicite.

L'état de nécessitéalléguépar la Hongrie - à le supposer établi - ne
pourrait donc permettre de conclure qu'en 1989elle aurait agi conformé-
ment à ses obligations en vertu du traité de 1977 ou que ces obligations
auraient cesséde la lier. Ilpermettrait seulement d'affirmer que, compte
tenu des circonstances, la Hongrie n'aurait pas engagé sa responsabilité

internationale en agissant comme elle l'a fait. La Cour notera enfin que la
Hongrie a expressément reconnu qu'en tout état de cause un tel état de
nécessité nela dispenserait pas de devoir dédommager son partenaire.

49. La Cour examinera à présent la question de savoir s'il existait, en
1989, un état de nécessitéqui eût permis à la Hongrie, sans engager sa

responsabilité internationale, de suspendre et d'abandonner des travaux
qu'elle étaittenue de réaliserconformément au traité de 1977et aux ins-
truments y afférents.
50. Dans l'instance, les Parties se sont accordées pour estimer que
l'existence d'un état de nécessitédoit êtreappréciéeà la lumière des cri-

tères énoncéspar la Commission du droit international à l'article 33 du
projet d'articles sur la responsabilité internationale des Etats qu'elle a
adopté en première lecture. Cette clisposition est ainsi conçue:

((Article 33. Etat de nkcessitL;
1.L'étatde nécessité ne peut pas être invoqué parun Etat comme

une cause d'exclusion de l'illicéid'un fait de cet Etat non conforme
i une de ses obligations internationales, à moins que

a) ce fait n'ait constitué le seul moyen de sauvegarder un intérêt
essentiel dudit Etat contre un périlgrave et imminent; et que40 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

(6) the act did not seriously impair an essential interest of the State
towards which the obligation existed.
2. In any case, a state of necessity may not be invoked by a State
as a ground for precluding wrongfulness:

(a) if the international obligation with which the act of the State is
not in conformity arises out of a peremptory norm of general
international law; or
(b) if the international obligation with which the act of the State is
not in conformity is laid down by a treaty which, explicitly or
implicitly, excludesthe possibility ofinvoking the state of neces-
sity with respect to that obligation; or
(c) if the State in question has contributed to the occurrence of the
state of necessity." (Yearbook of the International Laiv Com-
mission, 1980, Vol. II, Part 2, p. 34.)

In its Commentary, the Commission defined the "state of necessity" as
being
"the situation of a State whose sole means of safeguarding an essen-
tial interest threatened by a grave and imminent peril is to adopt
conduct not in conformity with what is required of it by an interna-
tional obligation to another State" (ibid., para. 1).

It concluded that "the notion of state of necessity is . . .deeply rooted in
general legal thinking" (ibid, p. 49, para. 31).
51. The Court considers, first of all, that the state of necessity is a
ground recognized by customary international law for precluding the
wrongfulness of an act not in conformity with an international obliga-
tion. It observes moreover that such ground for precluding wrongfulness
can only be accepted on an exceptional basis. The International Law
Commission was of the same opinion when it explained that it had opted
for a negative form of words in Article 33 of its Draft

"in order to show, by this formal means also, that the case of invoca-
tion of a state of necessity as a justification must be considered as
really constituting an exception - and one even more rarely admis-
sible than is the case with the other circumstances precluding wrong-
fulness . . ."(ibid, p. 51, para. 40).

Thus, according to the Commission, the state of necessitycan only be
invoked under certain strictly defined conditions which must be cumula-
tively satisfied; and the State concerned is not the solejudge of whether
those conditions have been met.
52. In the present case, the following basic conditions set forth in
Draft Article 33 are relevant: it must have been occasioned by an "essen-
tial interest" of the State which is the author of the act conficting with
one of its international obligations; that interest must have been threat-
ened by a "grave and imminent peril"; the act being challenged must b) ce fait n'ait pas gravement porté atteinte à un intérêe tssentiel de
1'Etat à l'égardduquel l'obligation existait.
2. En tout état de cause, l'état de nécessiténe peut pas être

invoqué par un Etat comme une cause d'exclusion d'illicéité
a) si l'obligation internationale à laquelle le fait de 1'Etat n'est pas
conforme découled'une norme impérativedu droit international
général; ou

b) si l'obligation internationale a laquelle le fait de 1'Etat n'est pas
conforme est prévuepar un traité qui, explicitement ou implici-
tement, exclut la possibilité d'invoquer l'étatde nécessitéen ce
qui concerne cette obligation; ou
c) si 1'Etat en question a contribué a la survenance de l'état de
nécessité.))(Annuaire de lu Commission du droit international,

1980, vol. II,deuxième partie, p. 33.)
Dans son commentaire, la Commission a définil'«état de nécessité))
comme

«la situation où se trouve un Etat n'ayant absolument pas d'autre
moyen de sauvegarder un intérêe tssentiel menacépar un périlgrave
et imminent que celui d'adopter un comportement non conforme à

ce qui est requis de lui par une obligation internationale envers un
autre Etatn (ibid., par. 1).
Elle a conclu que: «La notion d'état de nécessitéest ... profondément

enracinée dans la théorie généraledu droit.)) (Ibid., p. 47, par. 31.)
51. La Cour considère tout d'abord que l'étatde nécessitéconstitue
une cause, reconnue par le droit international coutumier, d'exclusion de
l'illicéitéd'un fait non conforme à une obligation internationale. Elle
observe en outre que cette cause d'exclusion de l'illicéiténe saurait être
admise qu'a titre exceptionnel. Telle était aussi l'opinion de la Commis-

sion du droit international lorsqu'elle a expliqué qu'elle avait opté pour
une formule négativeà l'article 33 de son projet

«pour marquer, par cet aspect formel aussi, que l'hypothèse d'une
invocation à titre de justification de l'étatde nécessitédoit être consi-
déréecomme constituant vraiment une exception - une exception
encore plus rarement admissible que ce n'est le cas pour les autres
circonstances excluant l'illicéit..» (ibid., p. 50, par. 40).

Ainsi, d'après la Commission, l'état de nécessité nepeut être invoqué
qu'a certaines conditions, strictement définies,qui doivent être cumulati-
vement réunies; et 1'Etatconcernén'est pas seuljuge de la réunion de ces
conditions.

52. Dans la présente affaire, les conditions de base suivantes, énoncées
au projet d'article 33, sont pertinentes: un ((intérêtessentiel)) de 1'Etat
auteur du fait contraire à l'une de ses obligations internationales doit
avoir étéen cause; cet intérêtdoit avoir étémenacépar un «périlgrave et
imminent)); le fait incriminé doit avoir étéle «seul moyen)) de sauvegar-41 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

have been the "only means" of safeguarding that interest; that act must
not have "seriously impair[ed] an essential interest" of the State towards
which the obligation existed; and the State which is the author of that act
must not have "contributed to the occurrence of the state of necessity".

Those conditions reflect customary international law.
The Court will now endeavour to ascertain whether those conditions
had been met at the time of the suspension and abandonment, by Hun-
gary, of the works that it was to carry out in accordance with the 1977
Treaty.
53. The Court has no difficulty in acknowledging that the concerns

expressed by Hungary for its natural environment in the region affected
by the Gabtikovo-Nagymaros Project related to an "essential interest" of
that State, within the meaning given to that expression in Article 33 of
the Draft of the International Law Commission.

The Commission, in its Commentary, indicated that one should not, in

that context, reduce an "essential interest" to a matter only of the "exist-
ence" of the State, and that the whole question was, ultimately, to be
judged in the light of the particular case (see Yeurbook of the Internu-
tionul Luiv Commission, 1980, Vol. II, Part 2, p. 49, para. 32); at the
same time, it included among the situations that could occasion a state of
necessity, "a grave danger to . . . the ecological preservation of al1 or

some of [the] territory [of a State]" (ibid, p. 35, para. 3); and specified,
with reference to State practice, that "It is primarily in the last two
decades that safeguarding the ecological balance has come to be con-
sidered an 'essential interest' of al1States." (Ibid., p. 39, para. 14.)

The Court recalls that it has recently had occasion to stress, in thefol-
lowing terms, the great significance that it attaches to respect for the envi-
ronment, not only for States but also for the whole of mankind:

"the environment is not an abstraction but represents the living
space, the quality of life and the very health of human beings,
including generations unborn. The existence of the general obliga-
tion of States to ensure that activities within their jurisdiction and

control respect the environment of other States or of areas beyond
national control is now part of the corpus of international law relat-
ing to the environment." (Legality of the Threut or Use of Nuclear
Weapons, Advisoty Opinion, I.C. J. Reports 1996, pp. 241-242,
para. 29.)

54. The verification of the existence, in 1989, of the "peril" invoked by
Hungary, of its "grave and imminent" nature, as well as of the absence of
any "means" to respond to it, other than the measures taken by Hungary

to suspend and abandon the works, are al1complex processes. PROJET GABCIKOVO-NAGYMAROS (ARRÊT) 41

der ledit intérêt;ce fait ne doit pas avoir ((gravementporté atteinte à un
intérêt essentiel))de 1'Etat à l'égardduquel l'obligation existait; et 1'Etat
auteur dudit fait ne doit pas avoir ((contribuéa la survenance de l'étatde
nécessité)).Ces conditions reflètent le droit international coutumier.

La Cour s'emploiera maintenant iirechercher si ces conditions étaient
remplies au moment de la suspension et de l'abandon, par la Hongrie, des
travaux qu'elle devait accomplir conformément au traité de 1977.

53. La Cour ne voit aucune difficulté à reconnaître que les préoccupa-
tions exprimées par la Hongrie en ce qui concerne son environnement

naturel dans la région affectéepar le projet GabEikovo-Nagymaros
avaient trait à un «intérêtessentiel)) de cet Etat, au sens où cette expres-
sion est utiliséeà l'article 33 du projet de la Commission du droit inter-
national.
La Commission, dans son commentaire, a indiqué qu'il ne fallait pas,
dans ce contexte, réduire un ((intérêetssentiel)) de 1'Etaa sa seule «exis-

tence)), et que tout était, en définitive,question d'espèce (voir Annuuire
de lu Comtnission du droit internationul, 1980, vol. II,deuxième partie,
p. 48, par. 32); en mêmetemps, elle a mentionné, parmi les situations
susceptibles d'engendrer un état de nécessité,«un danger grave ... pour la
conservation écologique [du] territoire [d'un Etat] ou d'une partie de son
territoire))ibid, p. 34, par. 3) et a précisé, ense référantà la pratique des

Etats, que: «C'est surtout dans les deux dernières décenniesque la sau-
vegarde de l'équilibreécologique en est venue a êtreconsidéréecomme
répondant a un ((intérêtessentiel)) de tous les Etats.)) (Ibid., p. 38,
par. 14.)
La Cour rap.Allera qu'elle a récemment eu l'occasion de souligner dans
les termes suivants toite l'importance que le respect de l'environnement

revêtà son avis, non seulement pour les Etats mais aussi pour l'ensemble
du genre humain :
((l'environnement n'est pas une abstraction, mais bien l'espace où

vivent les êtreshumains et dont dépendent la qualité de leur vie et
leur santé,y compris pour les générationsà venir. L'obligation géné-
rale qu'ont les Etats de veiller ce que les activitésexercéesdans les
limites de leur juridiction ou sous leur contrôle respectent l'environ-
nement dans d'autres Etats ou dans des zones ne relevant d'aucune
juridiction nationale fait maintenant partie du corps de règles du

droit international de l'environnement.)) (Lickitéde la menuce ou de
l'emploi d'urmcs nucléuires, uvis consultatif; C.I.J. Recueil 1996,
p. 241-242, par. 29.)

54. La vérification de l'existence, en 1989, du «péril» invoqué par la
Hongrie, de son caractère «grave et imminent)), ainsi que de l'absence,
pour y faire face, detout c<moyen»autre que les mesures de suspension et
d'abandon des travaux prises par la Hongrie, constitue autant d'opéra-
tions complexes.42 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

As the Court has already indicated (see paragraphs 33 et seq.),
Hungary on several occasions expressed, in 1989,its "uncertainties" as to
the ecological impact of putting in place the GabCikovo-Nagymaros bar-
rage system, which is why it asked insistently for new scientific studies to

be carried out.

The Court considers, however, that, serious though these uncertainties
might have been they could not, alone, establish the objective existence of
a "peril" in the sense of a component element of a state of necessity. The

word "Deril" certainlv evokes the idea of "risk": that is vreciselv what
distinguishes "peril" from material damage. But a state of necessity could
not exist without a "Deril" dulv established at the relevant oint in time:
the mere apprehensi'on of a Possible "peril" could not Affice in that
remect. It could moreover hardlv be otherwise. when the "~eril" consti-
tuting the state of necessity has at the same time to be "grave" and

"imminent". "Imminence" is synonymous with "immediacy" or "proxim-
ity" and goes far beyond the concept of "possibility". As the Interna-
tional Law Commission em~hasized in its commentarv. the "ex,,emelv
grave and imminent" peril must "have been a threat to the interest at
the actual time" (Yearbook of the International Laiv Commission, 1980,
Vol. II, Part 2, p. 49, para. 33). That does not exclude, in the view of the

Court, that a "peril" appearing in the long term might be held to be
"imminent" as soon as it is established, at the relevant point in time, that
the realization of that peril, however far off it might be, is not thereby
any less certain and inevitable.
The Hungarian argument on the state of necessity could not convince
the Court unless it was at least proven that a real, "grave" and "immi-

nent" "peril" existed in 1989 and that the measures taken by Hungary
were the only possible response to it.
Both Parties have placed on record an impressive amount of scientific
material aimed at reinforcing their respective arguments. The Court has
given most careful attention to this material, in which the Parties have

developed their opposing views as to the ecological consequences of the
Project. It concludes, however, that, as will be shown below, it is not
necessary in order to respond to the questions put to it in the Special
Agreement for it to determine which of those points of view is scienti-
fically better founded.
55. The Court will begin by considering the situation at Nagymaros.

As has already been mentioned (see paragraph 40), Hungary maintained
that, if the works at Nagymaros had been carried out as planned, the
environment - and in particular the drinking water resources - in the
area would have been exposed to serious dangers on account of problems
linked to the upstream reservoir on the one hand and, on the other, the
risks of erosion of the riverbed downstream.

The Court notes that the dangers ascribed to the upstream reservoir
were mostly of a long-term nature and, above all, that they remained un-
certain. Even though the Joint Contractual Plan envisaged that the Gab- PROJET GABCIKOVO-NAGYM(A ARRORÉT) 42

Comme la Cour l'a déjàindiqué (voir paragraphes 33 et suivants), la
Hongrie a à maintes reprises fait état, en 1989, de ses ((incertitudes))
quant aux incidences écologiquesde la mise en place du système de bar-

rage de GabEikovo-Nagymaros: c'est la raison pour laquelle elle a
demandé avec insistance que de nouvelles études scientifiques soient
effectuées.
La Cour considère cependant que, quelque sérieusesqu'aient étéces
incertitudes, elles ne sauraient, à elles seules, établir l'existence objective

d'un «péril» en tant qu'élément constitutifd'un état de nécessité.Le mot
«péril» évoquecertes l'idéede «risque»; c'est précisémenten cela que le
«péril» se distingue du dommage matérialisé.Mais il ne saurait y avoir
d'état denécessitésans un «périln dûment avéréau moment pertinent; la
seule appréhension d'un «péril» possible ne saurait à cet égardsuffire. Il
pourrait d'ailleurs difficilement en aller autrement dès lors que le «péril»

constitutif de l'étatde nécessitédoit êtreà la fois (<grave»et «imminent».
L'«imminence» est synonyme d'«immédiateté» ou de «proximité» et
dépassede loin le concept d'«éventualité».Comme l'a soulignéla Com-
mission du droit international dans son commentaire. le,~ér'l((extrême-
ment grave et imminent))doit s'être«trouvé peser au moment même sur
l'intérêtmenacé)) (Annuaire de la Commission du droit international,

1980,vol. II,deuxième partie, p. 48, par. 33). Cela n'exclut pas, de l'avis
de la Cour, qu'un «péril» qui s'inscrirait dans le long terme puisse être
tenu pour (<imminent» dèslors qu'il serait établi, au moment considéré,
que la réalisation de ce péril, pour lointaine qu'elle soit, n'en serait pas
moins certaine et inévitable.

La thèse hongroise sur l'état de nécessiténe pourrait emporter la
conviction de la Cour s'il n'étaitpas au moins prouvé qu'un «péril » réel,
«grave» et «imminent» existait en 1989 et que seules les mesures prises
par la Hongrie pouvaient permettre d'y faire face.
Les deux Parties ont verséau dossier de l'affaire un impressionnant
matériel de nature scientifique à l'effet d'étayer leursthèses respectives.

La Cour a étudiétrès attentivement ce matériel, dans lequel les Parties
ont développé leurs points de vue opposés sur les conséquences écolo-
giques du projet. Elle conclut toutefois que, comme elle le montrera ci-
après, ilne lui est pas nécessaire,pour répondre aux questionsqui lui ont
étéposéesdans le compromis, de déterminer lequel de ces points de vue
est scientifiquement le plus solide.

55. La Cour se penchera d'abord sur la situation à Nagymaros. Comme
cela a déjà étémentionné (voir paragraphe 40), la Hongrie a soutenu que,
si les ouvrages de Nagymaros avaient étéréaliséscomme prévu, l'envi-
ronnement - et en particulier les ressources en eau potable - dans la
région aurait étéexposé à de graves dangers en raison, d'une part, des

problèmes liésau réservoird'amont et, d'autre part, des risques d'érosion
du lit du fleuve en aval.
La Cour constate que les dangers imputés au réservoir d'amont s'ins-
crivaient pour la plupart dans le long terme et, surtout, qu'ils demeu-
raient incertains. Même si le plan contractuel conjoint envisageait queEikovo power plant would "mainly operate in peak-load time and con-

tinuously during high water", the final rules of operation had not yet
been determined (see paragraph 19 above); however, any dangers asso-
ciated with the putting into service of the Nagymaros portion of the
Project would have been closely linked to the extent to which it was oper-
ated in peak mode and to the modalities of such operation. It follows

that, even if it could have been established - which, in the Court's
appreciation of the evidence before it, was not the case - that the reser-
voir would ultimately have constituted a "grave peril" for the environ-
ment in the area, one would be bound to conclude that the peril was not
"imminent" at the time at which Hungary suspended and then aban-

doned the works relating to the dam.

With regard to the lowering of the riverbed downstream of the Nagy-
maros dam, the danger could have appeared at once more serious and
more pressing, in so far as it was the supply of drinking water to the city

of Budapest which would have been affected. The Court would however
point out that the bed of the Danube in the vicinity of Szentendre had
already been deepened prior to 1980 in order to extract building mater-
ials, and that the river had from that time attained, in that sector, the
depth required by the 1977 Treaty. The peril invoked by Hungary had

thus already materialized to a large extent for a number of years, so that
it could not, in 1989,represent a peril arising entirely out of the project.
The Court would stress, however, that, even supposing, as Hungary
maintained, that the construction and operation of the dam would have
created serious risks, Hungary had means available to it, other than the

suspension and abandonment of the works, of responding to that situa-
tion. It could for example have proceeded regularly to discharge grave1
into the river downstream of the dam. It could likewise, if necessary, have
supplied Budapest with drinking water by processing the river water in
an appropriate manner. The two Parties expressly recognized that that

possibility remained open even though - and this is not determinative of
the state of necessity - the purification of the river water, like the other
measures envisaged, clearly would have been a more costly technique.

56. The Court now comes to the GabEikovo sector. It will recall that

Hungary's concerns in this sector related on the one hand to the quality
of the surface water in the Dunakiliti reservoir, with its effects on the
quality of the groundwater in the region, and on the other hand, more
generally, to the level, movement and quality of both the surface water

and the groundwater in the whole of the Szigetkoz, with their effects on
the Sauna and flora in the alluvial plain of the Danube (see paragraph 40
above).
Whether in relation to the Dunakiliti site or to the whole of the
Szigetkoz, the Court finds here again, that the peril claimed by Hungary
was to be considered in the long term, and, more importantly, remained

uncertain. As Hungary itself acknowledges, the damage that it appre- PROJET GAB~IKOVO-NAGYMAROS (ARRET) 43

la centrale de GabCikovo «fonctionner[ait] principalement en régime
de pointe et en mode continu lors des hautes eaux», les consignes d'ex-
ploitation définitives n'avaient pas encore été arrêtées (voilre para-
graphe 19 ci-dessus); or tout danger liéà la mise en Œuvre de la partie

du projet concernant Nagymaros aurait été étroitementdépendant de
la mesure dans laquelle et des modalités selon lesquelles il aurait été
recouru au régime de pointe. En conséquence, mêmes'il avait pu être
établi - ce que la Cour, au vu des élémentsde preuve qui lui ont été sou-
mis, n'estime pas êtrele cas - que le réservoir d'amont aurait en défi-

nitive constitué un «péril grave» pour l'environnement dans la région,
force est de conclure que ce péril n'était pas «imminent» au moment
où la Hongrie a suspendu puis abandonné les travaux afférents au bar-
rage.

Pour ce qui est de l'abaissement du lit du fleuve en'aval du barrage de
Nagymaros, le danger pouvait paraître à la fois plus grave et plus pres-
sant, dans la mesure où c'était l'alimentation en eau potable de la ville de
Budapest qui aurait étéaffectée.La Cour fera toutefois observer que le lit

du Danube dans la régionde Szentendre avait déjà étéapprofondi avant
1980 en vue d'en extraire des matériaux de construction et que le fleuve
avait dès cette époque atteint dans ce secteur la profondeur requise par le
trzitéde 1977. Le périlinvoquépar la Hongrie s'étaitainsi déjàlargement
réalisédepuis plusieurs années, si bien qu'il ne pouvait pas, en 1989,

s'agir d'un périlrésultantentièrement du projet. La Cour soulignera cepen-
dant que, à supposer que la construction et l'exploitation du barrage
auraient crééde graves risques, comme l'a soutenu la Hongrie, celle-ci
avait à sa disposition des moyens, autres que la suspension et l'abandon

des travaux, pour faire face à cette situation. Elle aurait ainsi pu pro-
céder régulièrementau déversement de gravier dans le fleuve en aval du
barrage. Elle aurait également pu, si nécessaire, pourvoir à I'alimenta-
tion de Budapest en eau potable en traitant de manière appropriée l'eau

du fleuve. Les deux Parties ont expressémentreconnu que cette possibilité
demeurait ouverte mêmesi - ce qui ne constitue pas un élémentdéter-
minant au regard de l'étatde nécessité - l'épuration des eaux du fleuve,
comme les autres mesures envisagées, aurait à l'évidenceconstitué une

technique plus coûteuse.
56. La Cour en vient maintenant au secteur de Gabtikovo. Elle rap-
pellera que les préoccupations hongroises dans ce secteur concernaient
d'une part la qualité des eaux de surface dans le réservoir de Dunakiliti,
avec ses incidences sur la qualitédes eaux souterraines dans la région,et,

d'autre part, plus généralement,le niveau, le mouvement et la qualité tant
des eaux de surface que des eaux souterraines dans l'ensemble du Szi-
getkoz, avec leurs incidences sur la faune et la flore de la plaine alluviale
du Danube (voir le paragraphe 40 ci-dessus).

Qu'il s'agisse du site de Dunakiliti ou de l'ensemble du Szigetkoz, la
Cour constate ici encore que le périlalléguépar la Hongrie s'inscrivait
dans le long terme et - élémentplus important - demeurait incertain.
Comme le reconnaît elle-mêmela Hongrie, les dommages qu'elle appré-44 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

hended had primarily to be the result of some relatively slow natural
processes, the effects of which could not easily be assessed.
Even if the works were more advanced in this sector than at Nagy-
maros, they had not been completed in July 1989 and, as the Court

explained in paragraph 34 above, Hungary expressly undertook to carry
on with them, early in June 1989. The report dated 23 June 1989 by the
ud hoc Committee of the Hungarian Academy of Sciences, which was
also referred to in paragraph 35 of the present Judgment, does not
express any awareness of an authenticated peril - even in the form of a

definite peril, whose realization would have been inevitable in the long
term - when it States that:
"The measuring results of an at least five-year monitoring period

following the completion of the Gabtikovo construction are indis-
pensable to the trustworthy prognosis of the ecological impacts of
the barrage system. There is undoubtedly a need for the establish-
ment and regular operation of a comprehensive monitoring system,
which must be more developed than at present. The examination of

biological indicatorobjects that can sensitively indicate the changes
happening in the environment, neglected till today, have to be
included."

The report concludes as follows:

"It can be stated, that the environmental, ecological and water
quality impacts were not taken into account properly during the
design and construction period until today. Because of the complex-
ity of the ecological processes and lack of the measured data and the
relevant calculations the environmental impacts cannot be evalu-
ated.

The data of the monitoring system newly operating on a very lim-
ited area are not enough to forecast the impacts probably occurring
over a longer term. In order to widen and to make the data more
frequent a further multi-year examination is necessary to decrease
the further degradation of the water quality playing a dominant role
in this question. The expected water quality influences equally the

aquatic ecosystems, the soils and the recreational and tourist
land-use."

The Court also notes that, in these proceedings, Hungary acknowledged
that, as a general rule, the quality of the Danube waters had improved
over the past 20 years, even if those waters remained subject to hyper-
trophic conditions.
However "grave" it might have been, it would accordingly have been

difficult, in the light of what is said above, to see the alleged peril as suf-
ficiently certain and therefore "imminent" in 1989.
The Court moreover considers that Hungary could, in this context PROJET GAB~IKOVO-NAGYM(A ARRORET) 44

hendait devaient résulter avant tout de processus naturels relativement
lents dont les effets ne pouvaient êtreaisément évalués.
Mêmesi les travaux étaient plus avancés dans ce secteur qu'à Nagy-

maros, ils n'étaient pas terminésen juillet 1989 et, comme la Cour l'a
exposéau paragraphe 34 ci-dessus, la Hongrie s'étaitexpressémentenga-
gée,au début du mois de juin 1989, à les poursuivre. Le rapport en date
du 23 juin 1989 du comité ad hoc de l'Académie dessciences de Hongrie,
auquel il a été fait allusionau paragraphe 35 du présent arrêt,n'exprime

pas la conscience d'un périlavéré -- pas mêmesous la forme d'un péril
précis, dont la réalisation aurait étéinéluctable dans le long terme -
lorsqu'il déclare:

«Pour prévoirde façon fiable les incidences du systèmede barrage
sur I'environnement, il est indispensable de disposer des résultats de
mesures effectuéesau cours d'une période de suivi d'au moins cinq
ans à compter de l'achèvement destravaux de construction à Gab-
Cikovo. II est sans aucun doute nécessaire de mettre en place et

d'exploiter régulièrement un systèmede suivi global, qui devrait
être beaucoup plus développéqu'à l'heure actuelle. Il conviendrait
d'y inclure l'analyse, jusqu'ici négligée,d'indicateurs biologiques
capables de révéleravec sensibilité les changements qui se pro-
duisent dans l'environnement. >)

Et le rapport de conclure:

«On peut dire que. de la périodede conception et de construction
jusqu'à ce jour, les incidences sur l'environnement, l'écologieet la
qualité de l'eau n'ont pas été correctementprises en compte. II est

impossible d'évaluer les incidences sur I'environnement en raison de
la complexité des processus écologiques ainsi que du manque de
données chiffréeset de calculs pertinents.
Les données recueillies grâce au système de suivi récemment mis
en Œuvre dans une zone très limitéene permettent pas de prévoirles

incidences qui se produiront probablement à plus long terme. Afin
de limiter toute nouvelle dégradation de la qualité de l'eau, qui joue
un rôle primordial en l'occurrence, ily a lieu de procéder à une nou-
velle analyse sur plusieurs années de manière à disposer de données
plus complètes et plus fréquentes. La qualité prévuede l'eau influe

également sur les écosystèmesaquatiques, les sols et l'utilisation de
la zone à des fins récréativeset touristiques.»
La Cour notera aussi que, dans l'instance, la Hongrie a reconnu qu'en

règle généralela qualité des eaux du Danube s'étaitamélioréeau cours
des vingt dernières années, mêmesi ces eaux restaient sujettes à des
conditions hypertrophiques.
Si «grave» qu'il eût pu être,le périlalléguépouvait difficilement, au vu
de ce qui précède, être tenu pour suffisamment certain et, dès lors,

((imminent », en 1989.
La Cour estime en outre que la Hongrie aurait là encore pu recourir à45 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

also, have resorted to other means in order to respond to the dangers that
it apprehended. In particular, within the framework of the original
Project, Hungary seemed to be in a position to control at least partially
the distribution of the water between the bypass canal, the old bed of the

Danubeand the side-arms. It should not be overlooked that the Dunakiliti
dam was located in Hungarian territory and that Hungary could con-
struct the works needed to regulate flows along the old bed of the Dan-
ube and the side-arms. Moreover, it should be borne in mind that
Article 14 of the 1977Treaty provided for the possibility that each of the

parties might withdraw quantities of water exceeding those specified in
the Joint Contractual Plan, while making it clear that, in such an event,
"the share of electric power of the Contracting Party benefiting from the
excess withdrawal shall be correspondingly reduced".
57. The Court concludes from the foregoing that, with respect to both

Nagymaros and GabCikovo, the perils invoked by Hungary, without pre-
judging their possible gravity, were not sufficiently established in 1989,
nor were they "imminent"; and that Hungary had available to it at that
time means of responding to these perceived perils other than the suspen-
sion and abandonment of works with which it had been entrusted. What

is more, negotiations were under way which might have led to a review of
the Project and the extension of some of its time-limits, without there
being need to abandon it. The Court infers from this that the respect by
Hungary, in 1989, of its obligations under the terms of the 1977 Treaty
would not have resulted in a situation "characterized so aptly by the

maxim summum jus summa injuria" (Yearbook of the International Law
Commission, 1980, Vol. II, Part 2, p. 49, para. 31).
Moreover, the Court notes that Hungary decided to conclude the 1977
Treaty, a Treaty which - whatever the political circumstances prevailing
at the time of its conclusion - was treated by Hungary as valid and in
force until the date declared for its termination in May 1992. As can be

seen from the material before the Court, a great many studies of a scien-
tific and technical nature had been conducted at an earlier time, both by
Hungary and by Czechoslovakia. Hungary was, then, presumably aware
of the situation as then known, when it assumed its obligations under the
Treaty. Hungary contended before the Court that those studies had been

inadequate and that the state of knowledge at that time was not such as
to make possible a complete evaluation of the ecological implications of
the GabCikovo-Nagymaros Project. It is nonetheless the case that
although the principal object of the 1977Treaty was the construction of
a System of Locks for the production of electricity, improvement of navi-

gation on the Danubeand protection against flooding, the need to ensure
the protection of the environment had not escaped the parties, as can be
seen from Articles 15, 19 and 20 of the Treaty.

What is more, the Court cannot fail to note the positions taken by
Hungary after the entry into force of the 1977Treaty. In 1983, Hungary

asked that the works under the Treaty should go forward more slowly, PROJET GAB~IKOVCI-NAGYM (ARROÊST) 45

d'autres moyens pour faire face aux dangers qu'elle redoutait. Dans le
cadre du projet initial, la Hongrie paraissait notamment en mesure de
contrôler au moins partiellement la répartition des eaux entre le canal de

dérivation, l'ancien lit du Danube et les bras secondaires. On ne saurait
perdre de vue que le barrage de Dunakiliti était situéen territoire hon-
grois et que la Hongrie pouvait aménager des ouvrages de régulation des
flux dans I'ancien litdu Danube et dans les bras secondaires. De plus, il
y a lieu de rappeler que l'article 14 du traité de 1977 prévoyait la possi-

bilitépour chacune des parties de prélever desquantités d'eau supérieures
à celles spécifiéesdans le plan contractuel conjoint, tout en précisant
qu'en pareil cas ((la part d'énergieélectrique revenant à la partie contrac-
tante ayant procédéaux prélèvements excédentaires sera[it] réduite en
conséquence D.
57. La Cour conclut de ce qui précèdeque, s'agissant aussi bien de

Nagymaros que de Gabëikovo, les périlsinvoqués par la Hongrie, sans
préjudice de leur gravité éventuelle, n'étaient en 1989 ni suffisamment
établis, ni ((imminents)); et que, pour y faire face, la Hongrie disposait à
l'époqued'autres moyens que la suspension et l'abandon de travaux dont
elle avait la charge. Qui plus est, des négociations étaient en cours, qui

auraient pu aboutir a une revision du projet et au report de certaines de
ses échéances,sans qu'il fût besoin de l'abandonner. La Cour en infère
que le respect par la Hongrie, en 1989, de ses obligations aux termes du
traité de 1977 n'aurait pas abouti a une situation «que l'adage summum
jus summa injuria caractérise parfaitement)) (Annuuire de lu Commission

du droit international, 1980, vol.II,deuxième partie, p. 48, par. 31).

En outre, la Cour fera observer que la Hongrie a décidéde conclure le
traité de 1977, traité qui - quelles que fussent les circonstances poli-
tiques dans lesquelles il a été conclu - a été considéré par la Hongrie
comme valide et en vigueur jusqu'à la date indiquéepour sa terminaison

en mai 1992.Comme ilressort des élémentsen possession de la Cour, de
nombreuses étudesde nature scientifique et technique avaient auparavant
étémenées, tant par la Hongrie que par la Tchécoslovaquie. On peut
donc supposer que c'était enétant consciente de la situation telle qu'elle
était alors connue que la Hongrie avait assumé ses obligations aux termes

du traité. La Hongrie a soutenu devant la Cour que ces étudesavaient été
insuffisantes et que l'étatdes connaissances à l'époque ne permettait pas
d'évaluer pleinement les incidences écologiques du projet Gabëikovo-
Nagymaros. 11n'en reste pas moins que, bien que le traité de 1977 eût
pour principal objet la construction d'un système d'éclusespour la produc-
tion d'électricité,l'amélioration de la navigation sur le Danube et la pro-

tection contre les inondations, la nécessitéd'assurer la protection de I'en-
vironnement n'avait pas échappé aux parties, ainsi qu'en témoignent les
articles 15, 19 et 20 du traité.
De surcroît, la Cour ne peut manquer de noter les positions adoptées
par la Hongrie après l'entrée en vigueurdu traité de 1977. En 1983, la

Hongrie a sollicité le ralentissement des travaux prescrits par le traité,46 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

for reasons that were essentially economic but also, subsidiarily, related
to ecological concerns. In 1989, when, according to Hungary itself, the
state of scientific knowledge had undergone a significant development, it
asked for the works to be speeded up, and then decided, three months
later, to suspend them and subsequently to abandon them. The Court is
not however unaware that profound changes were taking place in Hun-

gary in 1989, and that, during that transitory phase, it might have been
more than usually difficult to co-ordinate the different points of view pre-
vailing from time to time.
The Court infers from al1these elements that, in the present case, even
if it had been established that there was. in 1989, a state of necessity
linked to the performance of the 1977 Treaty, Hungary would not have

been permitted to rely upon that state of necessity in order to justify its
failure to comply with its treaty obligations, as it had helped, by act or
omission to bring it about.
58. It follows that the Court has no need to consider whether Hun-
gary, by proceeding as it did in 1989, "seriously impair[ed] an essential
interest" of Czechoslovakia, within the meaning of the aforementioned
Article 33 of the Draft of the International Law Commission - a finding

which does not in any way prejudge the damage Czechoslovakia claims
to have suffered on account of the position taken by Hungary.
Nor does the Court need to examine the argument put forward by
Hungary, according to which certain breaches of Articles 15 and 19 of
the 1977 Treaty, committed by Czechoslovakia even before 1989, con-
tributed to the purported state of necessity; and neither does it have to

reach a decision on the argument advanced by Slovakia, according to
which Hungary breached the provisions of Article 27 of the Treaty,
in 1989, by taking unilateral measures without having previously
had recourse to the machinery of dispute settlement for which that
Article provides.

59. In the light of the conclusions reached above, the Court, in reply to
the question put to it in Articl2, paragraph 1 (a), of the Special Agree-
ment (see paragraph 27 above), finds that Hungary was not entitled to
suspend and subsequently abandon, in 1989, the works on the Nagy-
maros Project and on the part of the GabEikovo Project for which the
1977 Treaty and related instruments attributed responsibility to it.

60. By the terms of Article 2, paragraph 1 (h),of the Special Agree-
ment, the Court is asked in the second place to decide

"(6) whether the Czech and Slovak Federal Republic was entitled
to proceed, in November 1991, to the 'provisional solution' PROJET GABC~KOVO-NAGYMAROS (ARRET) 46

pour des raisons essentiellement économiques mais aussi, subsidiaire-
ment, écologiques. En 1989,alors que, selon la Hongrie elle-même, l'état
des connaissances scientifiques avait sensiblement évolué,lle a sollicité
l'accélérationdesdits travaux, pour décider ensuite,trois mois plus tard,

de les suspendre, puis de les abandonner. La Cour n'en ignore pas pour
autant que de profonds changements étaienten cours en Hongrie en 1989
et que, pendant cette phase transitoire,l pouvait s'avérerbien plus dif-
ficilequ'à l'ordinaire de coordonner les différents pointsde vues qui pré-
valaientà divers moments.
La Cour infèrede tous ces éléments qu'enl'espèce,mêmes'ilavait été
établiqu'il existaiten 1989un état de nécessité liél'exécutiondu traité
de 1977,la Hongrie n'aurait pas été admise à s'en prévaloirpour justifier
le manquement à ses obligations conventionnelles, car elle aurait contri-
bué,par action ou omission, à sa survenance.

58. En conséquence,la Cour n'ii pas à examiner la question de savoir

si,en procédant commeelle l'a fait en 1989,la Hongrie aurait ((gravement
porté atteinteà un intérêtessentiel)) de la Tchécoslovaquie,au sens de
l'article3 susmentionnédu projet de la Commission du droit internatio-
nal; cette constatation ne saurait en rien préjuger desdommages que la
Tchécoslovaquieaffirme avoir subis du fait de la position hongroise.
La Cour n'a pas davantage à se pencher sur l'argument présentépar la
Hongrie, suivant lequel certaines violations des articles 15et 19du traité
de 1977, commises par la Tchécoslovaquie dèsavant 1989, auraient
concouru à I'étatde nécessitéallégué; etelle n'a pas non plusà se pro-
noncer sur l'argument avancépar la Slovaquie, selon lequel la Hongrie
aurait violé lesdispositions de l'article 27 du traité,en 1989,en prenant
des mesures unilatérales sans avoir au préalable eu recours aux méca-

nismes de règlementdes différendsprévus à cet article.

59. Au vu des conclusions auxquelles elle est parvenue ci-dessus, la
Cour répond à la question qui lui a étéposéeà l'article 2, paragraphe 1,
alinéa a),du compromis (voir ci-dessus paragraphe 27) que la Hongrie
n'était pasen droit de suspendre puis d'abandonner, en 1989,les travaux
relatifs au projet de Nagymaros ainsi qu'à la partie du projet de Gab-
ëikovo dont elle était responsable aux termes du traité de 1977 et des
instruments y afférents.

60. Aux termes de l'article 2,paragraphe 1, alinéab), du compromis,
il est demandéen second lieu àla Courde dire

«b) si la Républiquefédérativetchèque es tlovaque étaiten droit de
recourir, en novembre 1991, à la «solution provisoire)) et de GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

and to put into operation from October 1992 this system,
described in the Report of the Working Group of Independent
Experts of the Commission of the European Communities, the
Republic of Hungary and the Czech and SlovakFederal Repub-

lic dated 23 November 1992 (damming up of the Danube at
river kilometre 1851.7 on Czechoslovak territory and resulting
consequences on water and navigation course)".

61. The Court will recall that, as soon as Hungary suspended the
works at Nagymaros on 13 May 1989 and extended that suspension to
certain works to be carried out at Dunakiliti, Czechoslovakia informed
Hungary that it would feel compelled to take unilateral measures if Hun-

gary were to persist in its refusa1to resume the works. This was inter alia
expressed as follows in Czechoslovakia's Note Verbale of 30 October
1989 to which reference is made in paragraph 37 above:

"Should the Republic of Hungary fail to meet its liabilities and
continue unilaterally to breach the Treaty and related legal docu-
ments then the Czechoslovak party will be forced to commence a

provisional, substitute project on the territory of the Czechoslovak
Socialist Republic inorder to prevent further losses. Such a provi-
sional project would entail directing as much water into the Gab-
tikovo dam as agreed in the Joint Construction Plan."

As the Court has already indicated (see paragraph 23), various
alternative solutions were contemplated by Czechoslovakia. In Septem-
ber 1990, the Hungarian authorities were advised of seven hypothetical

alternatives defined by the firm of Hydroconsult of Bratislava. All of
those solutions implied an agreement between the parties, with the excep-
tion of one variant, subsequently known as "Variant C", which was pre-
sented as a provisional solution which could be brought about without
Hungarian CO-operation. Other contacts between the parties took place,
without leading to a settlement of the dispute. In March 1991, Hungary

acquired information according to which perceptible progress had been
made in finalizing the planning of Variant C; it immediately gave expres-
sion to the concern this caused.
62. Inter-governmental negotiation meetings were held on 22 April
and 15 July 1991.
On 22 April 1991, Hungary proposed the suspension, until September

1993, of al1 the works begun on the basis of the 1977 Treaty, on the
understanding that the parties undertook to abstain from any unilateral
action, and that joint studies would be carried out in the interval.
Czechoslovakia maintained its previous position according to which the
studies contemplated should take place within the framework of the 1977
Treaty and without any suspension of the works.

On 15July 1991,Czechoslovakia confirmed its intention of putting the PROJET GABCIKOVO-NAGYM(A ARP.RET) 47

mettre en service, à partir d'octobre 1992, ce système, décrit
dans le rapport en date du 23 novembre 1992du groupe de tra-
vail d'experts indépendants nommés par la Commission des

Communautés européennes, la République de Hongrie et la
République fédérative tchèqueet slovaque (construction d'un
barrage sur le Danube au kilomètre 1851,7 du fleuve, en terri-
toire tchécoslovaque, et conséquences en résultant pour I'écou-
lement des eaux et la navigation))).

61. La Cour rappellera que, dèsque la Hongrie a suspendu les travaux
à Nagymaros le 13 mai 1989 et a étendu cette suspension à certains tra-

vaux qui devaient êtreréalisésà Dunakiliti, la Tchécoslovaquie a informé
la Hongrie qu'elle se verrait contrainte de prendre des mesures unilaté-
rales si cette dernière persistait dans son refus de reprendre les travaux.
Cela fut notamment exprimé de 1;ifaçon suivante dans la note verbale
tchécoslovaque en date du 30 octobre 1989,à laquelle il est fait référence
au paragraphe 37 ci-dessus:

«Si la République de Hongrie ne s'acquittait pas de ses responsa-

bilitéset continuaità enfreindre unilatéralement les dispositions du
traité et des documents juridiques y afférents, la partie tchécoslo-
vaque se verrait contrainte d'entreprendre à la place un projet pro-
visoire sur son territoire pour éviter de nouvelles pertes. Ce projet
provisoire conduirait à diriger vers le barrage de Gabtikovo toute la
quantité d'eau convenue dans le plan de construction conjoint. »

Comme la Cour l'a déjà indiqué(voir paragraphe 23), différentessolu-

tions de rechange furent envisagées par la Tchécoslovaquie. En sep-
tembre 1990, les autorités hongroises furent aviséesdes sept hypothèses
définies par la firme Hydroconsult de Bratislava. Toutes ces solutions
impliquaient un accord entre les parties, à l'exception d'une variante,
dénomméepar la suite ((variante CD, qui était présentéecomme une
solution provisoire pouvant être réaliséesans la coopération de la Hon-

grie. D'autres contacts entre les parties eurent lieu sans conduire à une
solution du différend. En mars 1991, la Hongrie entra en possession
d'informations selon lesquelles la mise au point de la planification de
la variante C avait sensiblement progressé; elle fit aussitôt connaître les
craintes que cela lui inspirait.
62. Des réunions intergouvernementales de négociation se tinrent le

22 avril et le 15juillet 191.
Le 22 avril 191,la Hongrie proposa la suspension,jusqu'en septembre
1993,de tous les travaux commencéssur la base du traité de 1977, étant
entendu que les parties s'engageraient à s'abstenir de toute action unila-
térale et que des études communes seraient menéesdans l'intervalle. La
Tchécoslovaquie maintint sa position antérieure selon laquelle les études

envisagéesdevraient avoir lieu dans le cadre du traitéde 1977et sans sus-
pension des travaux.
Le 15juillet 1991, la Tchécoslo~aquieconfirma son intention de mettre48 GAB~IKOVO-NAGYMAROS PROJECT (JUDGMENT)

GabEikovo power plant into service and indicated that the available data
enabled the effects of four possible scenarios to be assessed, each of them
requiring the co-operation of the two Governments. At the same time, it
proposed the setting up of a tripartite committee of experts (Hungary,
Czechoslovakia, European Communities) which would help in the search
for technical solutions to the problems arising from the entry into opera-
tion of the GabCikovo sector. Hungary, for its part, took the view that :

"In the case of a total lack of understanding the so-called C varia-
tion or 'theoretical opportunity' suggested by the Czecho-Slovak
party as a unilateral solution would besuch a grave transgression of
Hungarian territorial integrity and International Law for which
there is no precedent even in the practices of the formerly socialist
countries for the past 30 years";

it further proposed the setting up of a bilateral committee for the assess-
ment of environmental consequences, subject to work on Czechoslovak
territory being suspended.
63. By a letter dated 24 July 1991,the Government of Hungary com-
municated the following message to the Prime Minister of Slovakia:
"Hungarian public opinion and the Hungarian Government

anxiously and attentively follows the [Czechoslovakian] press reports
of the unilateral steps of the Government of the Slovak Republic
in connection with the barrage system.
The preparatory works for diverting the water of the Danube near
the Dunakiliti dam through unilaterally are also alarming. These
steps are contrary to the 1977Treaty and to the good relationship
between our nations."

On 30 July 1991 the Slovak Prime Minister informed the Hungarian
Prime Minister of
"the decision of the Slovak Government and of the Czech and Slo-
vak Federal Government to continue work on the GabEikovo power
plant, as a provisional solution, which is aimed at the commence-
ment of operations on the territory of the Czech and Slovak Federal
Republic".

On the same day, the Government of Hungary protested, by a Note Ver-
bale, against the filling of the headrace canal by the Czechoslovak con-
struction Company, by pumping water from the Danube.
By aletter dated 9 August 1991and addressed to the Prime Minister of
Slovakia, the Hungarian authorities strenuously protested against "any
unilateral step that would be in contradiction with the interests of our
[two]nations and international law" and indicated that they considered it
"very important [to] receive information as early as possible on the PROJET GABCIKOVO-NAGYM(A ARRRSÉT) 48

en service la centrale de GabEikovo et indiqua que les données dispo-
nibles permettaient d'évaluer les effets de quatre scénarios d'exploitation
possibles requérant chacun la coopération des deux gouvernements. En
même temps,elle proposa la constitution d'un comité d'experts tripartite

(Hongrie, Tchécoslovaquie, Communautés européennes) qui aiderait a
trouver des solutions techniques aux problèmes résultant de la mise en
exploitation du secteur de GabEikovo. La Hongrie, quant à elle, exposa
que :

«Dans le cas où on ne parviendrait absolument pas à s'entendre,
la solution dite variantC ou ((possibilitéthéorique)), proposée par
la partie tchécoslovaque en tant que solution unilatérale, constitue-
rait une atteinte grave à l'intégritéterritoriale de la Hongrie et au

droit internationaldont il n'existe aucun précédent mêmd eans la
pratique des anciens pays socialistes au cours des trente dernières
années» ;

elle proposa par ailleurs de constituer un comité bipartited'évaluation
des incidences écologiques, sous réserveque les travaux soient suspendus
en territoire tchécoslovaque.
63. Par lettre en date du 24 juillet 1991, le Gouvernement hongrois
communiqua au premier ministre slovaque le message suivant:

((L'opinion publique hongroise et le Gouvernement hongrois sui-
vent avec inquiétude et attention les nouvelles publiéesdans la presse
[tchécoslovaque]sur les mesures unilatérales prises par le Gouverne-

ment de la République slovaque concernant le système de barrage.
Les travaux préparatoires entrepris au voisinage du barrage de
Dunakiliti pour détourner unilatéralement les eaux du Danube ont
également de quoi inquiéter. Ces mesures vont à l'encontre des dis-
positions du traité de 1977 et sont préjudiciables aux relations de

bon voisinage entre nos pays.>)
Le 30 juillet 1991, le premier ministre slovaque informa le premier mi-
nistre hongrois de

«la décisiondu Gouvernement slovaque et du Gouvernement de la
République fédérative tchèque et slovaquede poursuivre les travaux

de construction de la centrale de GabEikovo,a titre de solution pro-
visoire, en vue de permettre sa mise en service sur le territoire de la
République fédérative tchèque etslovaque».

Le mêmejour, le Gouvernement hongrois protesta, par note verbale,
contre la mise en eau du canal d'amenéeréaliséepar l'entreprise tchéco-
slovaque de construction en pompant de l'eau du Danube.
Par lettre du 9 août 1991, adressée au premier ministre slovaque, les
autorités hongroises s'élevèrent vivement((contre toute mesure unilaté-
rale allant à I'encontre des intérêts[des deux] pays ainsi que du droit

international)) et indiquèrent qu'elles considéraient ((comme très impor-
tant d'êtreinformé[es]dès que possible des détails de la solution provi-49 GABC~KOVO-NAGYM PROJOCT (JUDGMENT)

details of the provisional solution".For its part, Czechoslovakia, in a
Note Verbale dated 27 August 1991, rejected the argument of Hungary
that the continuation of the works under those circumstances constituted
a violation of international law, and made the following proposal:

"Provided the Hungarian side submits a concrete technical solu-
tion aimed at putting into operation theabtikovo system of locks

and a solution of the system of locks based on the 1977 Treaty in
force and the treaty documents related to it, the Czechoslovak side is
prepared to implement the mutually agreed solution."

64. The construction permit for Variant C was issued Gn 30 October
1991.In November 1991construction of a dam started at Cunovo, where
both banks of the Danube are on Czechoslovak (now Slovak) territory.

In the course of a new inter-governmental negotiation meeting, on

2 December 1991, the parties agreed to entrust the task of studying the
whole of the question of the Gabtikovo-Nagymaros Project to a Joint
Expert Committee which Hungary agreed should be complemented with
an expert from the European Communities. However whereas, for Hun-
gary,the work of that Committee would have been meaningless if Czecho-

slovakia continued construction of Variant C, for Czechoslovakia, the
suspension of the construction, even on a temporary basis, was unaccept-
able.
That meeting was followed by a large number of exchanges of letters
between the parties and various meetings between their representatives at

the end of 1991 and earlv in 1992. On 23 Januarv 1992. Czechoslovakia
expressed its readiness "to stop work on the provisional solution and
continue the construction upon mutual agreement" if the tripartite com-
mittee of experts whose constitution it proposed, and the results of the
test operation of the GabCikovo part, were to "confirm that negative eco-
logical effects exceed its benefits". However, the positions of the parties

were by then comprehensively defined, and would scarcely develop any
further. Hungary considered, as it indicated in a Note Verbale of 14 Feb-
ruary 1992, that Variant C was in contravention

"of [the Treaty of 19771. . . and the convention ratified in 1976
regarding the water management of boundary waters.

.............................
with the principles of sovereignty, territorial integrity, with the
inviolability of State borders, as well as with the general customary
norms on international rivers and the spirit of the 1948 Belgrade
Danube Convention" ;

and the suspension of the implementation of Variant C was, in its view, a
prerequisite. As for Czechoslovakia, it took the view that recourse to
Variant C had been rendered inevitable, both for economic and ecologi-soire)). Pour sa part, la Tchécoslovaquie, dans une note verbale en date
du 27 août 1991, rejeta l'argument hongrois selon lequel la poursuite des
travaux dans ces conditionsconstituait une violation du droit internatio-
nal et fit la proposition suivante:

«Pourvu que la partie hongroise apporte une solution technique
concréte en vue de la mise en service du système d'éclusesde Gab-
Cikovo et une solution pour Itsystème d'éclusesfondéesur le traité

de 1977en vigueur et sur les actes conventionnels y afférents,la par-
tie tchécoslovaque est prêteà exécuterla solution arrêtéed'un com-
mun accord. »
64. Le permis de construire de la variante C fut délivréle 30 octobre

k991. En novembre 1991, la construction d'un barrage commença à
Cunovo, où les deux rives du Danube se trouvent en territoire tchéco-
slovaque (aujourd'hui slovaque).
Au cours d'une nouvelle réunion intergouvernementale de négociation,
le 2 décembre 1991, les parties s'accordèrent pour confier l'étude de

l'ensemble de la question du projet GabCikovo-Nagymaros à un comité
mixte d'experts auquel la Hongrie accepta d'associer un expert des Com-
munautés européennes. Mais alors que, pour la Hongrie, le travail dudit
comité aurait étédépourvu de sens si la Tchécoslovaquie poursuivait la
construction de la variante C, pour la Tchécoslovaquie, une interruption,
mêmeprovisoire, des travaux étaitinacceptable.

Cette réunion fut suivie de nombreux échanges de correspondances
entre les parties et de diverses rencontres entre leurs représentants à la fin
de l'année1991 et au début de 1992. Le 23janvier 1992,la Tchécoslova-
quie se dit prête<(àarrêterses travaux afférentsà la solution provisoire et
à poursuivre la construction [qui serait]convenue d'un commun accord))

si le comitéd'experts tripartite dont elle proposait la constitution et les
résultats de l'essai d'exploitation de l'élémentde GabCikovo «confir-
m[ai]ent que les effets écologiques défavorables dépass[ai]ent les avan-
tages recueillis». Toutefois, les positions des parties étaient alors globa-
lement arrêtées, etne devaient plus guère évoluer. La Hongrie estimait,
comme elle l'a indiqué dans une note verbale du 14 février 1992, que la

variante C était contraire
«aux dispositions du [traitéde 19771... comme acelles de la conven-
tion ratifiée en 197sur la réglementationen matière d'eauxfrontières.

aux principes de souveraineté et d'intégritéterritoriale, à I'inviolabi-
litédes frontières d'Etat ainsi qu'aux règles coutumières générales

relatives aux fleuves internationaux et à l'esprit de la convention de
Belgrade de 1948 sur le Danube» ;
et la suspension de l'exécutionde la variante C était pour elle un préa-

lable. Quant à la Tchécoslovaquie, elle considérait que le recours à la
variante C avait étérendu inévitable,pour des raisons tant économiquescal as well as navigational reasons, because of the unlawful suspension
and abandonment by Hungary of the works for which provision was
made in the 1977 Treaty. Any negotiation had, in its view, to be con-
ducted within the framework of the Treaty and without the implementa-
tion of Variant C - described as "provisional" - being called into

question.
65. On 5 August 1992,the Czechoslovak representative to the Danube
Commission informed it that "work on the severance cutting through of
the Danube's flow will begin on 15 October 1992 at the 1,851.759-kilo-
metre line" and indicated the measures that would be taken at the time of
the "severance". The Hungarian representative on the Commission pro-

tested on 17 August 1992, and called for additional explanations.
During the autumn of 1992, the implementation of VariantvC was
stepped up. The operations involved in damming the Danube at Cunovo
had been scheduled by Czechoslovakia to take place during the second
half of October 1992,at a time when the waters of the river are generally
at their lowest level. On the initiative of the Commission of the European

Communities, trilateral negotiations took place in Brussels on 21 and
22 October 1992, with a view to setting up a committee of experts and
defining its terms of reference. On that date, the first phase of the opera-
tions leading to the damming of the Danube (the reinforcement of the
riverbed and the narrowing of the principal channel) had been com-
pleted. The closure of the bed was begun on 23 October 1992 and the

construction of the actual dam continued from 24 to 27 October 1992:
a pontoon bridge was built over the Danube on Czechoslovak territory
using river barges, large Stones were thrown into the riverbed and
reinforced with concrete, while 80 to 90 per cent of the waters of the
Danube were directed into the canal designed to supply the Gabtikovo
power plant. The implementation of Variant C did not, however, come

to an end with the diversion of the waters, as there still remained out-
standing both reinforcement work on the dam and the building of certain
auxiliary structures.
The Court has already referred in paragraph 24 to the meeting
held in London on 28 October 1992 under the auspices of the European
Communities, in the course of which the parties to the negotiations

agreed, inter dia, to entrust a tripartite Working Group composed of
independent experts (Le., four experts designated by the European Com-
mission, one designated by Hungary and another by Czechoslovakia)
with the task of reviewing the situation created by the implementation of
Variant C and making proposals as to urgent measures to adopt. After

having worked for one week in Bratislava and one week in Budapest, the
Working Group filed its report on 23 November 1992.
66. A summary description of the constituent elements of Variant C
appears at paragraph 23 of the present Judgment. For the purposes of
the question put to the Court, the officia1 description that should be
adopted is, according to Article 2, paragraph 1 (b), of the Special Agree-
ment, the one given in the aforementioned report of the Working Group PROJET GABCIKOVO-NAGYM(A ARRRSET) 50

qu'écologiques etde navigation, dri fait de la suspension et de l'abandon
illicites, par la Hongrie, des travaux prévus par le traité de 1977; toute
négociation devait, selon elle, se poursuivre dans le cadre du traitéet sans
que l'exécutionde la variante C - qualifiéede «provisoire» - soit mise

en cause.

65. Le 5 août 1992,le représentant tchécoslovaque à la commission du
Danube informa celle-ci que «les travaux de fermeture du Danube com-
mencer[aient] le 15octobre 1992au point kilométrique 1851,759» et indi-

qua les mesures qui seraient prises au moment de la fermeture. Le repré-
sentant hongrois à la commission protesta le 17août 1992, en réclamant
plus d'explications.
Pendant l'automne 1992, I'exécutionde la variante C s'accéléra.Les
opérations de barrage du Danube à Cunovo avaient étéprévues par la
Tchécoslovaquie pour la seconde moitié du mois d'octobre 1992, à un

moment où les eaux du fleuve sont en généralà leur niveau le plus bas. A
l'initiative de la Commission des (~ommunautéseuropéennes, des négo-
ciations trilatérales eurent lieu à Bruxelles les 21 et 22 octobre 1992 en
vue de mettre en place un comité d'experts et de définirson mandat. A
cette date, la première phase des opérations de barrage du Danube (ren-

forcement du lit du fleuve et réduction de la largeur du chenal principal)
était achevée. La fermeture du lit fut amorcée le 23 octobre 1992 et la
construction du barrage proprement dit se poursuivit du 24 au 27 octobre
1992: un pont flottant fut aménagésur le Danube en territoire tchéco-
slovaque au moyen de péniches,de grosses pierres furent déverséesdans

le lit de la rivière et recouvertes de béton, tandis que quatre-vingts à
quatre-vingt-dix pour cent des eaux du Danube étaient dirigéesdans le
canal destiné à l'alimentation de la centrale de Gabëikovo. L'exécution
de la variante C n'étaitcependant pas terminéeavec le détournement des
eaux car il restait encore à effectuer des travaux de consolidation du bar-
rage et à construire certains ouvrages auxiliaires.

La Cour a déjàévoquéau paragraphe 24 la réunion tenue a Londres le
28 octobre 1992 sous les auspices des Communautés européennes, au
cours de laquelle les parties aux négociations convinrent notamment
de charger un groupe de travail tripartite d'experts indépendants (soit

quatre experts désignéspar la Commission européenne,un expert désigné
par la Hongrie et un autre désignépar la Tchécoslovaquie) d'étudier la
situation crééepar la mise en Œuvre de la variante C et de faire des pro-
positions sur les mesures d'urgence à adopter. Après avoir travaillé une
semaine à Bratislava et une semaine à Budapest, le groupe de travail
déposa son rapport le 23 novembre 1992.

66. Il a été procédé à une description sommaire des élémentsconstitu-
tifs de la varianteC au paragraphe 23 du présent arrêt. Aux fins de la
question poséeà la Cour, la description officielle à retenir est, selon I'ar-
ticle 2, paragraphe 1, alinéab), du compromis, celle qu'en fait le rapport
susmentionné du groupe de travail d'experts indépendants; il y a lieu de51 GAB~IKOVO-NAGYMAROS PROJECT (JUDGMENT)

of independent experts, and it should be emphasized that, according to
the Special Agreement, "Variant C" must be taken to include the conse-

quences "on water and navigation course" of the dam closing off the bed
of the Danube.
In the section headed "Variant C Structures and Status of Ongoing
Work", one finds, in the report of the W.orking Group, the following
passage :

"In both countries the original structures for the GabEikovo
scheme are completed except for the closure of the Danube river at
Dunakiliti and the
(1) Completion of the hydropower station (installation and testing

of turbines) at GabEikovo.
Variant C consists of a complex of structures, located in Czecho-
Slovakia . . .The construction of these are planned for two phases.
The structures include . . :

(2) By-pass weir controlling the flow into the river Danube.
(3) Dam closing the Danubian river bed.
(4) Floodplain weir (weir in the inundation).
(5) lntake structure for the Mosoni Danube.
(6) lntake structure in the power canal.
(7) Earth barragesidykes connecting structures.

(8) Ship lock for smaller ships (1 5 m x 80 m).
(9) Spillway weir.
(10) Hydropower station.
The construction of the structures 1-7 are included in Phase 1,
while the remaining 8-10 are a part of Phase 2 scheduled for con-

struction 1993-1995."

67. Czechoslovakia had maintained that proceeding to Variant C and
putting it into operation did not constitute internationally wrongful acts;
Slovakia adopted this argument. During the proceedings before the Court
Slovakia contended that Hungary's decision to suspend and subsequently
abandon the construction of works at Dunakiliti had made it impossible
for Czechoslovakia to carry out the works as initially contemplated by

the 1977Treaty and that the latter was therefore entitled to proceed with
a solution which was as close to the original Project as possible. Slovakia
invoked what it described as a "principle of approximate application" to
justify the construction and operation of Variant C. It explained that this
was the only possibility remaining to it "of fulfilling not only the pur-
poses of the 1977Treaty, but the continuing obligation to implement it in
good faith".

68. Slovakia also maintained that Czechoslovakia was under a duty to
mitigate the damage resulting from Hungary's unlawful actions. It claimed PROJET GABCIKOVO-NAGYMAROS (ARRÈT) 51

souligner par ailleurs que, d'après le compromis, la ((variante CD doit
êtrecomprise comme incluant les conséquences «pour l'écoulement des

eaux et la navigation))qui résultentdu barrage fermant le lit du Danube.

Sous le point intitulé ((Ouvrages de la variante C et étatd'avancement
des travaux)), on trouve, dans le rapport du groupe de travail, le passage
suivant :

«Dans les deux pays, les ouvrages prévus à l'origine dans le pro-
gramme de Gabëikovo sont achevés,à l'exception de la fermeture du
Danube à Dunakiliti ainsi que:
1) les derniers travaux de la centrale hydro-électrique (installation

et essais des turbines) de Gabëikovo.
La variante C est un ensemble complexe d'ouvrages, situé en
Tchécoslovaquie ... La construction de ces ouvrages est prévue en
deux phases. Les ouvrages cornprennent ..:

2) lesdéversoirsdedérivationcontrôlant l'écoulementdans leDanube;
3) le barrage fermant le lit du Danube;
4) le déversoirde la plaine d'inondation;
5) l'ouvrage de prise alimentant le bras Moson du Danube;
6) l'ouvrage de prise alimentant le canal usinier;

7) les barragesldigues en terre reliant les ouvrages;
8) l'éclusedestinée aux navires de faible tonnage (15 m x 80 m);
9) l'évacuateur de crue;
10) la centrale hydro-électrique.
La construction des ouvrages 1a 7 est prévuependant la phase 1,
tandis que les ouvrages 8 à 10 relèvent de la phase 2 prévue pour

1993-1995.))

67. La Tchécoslovaquie avait soutenu que le recours à la variante C et
la mise en service de celle-ci ne constituaient pas des faits internationale-
ment illicites; la Slovaquie a repris cette thèse. Au cours de la procédure
devant la Cour, la Slovaquie a affirméque la décisionde la Hongrie de
suspendre puis d'abandonner la construction des ouvrages à Dunakiliti

avait mis la Tchécoslovaquie dans l'impossibilité d'effectuerles travaux
tels qu'ils avaient initialement été envisagéspar le traité de 1977 et que
cette dernière était en conséquenceen droit de recourir à une solution qui
était aussi proche que possible du projet initial. La Slovaquie a invoqué
ce qu'ellea décritcomme un ((principe d'application par approximation))
pour justitier la construction et la mise en service de la varianC. Elle a
expliqué que c'étaitla la seule possibilité qui lui restait «non seulement

d'atteindre les buts viséspar le traité de 1977, mais encore de respecter
l'obligation continue de mettre en Œuvre ledit traité de bonne foi».
68. La Slovaquie a aussi soutenu que la Tchécoslovaquie avait l'obli-
gation d'atténuer les dommages résultant des agissements illicites de la52 GABC~KOVO-NAGYM PAORJCST(JUDGMENT)

that a State which is confronted with a wrongful act of another State is

under an obligation to minimize its losses and, thereby, the damages
claimable against the wrongdoing State.It arguedfurthermore that "Miti-
gation of damages is also an aspect of the performance of obligations in
good faith." For Slovakia, these damages would have been immense in
the present case, given the investments made and the additional economic

and environmental prejudice which would have resulted from the failure
to complete the works at DunakilitiiGabEikovo and to put the system
into operation. For this reason, Czechoslovakia was not only entitled,
but even obliged, to implement Variant C.

69. Although Slovakia maintained that Czechoslovakia's conduct was
lawful, it argued in the alternative that, even were the Court to find
otherwise, the putting into operation of Variant C could still be justified
as a countermeasure.

70. Hungary for its part contended that Variant C was a material
breach of the 1977 Treaty. It considered that Variant C also violated
Czechoslovakia's obligations under other treaties, in particular the Con-
vention of 31 May 1976 on the Regulation of Water Management Issues
of Boundary Waters concluded at Budapest, and its obligations under
general international law.

71. Hungary contended that Slovakia's arguments rested on an erro-
neous presentation of the facts and the law. Hungary denied, inter alia,
having committed the slightest violation of its treaty obligations which
could have justified the putting into operation of Variant C. It considered
that "no such rule" of "approximate application" of a treaty exists in

international law; as to the argument derived from "mitigation of dam-
age[s]", it claimed that this has to do with the quantification of loss, and
could not serve to excuse conduct which is substantively unlawful. Hun-
gary furthermore stated that Variant C did not satisfy the conditions
required by international law for countermeasures, in particular the con-

dition of proportionality.

72. Before dealing with the arguments advanced by the Parties, the
Court wishes to make clear that it is aware of theerious problems with

which Czechoslovakia was confronted as a result of Hungary's decision
to relinquish most of the constructionof the System of Locks for which
it was responsible by virtue of the 1977 Treaty. Vast investments had
been made, the construction at GabEikovo was al1 but finished, the
bypass canal was completed, and Hungary itself, in 1991, had duly ful-

filled its obligations under the Treaty in this respect in completing work
on the tailrace canal. It emerges from the report, dated 31 October 1992,
of the tripartite fact-finding mission the Court has referred to in para-
graph 24 of the present Judgment, that not using the system would have PROJET GABC~KOVO-NAGYMAROS (ARRET) 52

Hongrie. Elle a alléguéqu'un Etat qui se trouve confronté au fait illicite
d'un autre Etat est tenu de limiter ses pertes au minimum, et de réduire
ainsi les dommages et intérêtssusceptibles d'êtreréclamésà 1'Etat auteur
du fait illicite. Elle a en outre exposéque: ((L'atténuation des dommages
est aussi un aspect de l'exécutiondes obligations de bonne foi.)) Pour la
Slovaquie, les dommages et intérêtsauraient en l'occurrence été considé-
rables, compte tenu des investissements effectués et des préjudices sup-

plémentaires, tant de nature économique qu'écologique, qui auraient
résultéde l'inachèvement des travaux à DunakilitilGabtikovo et du
défaut de mise en service du systèn~e.C'est pourquoi la Tchécoslovaquie
était non seulement en droit, mais encore dans l'obligation, de mettre en
Œuvre la variante C.
69. Bien que la Slovaquie affirme que le comportement de la Tché-

coslovaquie était licite, elle a soutenu à titre subsidiaire que, même
si la Cour devait conclure dans un autre sens, la mise en service de la va-
riante C pourrait encore êtrejustifiéeen tant que contre-mesure.
70. La Hongrie, pour sa part, a soutenu que la variante C consti-
tue une violation substantielle du traitéde 1977. Elle considère que la va-
riante C viole aussi les obligations de la Tchécoslovaquie en vertu d'autres

traités, notamment la convention sur la réglementation en matière
d'eaux frontières, conclue à Budapest le 31 mai 1976, et ses obligations
au titre du droit international général.
71. La Hongrie a prétendu que l'argumentation slovaque reposait sur
une présentation erronéedes faits et du droit. La Hongrie nie notamment
avoir commis la moindre violation de ses obligations conventionnelles
qui aurait pu justifier la mise en Œuvre de la variante
C. Elle estime qu'il
n'existe «aucune règle» d'«application par approximation » d'un traité
en droit international; quant à l'argument tiréde ((l'atténuationdes dom-
mages)), elle fait valoir qu'il a trait à l'appréciation du préjudice et ne
saurait servir à excuser un comportement illicite sur le fond. La Hongrie
expose en outre que la variante C rie satisfait pas aux conditions requises
par le droit international en matière de contre-mesures, et en particulier

la condition de proportionnalité.

72. Avant d'examiner les arguments que les Parties ont ainsi avancés,la
Cour souhaite indiquer clairement qu'elle est consciente des sérieuxpro-

blèmes auxquels la Tchécoslovaquie a dû faire face à la suite de la déci-
sion prise par la Hongrie de renoncerà la plus grande partie de la construc-
tion du systèmed'éclusesqui lui incombait en vertu du traitéde 1977.Des
investissements trèsimportants avaient été effectuélsa, construction de I'ou-
vrage de Gabtikovo était pratiquement achevée,le canal de dérivation était
terminé,et la Hongrie elle-même,en 1991,s'étaitdûment acquittée deses

obligations à cet égarden achevant les travaux du canal de fuite. II ressort
du rapport, en date du 31 octobre 1992,de la mission d'enquêtetripartite a
laquelle la Cour s'est référéeu paragraphe 24 du présentarrêt quela non-53 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

led to considerable financial losses, and that it could have given rise to
serious problems for the environment.
73. Czechoslovakia repeatedly denounced Hungary's suspension and
abandonment of works as a fundamental breach of the 1977 Treaty and

consequently could have invoked this breach as a ground for terminating
the Treaty; but this would not have brought the Project any nearer to
completion. It therefore chose to insist on the implementation of the
Treaty by Hungary, and on many occasions called upon the latter to
resume performance of its obligations under the Treaty.

When Hungary steadfastly refused to do so - although it had expressed
its willingness to pay compensation for damage incurred by Czechoslo-
vakia - and when negotiations stalled owing to the diametrically opposed
positions of the parties, Czechoslovakia decided to put the GabEikovo
system into operation unilaterally, exclusively under its own control and

for its own benefit.
74. That decision went through various stages and, in the Special
Agreement, the Parties asked the Court to decide whether Czecho-
slovakia "was entitled to proceed, in November 1991" to Variant C,
and "to put [it] into operation from October 1992".

75. With a view to justifying those actions, Slovakia invoked what it
described as "the principle of approximate application", expressed by
Judge Sir Hersch Lauterpacht in the following terms:

"lt is a sound principle of law that whenever a legal instrument of
continuing validity cannot be applied literally owing to the conduct of
one of the parties, it must, without allowing that party to take advan-
tage of its own conduct, be applied in a way approximating most

closely to its primary object. To do that is to interpret and to give
effect to the instrument - not to change it." (Adrrzissibilituf Heur-
ings of Petitioners by the Committee on Soutlz West Africu, I.C.J.
Reports 1956, separate opinion of Sir Hersch Lauterpacht, p. 46.)

It claimed that this is a principle of international law and a general prin-
ciple of law.
76. It is not necessary for the Court to determine whether there is a

principle of international law or a general principle of law of "approxi-
mate application" because, even if such a principle existed, it could by
definition only be employed within the limits of the treaty in question. In
the view of the Court, Variant C does not meet that cardinal condition
with regard to the 1977 Treaty.

77. As the Court has already observed, the basic characteristic of the
1977 Treaty is, according to Article 1, to provide for the construction of
the Gabcikovo-Nagymaros System of Locks as a joint investment con-
stituting a single and indivisible operational system of works. This
element is equally reflected in Articles 8 and 10 of the Treaty providing

for joint ownership of the most important works of the GabEikovo-
Nagymaros Project and for the operation of this joint property as a
CO-ordinated single unit. By definition al1 this could not be carried PROJET GABCIKOVO-NAGYM(A ARORSET) 53

utilisation du systèmeaurait causé despertes financièresconsidérableset
qu'elle aurait pu entraîner de graves problèmes pour l'environnement.
73. La Tchécoslovaquie a maintes fois indiqué que la suspension et
l'abandon des travaux par la Hongrie constituaient une violation essentielle
du traitéde 1977et elle aurait pu par conséquent invoquercelle-cicomme

motif de mettre fin au traité;mais cela n'aurait en rien fait avancer le projet
vers son achèvement.C'est pourquoi elle a préféré insister pour que la Hon-
grie mette en Œuvrele traite et a demandéa de nombreuses reprises a celle-ci
de reprendre l'exécutiondes obligations lui incombant en vertu du traité.
Lorsque la Hongrie a résolument refuséde s'exécuter - bien qu'elle

eût exprimé sa volonté d'indemniser la Tchécoslovaquie pour les dom-
mages subis - et lorsque les négociations sont arrivéesau point mort du
fait des positions diamétralement opposées des parties, la Tchécoslova-
quie a décidéde mettre unilatéralement en service le système de Gab-
fikovo, sous son contrôle et a son profit exclusifs.

74. Cette décision acomporté plusieurs étapes et, dans le compromis,
les Parties ont demandé a la Cour de dire si la Tchécoslovaquie «était en
droit de recourir, en novembre 1901 >)à la variante C et «de mettre en
service [cette dernière], à partir d'octobre 1992)).
75. En vue de justifier ces actions, la Slovaquie a invoqué ce qu'elle a
décrit comme <(le principe d'application par approximation)) tel

qu'exprimépar sir Hersch Lauterpacht dans les termes suivants:
«C'est un principe sain de droit que si un instrument juridique de

validité continue ne peut s'appliquer littéralement, du fait de la
conduite de l'une des parties, il faut, sans permettre A celle-ci de se
prévaloir de sa propre conduite, l'appliquer d'une manière s'appro-
chant le plus possible de son but primitif. Agir ainsi est interpréter et
donner effet a l'instrument et non le modifier.)) (Admissihiliti de

l'audition depititionnaires purle Comitédu Sut]-Ouest africrrin, C.1J.
Recueil 1956, opinion individuelle de sir Hersch Lauterpacht, p. 46.)

Elle a prétendu qu'il s'agit d'un principe du droit international et d'un
principe généralde droit.
76. La Cour n'a pas à déterminer s'il existe un principe de droit inter-
national ou un principe généralde droit d'«application par approxima-
tion)) car, mêmesi un tel principe existait, il ne pourrait par définition y
êtrerecouru que dans les limites du traité en cause. Or, de l'avis de la

Cour, la variante C ne satisfait pas à cette condition primordiale au
regard du traité de 1977.
77. Comme la Cour l'a déjà observé,la caractéristique fondamentale
du traitéde 1977est, selon son article premier, de prévoirla construction
du système d'éclusesde Gabcikovo-Nagymaros en tant qu'investissement

conjoint constituant un système d'ouvrages opérationnel, unique et indi-
visible. Cet élément estégalementreflétéaux articles 8 et 10 du traité, qui
prévoient la propriété conjointedes ouvrages les plus importants du pro-
jet Gabfikovo-Nagymaros et l'exploitationde cette propriétéconjointe
comme une entité unique et coordonnée. Par définition, tout cela ne pou- 54 GABCIKOVO-NAGYMAROS PROJECT (JCDGMENT)

out by unilateral action. In spite of having a certain external physical

similarity with the original Project, Variant C thus differed sharply from
it in its legal characteristics.
78. Moreover, in practice, the operation of Variant C led Czechoslo-
vakia to appropriate, essentially for its use and benefit, between 80 and
90 per cent of the waters of the Danube before returning them to the

main bed of the river, despite the fact that the Danube is not only a
shared international watercourse but also an international boundary
river.
Czechoslovakia submitted that Variant C was essentially no more than
what Hungary had already agreed to and that the only modifications
made were those which had become necessary by virtue of Hungary's

decision not to implement its treaty obligations. It is true that Hungary,
in concludingthe 1977Treaty, had agreed to the damming of the Danube
and the diversion of its waters into the bypass canal. But it was only in
the context of a joint operation and a sharing of its benefits that Hungary
had given its consent. The suspension and withdrawal of that consent
constituted a violation of Hungary's legal obligations, demonstrating, as

it did, the refusal by Hungary of joint operation; but that cannot mean
that Hungary forfeited its basic right to an equitable and reasonable
sharing of the resources of an international watercourse.

The Court accordingly concludes that Czechoslovakia, in putting
Variant C into operation, was not applying the 1977 Treaty but, on the

contrary, violated certain of its express provisions, and, in so doing,
committed an internationally wrongful act.
79. The Court notes that between November 1991and October 1992,
Czechoslovakia confined itself to the execution, on its own territory, of
the works which were necessary for the implementation of Variant C, but

which could have been abandoned if an agreement had been reached
between the parties and did not therefore predetermine the final decision
to be taken. For as long as the Danube had not been unilaterally
dammed, Variant C had not in fact been applied.
Such a situation is not unusual in international law or, for that matter,
in domestic law. A wrongful act or offence is frequently preceded by pre-

paratory actions which are not to be confused with the act or offence
itself. It is as well to distinguish between the actual commission of a
wrongful act (whether instantaneous or continuous) and the conduct
prior to that act which is of a preparatory character and which "does
not qualify as a wrongful act" (see for example the Commentary on
Article 41 of the Draft Articles on State Responsibility, "Report of the

International Law Commission on the work of its forty-eighth session,
6 May-26 July 1996", Officiul Records ofthe General Assemblj>, Fifty-
first Session, Supplemcnt No. 10 (AlSlilO), p. 141, and Yearbook of the
International Law Commission, 1993, Vol. II, Part 2, p. 57, para. 14). PROJET GABCIKOVO-NAGYM(A ARRRSET) 54

vait êtreréalisépar voie d'action unilatérale. En dépit d'une certaine res-
semblance physique extérieure avecle projet initial, la varianteC en dif-
fèredonc nettement quant à ses caractéristiquesjuridiques.
78. De plus, dans la pratique, la mise en service de la variante C a
conduit la Tchécoslovaquie à s'approprier, essentiellement pour son usage
et à son profit, entre quatre-vingts et quatre-vingt-dix pour cent des eaux

du Danube avant de les restituer iiülit principal du fleuve, en dépit du
fait que le Danube est non seulement un cours d'eau international par-
tagé mais aussi un fleuve frontière.
La Tchécoslovaquie a soutenu que la variante C, pour l'essentiel, n'est
rien d'autre que ce à quoi la Hongrie avait déji consenti et que seules ont
étéeffectuéesles modifications rendues nécessairespar suite de la déci-

sion de la Hongrie de ne pas exécuterses obligations conventionnelles. II
est vrai que la Hongrie, en concluant le traité de 1977, avait accepté le
barrag" du Danube et le détournement de ses eaux dans le canal de déri-
vation. Mais c'était seulementdans le contexte d'une opération conjointe
et d'un partage de ses bénéficesque la Hongrie avait donné son consen-

tement. La suspension et le retrait de ce consentement ont constitué une
violation par la Hongrie de ses obligations juridiques, montrant effecti-
vement que celle-ci a refuséune exploitation conjointe; mais il ne saurait
s'ensuivre que la Hongrie aurait perdu son droit fondamental à une part
équitable et raisonnable des ressources d'un cours d'eau international.
La Cour conclut en conséquence que la Tchécoslovaquie, en mettant

en service la variante C, n'a pas appliqué le traité de 1977 mais, au
contraire, a violécertaines de ses dispositions expresses et, de ce fait, a
commis un acte internationalement illicite.
79. La Cour note qu'entre novembre 1991 et octobre 1992 la Tchéco-
slovaquie s'est bornée iexécutersur son propre territoire des travaux qui
étaientcertes nécessairespour la mise en Œuvrede la variante C, mais qui

auraient pu êtreabandonnés si un accord était intervenu entre les parties
et ne préjugeaient dès lors pas de la décision définitiveà prendre. Tant
que le Danube n'avait pas étébarréunilatéralement, la variante C n'avait
en fait pas été appliquée.
Une telle situation n'est pas rare en droit international, comme d'ailleurs
en droit interne. Un fait illicite ou une infraction est fréquemmentprécédée

d'actes préparatoires quine sauraient êtreconfondus avec le fait ou l'infrac-
tion eux-mêmes.Il convient de distinguer entre la réalisation même'un fait
illicite (que celui-ci soit instantanéou continu) et le comportement antérieur
à ce fait qui présenteun caractère préparatoireet «qui ne saurait être traité
comme un fait illicite))(voir par exsmple le commentaire de l'article 41 du
projet d'articles sur la responsabilité desEtacRapport de la Commission

du droit international sur lestravaux de sa quarante-huitième session,6 mai-
26 juillet 1996», Docun~rntsojjcieis (le l'A.ssrmblèegbnèrale,cinquante et
uniènîeses.rion,suppl<;mennt o/O (A/51/1O),p. 164,et Annuaire de lu Con>-
mission du droit intrrnutional, 1993,volII,deuxièmepartie, p. 59, par. 14).55 GAB~IKOVO-NAGYMAROS PROJECT (JUDGMENT)

80. Slovakia also maintained that it was acting under a duty to miti-
gate damages when it carried out Variant C. It stated that "It is a general
principle of international law that a party injured by the non-perform-
ance of another contract party must seek to mitigate the damage he has
sustained."
It would follow from such a principle that an injured State which has

failed to take the necessary measures to limit the damage sustained would
not be entitled to claim compensation for that damage which could have
been avoided. While this principle might thus provide a basis for the cal-
culation of damages, it could not, on the other hand, justify an otherwise
wrongful act.
81. Since the Court has found that the putting into operation of Vari-

ant C constituted an internationally wrongful act, the duty to mitigate
damage invoked by Slovakia does not need to be examined further.

82. Although it did not invoke the plea of countermeasures as a
primary argument, since it did not consider Variant C to be unlawful,
Slovakia stated that "Variant C could be presented as a justified
countermeasure to Hungary's illegal acts".

The Court has concluded, in paragraph 78 above, that Czechoslovakia
committed an internationally wrongful act in putting Variant C into
operation. Thus, it now has to determine whether such wrongfulness may
be precluded on the ground that the measure so adopted was in response
to Hungary's prior failure to comply with its obligations under interna-

tional law.
83. In order to be justifiable, a countermeasure must meet certain con-
ditions (see Militurq und Paramilitary Acti~,itie.sin und uguinst Nicara-
gua jNicaraguu v. United Stute~ of Anwrica) , Merits, Judgment, 1.C.J.
Reports 1986. p. 127, para. 249. See also Arbitral Abvardoj 9 Dccrmher
19711in the case concerning the Air Service Agreement oj 27 Murch 1946

betwern the Unitrd States oj America and France, United Nations,
Reports of lnternutionul Arbitral A)t,ards (RIAA), Vol. XVIII, pp. 443 et
seq.; also Articles 47 to50 of the Draft Articles on State Responsibility
adopted by the International Law Commission on first reading, "Report
of the International Law Commission on the work of its forty-eighth ses-
sion, 6 May-26 July 1996", Ofjciul Records of the General Assembly,

Fifty-Jirst Session, Supplement No. 10 (A/51110),pp. 144-145.)

In the first place it must be taken in response to a previous interna-
tional wrongful act of another State and must be directed against that
State. Although not primarily presented as a countermeasure, it is clear
that Variant C was a response to Hungary's suspension and abandon- PROJET GABCIKOVCI-NAGYMAROS (ARRET) 55

80. La Slovaquie a aussi soutenu que son action était motivéepar une

obligation d'atténuer des dommages lorsqu'elle a réaliséla variante C.
Elle a déclaréque ((c'est un principe de droit international qu'une partie
léséedu fait de la non-exécution d'un engagement pris par une autre par-
tie doit s'employer à atténuer les dommages qu'elle a subis)).
Il découlerait d'un tel principe qu'un Etat léséqui n'a pas pris les
mesures nécessaires a l'effet de limiter les dommages subis ne serait pas

en droit de réclamer l'indemnisation de ceux qui auraient pu êtreévités.
Si ledit principe pourrait ainsi fournir une base pour le calcul de dom-
mages et intérêts,en revanche, il rie saurait justifier ce qui constitue par
ailleurs un fait illicite.
81. La Cour ayant conclu que la mise en service de la variante C
a constitué un fait internationalement illicite, l'obligation d'atténuer

les dommages invoquée par la Slovaquie n'a pas a êtreexaminée plus
avant.

82. Bien qu'elle n'ait pas fait valoir à titre principal l'argumentation

tiréedes contre-mesures. puisqu'elle neconsidère pas la varianteC comme
illicite. la Slovaquie a déclaréque <<lavariante C pourrait être considérée
comme une contre-mesure justifiée en réponse aux actes illicites de la
Hongrie ».
La Cour, au paragraphe 78 ci-dessus, est parvenue i la conclusion que
la Tchécoslovaquie a commis un acte internationalement illicite en met-

tant en service la varianteC. Illui faut donc aprésent rechercher si cette
illicéitpeut êtreexcuséeau motif que la mesure ainsi adoptée l'aurait été
en réaction au défaut préalable de la Hongrie de s'acquitter de ses obli-
gations en vertu du droit international.
83. Pour pouvoir être justifiée.une contre-mesure doit satisfaire à cer-
taines conditions (voir Activitks rnilifuires et purumilitui~~esau Nir.urugutr

et contre celui-ci (Nicrrruguu c. Etuts-Unis d'A~n~;ri(~ilef)o,nd. urrêt,
C.I.J. Recueil 1986, p. 127, par. 249. Voir aussi Sentence rirhitrule clu
9 d6crrnbrc~1978 cn luffi~irc coricerrlunt /'(record rrlttf uus .servic~s
ukriens I/L27 rn~~r.1~946 entrr /es Etcrf.s-Unisd'Anli.rique rt la Fruncc,
Nations Unies, Recueil (les sentcJnces arbitrales (RSA), vol. XVI II,
p. 483 et suiv., et articles A750 di1 projet d'articles sur la responsabilité

des Etats adopté par la Commission du droit international en première
lecture, ((Rapportde la Commission du droit international sur les tra-
vaux de sa quarante-huitième session, 6 mai-26 juillet 1996», Docur?ierits
c?~ficiede 1I'A.s.seinblkgec;r~éruc,inquante et unic;mesession, .s~lpplPr~ent
n" 10 (A/5l/lO), p. 167-168.)
En premier lieu, elle doit êtreprise pour riposter à un fait internatio-
nalement illicite d'un autre Etat et doit êtredirigéecontre ledit Etat. Bien

qu'elle n'ait pasétéprésentéeà titre principal comme une contre-mesure,
il est clair que la variante C a constitué une ripostiila suspension et àment of works and that it was directed against that State; and it is
equally clear, in the Court's view, that Hungary's actions were interna-
tionally wrongful.
84. Secondly, the injured State must have called upon the State com-
mitting the wrongful act to discontinue its wrongful conduct or to make
reparation for it. It is clear from the facts of the case, as recalled above by

the Court (see paragraphs 61 et seq.), that Czechoslovakia requested
Hungary to resume the performance of its treaty obligations on many
occasions.
85. In the view of the Court, an important consideration is that the
effects of a countermeasure must be commensurate with the injury suf-

fered, taking account of the rights in question.
In 1929, the Permanent Court of International Justice, with regard to
navigation on the River Oder, stated as follows:

"[the] community of interest in a navigable river becomes the basis
of a common legal right, the essential features of which are the per-

fect equality of al1riparian States in the user of the whole course of
the river and the exclusion of any preferential privilege of any one
riparian State in relation to the others" (Territorial Jurisdiction of
the International Commission of the River Oder, Judgment No. 16,
1929, P.C.I.J., Series A, No. 23, p. 27).

Modern development of international law has strengthened this prin-
ciple for non-navigational uses of international watercourses as well, as
evidenced by the adoption of the Convention of 21 May 1997on the Law
of the Non-Navigational Uses of International Watercourses by the
United Nations General Assembly.

The Court considers that Czechoslovakia, by unilaterally assuming
control of a shared resource, and thereby depriving Hungary of its right
to an equitable and reasonable share of the natural resources of the Dan-
ube - with the continuing effects of the diversion of these waters on the
ecology of the riparian area of the Szigetkoz - failed to respect the pro-
portionality which is required by international law.

86. Moreover, as the Court has already pointed out (see para-
graph 78), the fact that Hungary had agreed in the context of the original
Project to the diversion of the Danube (and, in the Joint Contractual
Plan, to a provisional measure of withdrawal of water from the Danube)
cannot be understood as having authorized Czechoslovakia to proceed
with a unilateral diversion of this magnitude without Hungary's consent.

87. The Court thus considers that the diversion of the Danube carried
out by Czechoslovakia was not a lawful countermeasure because it was
not proportionate. It is therefore not required to pass upon one other
condition forthe lawfulness of a countermeasure, namely that its purpose
must be to induce the wrongdoing State to comply with its obliga-l'abandon des travaux par la Hongrie et qu'elle était dirigéecontre cet
Etat; et il est tout aussi clair, de l'avis de la Cour, que les agissements de
la Hongrie étaient internationalement illicites.
84. En second lieu, 1'Etatlésé doit avoir invité1'Etatauteur du fait illi-
cite à mettre fin à son comportement illicite ou à en fournir réparation. Il

ressort clairement des faits de la cause, tels que rappelésci-dessus par la
Cour (voir paragraphes 61 et suivants), que la Tchécoslovaquie, à de
nombreuses reprises, a prié la Hongrie de reprendre l'exécution de ses
obligations conventionnelles.
85. De l'avis de la Cour, une condition importante est que les effets

d'une contre-mesure doivent être proportionnés aux dommages subis
compte tenu des droits en cause.
En 1929, la Cour permanente de Justice internationale, à propos de la
navigation sur I'Oder, a déclaréce qui suit:

(([la]communauté d'intérêtssur un fleuve navigable devient la base
d'une communauté de droit, dont les traits essentiels sont la parfaite
égalitéde tous les Etats riverains dans l'usage de tout le parcours

du fleuve et l'exclusion de tout privilège d'un riverain quelconque
par rapport aux autres)) (Juridiction trr'ritorialc de la Commission
internationale de I'Oder. arrêtno 16, 1929, C.P.J.I. série A no 23,
p. 27).

Le développement moderne du droit international a renforcé ce prin-

cipe également pour les utilisations des cours d'eau internationaux à des
fins autres que la navigation, comme en témoigne l'adoption par 1'Assem-
bléegénéraledes Nations Unies, le 21 mai 1997, de la convention sur le
droit relatif aux utilisations des cours d'eau internationaux à des fins
autres que la navigation.
La Cour considère que la Tchécoslovaquie, en prenant unilatéralement

le contrôle d'une ressource partagée, et en privant ainsi la Hongrie de son
droit à une part équitable et raisonnable des ressources naturelles du
Danube -- avec les effets continus que le détournement de ses eaux
déploiesur l'écologiede la région riveraine du Szigetkoz - n'a pas res-
pectéla proportionnalité exigéepar le droit international.

86. Par ailleurs, comme la Cour l'a déjà relevéci-dessus (voir para-
graphe 78), le fait que la Hongrie ait consenti, dans le cadre du projet
initial, au détournement du Danube (et, dans le plan contractuelconjoint,
à titre provisoire à des prélèvementsd'eau dans le Danube) ne saurait
s'interpréter comme ayant autorisé la Tchécoslovaquie a procéder à un
détournement unilatéral de cette importance sans le consentement de la

Hongrie.
87. La Cour estime donc que le détournement du Danube effectuépar
la Tchécoslovaquie n'étaitpas une contre-mesure licite, faute d'êtrepro-
portionnée. Elle n'a dès lors pas à statuer sur une autre condition dont
dépend la licéitéd'une contre-mesure, à savoir que celle-ci doit avoir
pour but d'inciter 1'Etat auteur du fait illicite à exécuter les obligations57 GAB~~KOVO-NAGYMAROSPROJECT (JUDGMENT)

tions under international law, and that the measure must therefore be
reversible.

88. In the light of the conclusions reached above, the Court, in reply to
the question put to it in Article 2, paragraph 1 (h), of the Special Agree-
ment (see paragraph 60), finds that Czechoslovakia was entitled to pro-
ceed, in November 1991, to Variant C in so far as it then confined itself

to undertaking works which did not predetermine the final decision to be
taken by it. On the other hand, Czechoslovakia was not entitled to put
that Variant into operation from October 1992.

89. By the terms of Article 2, paragraph 1 (c), of the Special Agree-
ment, the Court is asked, thirdly, to determine "what are the legal effects
of the notification, on 19 May 1992, of the termination of the Treaty by
the Republic of Hungary".

The Court notes that it has been asked to determine what are the legal
effects of the notificatioG drivenon 19Mav 1992of the termination of the
Treaty. It will consequently confine itself to replying to this question.
90. The Court will recall that, by early 1992, the respective parties to
the 1977Treaty had made clear their positions with regard to the recourse

by Czechoslovakia to Variant C. Hungary in a Note Verbale of 14 Feb-
ruary 1992had made clear its view that Variant C was a contravention of
the 1977Treaty (see paragraph 64 above); Czechoslovakia insisted on the
implementation of Variant C as a condition for further negotiation. On
26 February 1992, in a letter to his Czechoslovak counterpart, the Prime

Minister of Hungary described the impending diversion of the Danube as
"a serious breach of international law" and stated that, unless work was
suspended while further enquiries took place, "the Hungarian Govern-
ment [would] have no choice but to respond to this situation of necessity
by terminating the 1977 inter-State Treaty". In a Note Verbale dated
18March 1992,Czechoslovakia reaffirmed that, while it was prepared to

continue negotiations "on every level", it could not agree "to stop al1
work on the provisional solution".

On 24 March 1992, the Hungarian Parliament passed a resolution

authorizing the Government to terminate the 1977 Treaty if Czechoslo-
vakia did not stop the works by 30 April 1992. On 13 April 1992, the
Vice-President of the Commission of the European Communities wrote
to both parties confirming the willingness of the Commission to chair a
committee of independent experts including representatives of the two
countries, in order to assist the two ~overnments in identifying a mutu- PROJET GABCIKOVO-NAGYM(A ARORSÊT) 57

qui lui incombent en droit international, et que la mesure doit partant
êtreréversible.

88. Au vu des conclusions auxquelles elle est parvenue ci-dessus, la
Cour répond à la question qui lui a étéposéeà l'article 2, paragraphe 1,
alinéa b), du compromis (voir paragraphe 60) que la Tchécoslovaquie
était en droit de recourir, en novembre 1991, à la variante C, dans la
mesure où elle se bornait alorsà entamer des travaux qui ne préjugeaient
pas de la décision définitive qu'elledevait prendre. En revanche, la Tché-

coslovaquie n'étaitpas en droit de mettre en service cette variante à partir
d'octobre 1992.

89. Aux termes de l'article 2, paragraphe 1,alinéac), du compromis, il

est demandé à la Cour en troisième lieu de dire «quels sont les effetsjuri-
diques de la notification, le 19mai 1992,de la terminaison du traitépar la
République de Hongrie)).
La Cour relèvera qu'il luia étédemandé de déterminer les effets juri-
diques de la notification de terminaison du traité effectuéeà la date du
19 mai 1992. Elle se bornera en conséquence à répondre à cette question.

90. La Cour rappellera que, début 1992, les parties au traité de 1977
avaient clairement fait connaître leurs positions respectives sur le recours
par la Tchécoslovaquie à la variante C. Dans une note verbale du
14 février 1992, laHongrie avait fait savoir qu'elle considérait que la
variante C contrevenait au traité de 1977 (voir paragraphe 64 ci-dessus);
la Tchécoslovaquie faisait de la mise en Œuvrede la variante C une condi-

tion de toute nouvelle négociation. Le 26 février 1992, dans une lettre à
son homologue tchécoslovaque, le premier ministre hongrois décrivit le
détournement imminent du Danube comme «une grave violation du
droit international)) et affirma qu'Amoins que les travaux ne soient sus-
pendus pendant la réalisation de nouvelles études «le Gouvernement
hongrois n'aura[it] d'autre choix, pour faire face Licette situation de

nécessité,que de mettre fin au traité interétatique de 1977)). Dans une
note verbale du 18mars 1992, la Tchécoslovaquie réaffirma que, tout en
étant disposée a poursuivre les négociations(( Aous les niveaux)), elle ne
pouvait pas accepter ((d'arrêterles travaux afférents à la solution provi-
soire)).
Le 24 mars 1992, le Parlement hongrois adopta une résolution par
laquelle il autorisait le gouvernement à mettre fin au traité de 1977 si la

Tchécoslovaquie n'avait pas cesséles travaux au 30 avril 1992.Le 13avril
1992, le vice-présidentde la Commission des Communautés européennes
écrivitaux deux parties pour leur confirmer que la Commission était dis-
poséeà présiderun comitéd'experts indépendants, comprenant des repré-
sentants des deux pays, en vue d'aider les deux gouvernements à dégager58 GABC~KOVO-NAGYM PAOROCT (JUDGMENT)

ally acceptable solution. Commission involvement would depend on each
Government not taking "any steps . . . which would prejudice possible
actions to be undertaken on the basis of the report's findings". The

Czechoslovak Prime Minister stated in a letter to the Hungarian Prime
Minister dated 23 April 1992,that his Government continued to be inter-
ested in the establishment of the proposed committee "without any pre-
liminary conditions"; criticizing Hungary's approach, he refused to sus-
pend work on the provisional solution, but added, "in my opinion, there

is still time, until the damming of the Danube (Le., until October 31,
1992),for resolving disputed questions on the basis of agreement of both
States".

On 7 May 1992,Hungary, in the very resolution in which it decided on

the termination of the Treaty, made a proposal, this time to the Slovak
Prime Minister, for a six-month suspension of work on Variant C. The
Slovak Prime Minister replied that the Slovak Government remained
ready to negotiate, but considered preconditions "inappropriate".

91. On 19 May 1992, the Hungarian Government transmitted to the

Czechoslovak Government a Declaration notifying it of the termination
by Hungary of the 1977Treaty as of 25 May 1992. In a letter of the same
date from the Hungarian Prime Minister to the Czechoslovak Prime
Minister, the immediate cause for termination was specified to be Czecho-
slovakia'srefusal, expressed in its letter of 23 April 1992, to suspend the

work on Variant C during mediation efforts of the Commission of the
European Communities. In its Declaration, Hungary stated that it could
not accept the deleterious effects for the environment and the conserva-
tion of nature of the implementation of Variant C which would be prac-
tically equivalent to the dangers caused by the realization of the original

Project.It added that Variant C infringed numerous international agree-
ments and violated the territorial integrity of the Hungarian State by
diverting the natural course of the Danube.

92. During the proceedings, Hungary presented five arguments in sup-
port of the lawfulness, and thus the effectiveness, of its notification of
termination. These were the existence of a state of necessity; the impos-
sibility of performance of the Treaty; the occurrence of a fundamental
change of circumstances; the material breach of the Treaty by Czecho-

slovakia; and, finally, the development of new norms of international
environmental law. Slovakia contested each of these grounds.
93. On the first point, Hungary stated that, as Czechoslovakia had
"remained inflexible" and continued with its im~lementation of Variant
C, "a temporary state of necessity eventually became permanent, justify-

ing termination of the 1977 Treaty".
Slovakia, for its part, denied that a state of necessity existed on the PROJET GABC~KOVO-NAGYMAROS (ARRET) 5 8

une solution qu'ils puissent tous deux accepter. La participation de la
Commission était subordonnée à la condition que les deux gouverne-
ments s'abstiennent de prendre «des mesures susceptibles de porter
atteinte aux actions qu'il pourrait y avoir lieu d'entreprendre sur la base

des conclusions du rapport)). Le premier ministre tchécoslovaque, dans
une lettre du 23 avril 1992 adressée au premier ministre hongrois, fit
savoir que son gouvernement était toujours intéressé,((sans conditions
préalables)),à la constitution du comité envisagé;critiquant l'attitude de
la Hongrie, il refusait de suspendre les travaux relatifs à la solution pro-
visoire, mais ajoutait: ((selon moi, d'ici le barrage du Danube (c'est-

à-dire d'ici au 31 octobre 1992), il reste du temps pour résoudre les
questions litigieuses sur la base d'un accord entre les deux Etatsn.
Le 7 mai 1992, la Hongrie, dans la résolution mêmeou elle prenait la
décision de mettre fin au traité, proposa, cette fois au premier ministre
slovaque, une suspension de six mois des travaux relatifs à la variante C.
Le premier ministre slovaque répondit que le Gouvernement slovaque

était toujours prêtà négocier, mais qu'il considérait ((inapproprié)) de
poser des conditions préalables.
91. Le 19mai 1992,le Gouvernement hongrois transmit au Gouverne-
ment tchécoslovaque une déclaration portant notification de la terminai-
son, par la Hongrie, du traité de 1977, à compter du 25 mai 1992. Dans
une lettre du mêmejour adresséeau premier ministre tchécoslovaque, le

premier ministre hongrois précisaitque la cause immédiatede la terminai-
son étaitle refus de la Tchécoslovaquie. exprimédans sa lettre du 23 avril
1992,de suspendre les travaux afférentsà la variante C pendant les efforts
de médiation de la Commission des Communautés européennes. Dans sa
déclaration, la Hongrie disait qu'elle ne pouvait accepter les effets néfastes
de la mise en Œuvre de la varianteC sur l'environnement et sur la protec-
tion de la nature, qui seraient pratiquement équivalentsaux dangers créés

par la réalisation du projet initial. Elle ajoutait que la varianteontre-
venait à de nombreux accords internationaux et violait l'intégritéterrito-
riale de la Hongrie en détournant le Danube de son cours naturel.

92. Au cours de la procédure, la Hongrie a présenté cinq motifsen vue
de démontrer que la notification de terminaison était licite, et par suite
effective: l'existence d'un état de nécessité,l'impossibilité d'exécuterle
traité, la survenance d'un changement fondamental de circonstances, la
violation substantielle du traité par la Tchécoslovaquie et, enfin, I'appari-
tion de nouvelles normes de droit international de l'environnement. La

Slovaquie a contesté chacun de ces motifs.
93. Sur le premier point, la Hongrie a affirméque, puisque la Tché-
coslovaquie ((était demeurée inflexible)) et avait poursuivi la mise en
Œuvre de la variante C, ((l'étatprovisoire de nécessité[était] finalement
devenu permanent, justifiant ainsi la terminaison du traité de 1977)).
Pour sa part, la Slovaquie, se fondant sur ce qu'elle estime êtreles don-59 GABCIKOVO-NAGYM PRR ECST(JUDGMENT)

basis of what it saw as the scientific facts; and argued that even if such a

state of necessity had existed, this would not give rise to a right to ter-
minate the Treaty under the Vienna Convention of 1969 on the Law of
Treaties.
94. Hungary's second argument relied on the terms of Article 61 of the
Vienna Convention, which is worded as follows:

"Article 61
Supervening Impossibility of'Pe~forrnunce

1. A party may invoke the impossibility of performing a treaty as
a ground for terminating or withdrawing from it if the impossibility
results from the permanent disappearance or destruction of an object

indispensable for the execution of the treaty. If the impossibility is
temporary, it may be invoked only as a ground for suspending the
operation of the treaty.
2. Impossibility of performance may not be invoked by a party as
a ground for terminating, withdrawing from or suspending the opera-

tion of a treaty if the impossibility is the result of a breach by that
party either of an obligation under the treaty or of any other inter-
national obligation owed to any other party to the treaty."

Hungary declared that it could not be "obliged to fulfil a practically
impossible task, namely to construct a barrage system on its own terri-
tory that would cause irreparable environmental damage". It concluded
that

"By May 1992 the essential object of the Treaty - an economic
joint investment which was consistent with environmental protection
and which was operated by the two parties jointly - had perma-

nently disappeared, and the Treaty had thus become impossible to
perform."
In Hungary's view, the "object indispensable for the execution of the

treaty", whose disappearance or destruction was required by Article 61 of
the Vienna Convention, did not have to be a physical object, but could
also include, in the words of the International Law Commission, "a legal
situation which was the raison d'êtreof the rights and obligations".

Slovakia claimed that Article 61 was the only basis for invoking impos-
sibility of performance as a ground for termination, that paragraph 1 of
that Article clearly contemplated physical "disappearance or destruction"
of the object in question, and that, in any event, paragraph 2 precluded
the invocation of impossibility "if the impossibility is the result of a

breach by that party . . . of an obligation under the treaty".

95. As to "fundamental change of circumstances", Hungary relied on
Article 62 of the Vienna Convention on the Law of Treaties which states

as follows:néesscientifiques, a contesté l'existence d'un état de nécessitéet a fait
valoir que, mêmesi un tel état de nécessitéavait existé, il n'aurait pu

conférer le droit de mettre fin au traité en vertu de la convention de
Vienne de 1969 sur le droit des traités.
94. Le deuxième argument de la Hongrie était tirédes termes de I'ar-
ticle 61 de la convention de Vienne, ainsi libellé:

Survrnunce d'une situution rendunt Iéxkcution impossible

1. Une partie peut invoquer l'impossibilité d'exécuterun traité
comme motif pour y mettre fin ou pour s'en retirer si cette impossi-
bilité résultede la disparition ou destruction définitivesd'un objet
indispensable à l'exécutionde ce traité. Si l'impossibilité esttempo-

raire, elle peut être invoquéeseulement comme motif pour suspendre
l'application du traité.
2. L'impossibilité d'exécution ne peut être invoquée par une partie
comme motif pour mettre fin au traité, pours'enretirer ou pour en sus-
pendre I'application si cette impossibilitérésulted'une violation, par la

partie qui l'invoque, soit d'une obligation du traité,soit de toute autre
obligation internationale à l'égardde toute autre partie au traité. ))

La Hongrie a déclaréqu'elle ne pouvait «êtreobligéed'accomplir une
tâche pratiquement impossible, à savoir construire un systèmede barrage
sur son propre territoire qui causerait des dommages irréparables à
l'environnement)). Elle a conclu que:

En mai 1992 l'objet essentiel du traité - un investissement éco-
nomique conjoint qui était compatible avec la protection de I'envi-
ronnement et qui étaitexploitépar les deux parties conjointement -
avait disparu de manière permanente, et [que] le traité était donc

devenu impossible à exécuter. ))
De l'avis de la Hongrie, il n'est pas nécessaire que la disparition ou la
destruction de l'«objet indispensable à l'exécutionde ce traité)),qu'exige

l'article 61 de la convention de Vienne, vise un objet physique; il peut
aussi s'agir, suivant les termes utiliséspar la Commission du droit inter-
national, d'«une situation juridique qui constituait la raison d'êtredes
droits et obligations)).
La Slovaquie a prétendu que la seule base sur laquelle l'impossibilité

d'exécutionpuisse t-tre invoquéecomme motif de terminaison d'un traité
est indiquéeà l'article 61 de la convention de Vienne; que le paragraphe 1
de cet article envisage manifestement la ((disparition ou destruction))
matériellede l'objet dont il s'agit; et que, en tout état de cause, selon le
paragraphe 2, on ne peut invoquer l'impossibilité d'exécution«si cette

impossibilité résulted'une violation, par la partie qui l'invoque, ... d'une
obligation aux termes du traité)).
95. En ce qui concerne le ((changement fondamental de circons-
tances)), la Hongrie se fonde sur l'article 62 de la convention de Vienne
sur le droit des traités, ainsi conçu: "Article 62
Fundumrntul Chunge of Circunzstances

1. A fundamental change of circumstances which has occurred
with regard to those existing at the time of the conclusion of a treaty,
and which was not foreseen by the parties, may not be invoked as a
ground for terminating or withdrawing from the treaty unless:

(a) the existence of those circumstances constituted an essential
basis of the consent of the parties to be bound by the treaty;
and
(h) the effect of the change is radically to transform the extent of

obligations still to be performed under the treaty.
2. A fundamental change of circumstances may not be invoked as
a ground for terminating or withdrawing from a treaty:

(a) if the treaty establishes a boundary; or
(h) if the fundamental change is the result of a breach by the party
invoking it either of an obligation under the treaty or of any
other international obligation owed to any other party to the
treaty.

3. If, under the foregoing paragraphs, a party may invoke a fun-
damental change of circumstances as a ground for terminating or
withdrawing from a treaty it may also invoke the change as a ground
for suspending the operation of the treaty."

Hungary identified a number of "substantive elements" present at the
conclusion of the 1977 Treaty which it said had changed fundamentally

by the date of notification of termination. These included the notion
of "socialist integration", for which the Treaty had originally been a
"vehicle", but which subsequently disappeared; the "single and indivisible
operational system", which was to be replaced by a unilateral scheme;
the fact that the basis of the planned joint investment had been over-
turned by the sudden emergence of both States into a market economy;

the attitude of Czechoslovakia which had turned the "framework treaty"
into an "immutable norm"; and, finally, the transformation of a treaty
consistent with environmental protection into "a prescription for envi-
ronmental disaster".

Slovakia, for its part, contended that the changes identified by Hun-
gary had not altered the nature of the obligations under the Treaty from
those originally undertaken, so that no entitlement to terminate it arose

from them.
96. Hungary further argued that termination of the Treaty was justi-
fied by Czechoslovakia's material breaches of the Treaty, and in this
regard it invoked Article 60 of the Vienna Convention on the Law of
Treaties, which provides: PROJET GABCIKOVO-NAGYM (ARROES)

«.4rticle62

Cllangement fondumental de circonstances
1. Un changement fondamental de circonstances qui s'est produit

par rapport à celles qui existaient au moment de la conclusion d'un
traité et qui n'avait pas étéprévu par les parties ne peut pas être
invoqué comme motif pour mettre fin au traité ou pour s'en retirer,
à moins que:

u) l'existence de ces circonstances n'ait constitué une base essen-
tielle du consentement des partiesà êtreliéespar le traité; et que

b) ce changement n'ait pour effet de transformer radicalement la
portée des obligations qui restent à exécuter en vertu du traité.

2. Un changement fondamental de circonstances ne peut pas être
invoqué comme motif pour mettre fin à un traitéou pour s'en retirer:

u) s'il s'agit d'un traité établissantune frontière; ou
h) si le changement fondamental résulted'une violation, par la par-
tie qui l'invoque, soit d'une obligation du traité, soit de toute

autre obligation internationalea l'égardde toute autre partie au
traité.
3. Si une partie peut, conformément aux paragraphes qui précè-

dent, invoquer un changement fondamental de circonstances comme
motif pour mettre fin à un traité ou pour s'en retirer, elle peut éga-
lement ne l'invoquer que pour suspendre l'application du traité. ))

La Hongrie a énumérédivers ((élémentsde fond» présents lors de la
conclusion du traité de 1977 qui, selon elle, avaient fondamentalement
changé à la date à laquelle elle a notifié qu'ellemettait fin au traité.
Parmi ces éléments,elle a évoquéla notion d'«intégration socialiste)),

dont le traité avait étéinitialement «le vecteur)), mais qui avait par la
suite disparu; le ((système d'ouvrages opérationnel, unique et indivi-
sible)), auquel avait été substitué un projet unilatéral;le fait que la base
de l'investissement conjoint prévu avait été radicalement transformée
avec l'entréesoudaine des deux Etats dans l'économiede marché; I'atti-

tude de la Tchécoslovaquie qui avait fait d'un «traité-cadre» une «norme
immuable)); et enfin, la transformation d'un traité qui tenait compte de
la protection de l'environnement en «traité porteur de catastrophes éco-
logiques ».
La Slovaquie, quant à elle, a soutenu que les changements signaléspar
la Hongrie n'avaient pas modifiéla nature des obligations prévues initia-

lement au traité,de sortequ'aucun droit d'y mettre fin ne pouvait décou-
ler de ces changements.
96. La Hongrie a en outre fait valoir que la terminaison du traitéétait
justifiéedu fait des violations substantielles de ce traité commises par la
Tchécoslovaquie, et elle a invoqué à cet égard l'article 60 de la conven-

tion de Vienne sur le droit des traités, qui dispose: GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

"Article 60
Terminution or Suspension of the Operution ofu Treaty
us u Consequence of ItsBreach

1.A material breach of a bilateral treaty by one of the parties
entitles the other to invoke the breach as a ground for terminating
the treaty or suspending its operation in whole or in part.

2. A material breach of a multilateral treaty by one of the parties

entitles:
(a) the other parties by unanimous agreement to suspend the opera-
tion of the treaty in whole or in part or to terminate it either:

(i) in the relations between themselves and the defaulting State,
or
(ii) as between al1the parties;

(b) a party specially affected by the breach to invoke it as a ground
for suspending the operation of the treaty in whole or in part in
the relations between itself and the defaulting State;

(c) any party other than the defaulting State to invoke the breach
as a ground for suspending the operation of the treaty in whole

or in part with respect to itself if the treaty is of such a charac-
ter that a material breach of its provisions by one party radi-
cally changes the position of every party with respect to the
further performance of its obligations under the treaty.

3. A niaterial breach of a treaty, for the purposes of this article,
consists in:
(a) a repudiation of the treaty not sanctioned by the present Con-
vention; or

(6) the violation of a provision essential to the accomplishment of
the object or purpose of the treaty.
4. The foregoing paragraphs are without prejudice to any provi-
sion in the treaty applicable in the event of a breach.

5. Paragraphs 1 to 3 do not apply to provisions relating to the
protection of the human person contained in treaties of a humani-
tarian character, in particular to provisions prohibiting any form of
reprisals against perçons protected by such treaties."

Hungary claimed in particular that Czechoslovakia violated the 1977
Treaty by proceeding to the construction and putting into operation of
Variant C, as well as failing to comply with its obligations under Ar-
ticles 15 and 19 of the Treaty. Hungary further maintained that Czecho-

slovakia had breached other international conventions (among them the
Convention of 31 May 1976 on the Regulation of Water Management
Issues of Boundary Waters) and general international law. PROJET GABCIKOVO-NAGYM(A ARRORÉT)

((Articlc 60
E'ctinction d'un truité ousu.spensionde son upplication
comme conséyuencede su violution

1. Une violation substantielle d'un traité bilatéral par I'une des
parties autorise l'autre partieà invoquer la violation comme motif
pour mettre fin au traitéou suspendre son application en totalité ou
en partie.

2. Une violation substantielle d'un traité multilatéralpar I'unedes
parties autorise:
U) lesautres parties, agissant par accord unanime, à suspendre I'appli-
cation du traitéen totalitéou en partie ou a mettre fin à celui-ci:

i) soit dans les relations entre elles-mêmeset 1'Etatauteur de la
violation,
ii) soit entre toutes les parties;

6) une partie spécialement atteinte par la violation à invoquer
celle-ci comme motif de suspension de l'application du traité
en totalitéou en partie dans les relations entre elle-mêmeet I'Etat
auteur de la violation;
c) toute partie autre que I'Etat auteur de la violation a invoquer la

violation comme motif pour suspendre l'application du traité en
totalité ou en partie en ce qui la concerne si ce traité est d'une
nature telle qu'une violation substantielle de ses dispositions par
une partie modifie radicalement la situation de chacune des parties
quant à l'exécution ultérieurede ses obligations en vertu du traité.

3. Aux fins du présent article, une violation substantielle d'un
traité est constituée par:
a) un rejet du traité non autorisé par la présente convention; ou

6) la violation d'une disposition essentielle pour la réalisation de
l'objet ou du but du traité.
4. Les paragraphes qui précèdent neportent atteinte a aucune dis-
position du traité applicable en cas de violation.

5. Les paragraphes 1 à 3 ne s'appliquent pas aux dispositions rela-
tives à la protection de la personne humaine contenues dans des
traités de caractère humanitaire, notamment aux dispositions
excluant toute forme de représailles à l'égard des personnes pro-
tégéespar lesdits traités.»

La Hongrie a prétendu en particulier que la Tchécoslovaquie avait violé
le traité de 1977 en procédant à la construction et à la mise en service
de la variante C, et en manquant a ses obligations au titre des articles 15
et 19 du traité. La Hongrie a par ailleurs soutenu que la Tchécoslova-

quie avait méconnu d'autres conventions internationales (dont la conven-
tion sur la réglementation en matière d'eaux frontières du 3 1 mai 1976)et
le droit international général.62 GABC~KOVO-NAGYM PAOROCT (JUDGMENT)

Slovakia denied that there had been, on the part of Czechoslovakia or
on its part, any material breach of the obligations to protect water qual-
ity and nature, and claimed that Variant C, far from being a breach, was
devised as "the best possible approximate application" of the Treaty. It

furthermore denied that Czechoslovakia had acted in breach of other
international conventions or general international law.

97. Finally, Hungary argued that subsequently imposed requirements
of international law in relation to the protection of the environment pre-

cluded performance of the Treaty. The previously existing obligation not
to cause substantive damage to the territory of another State had, Hun-
gary claimed, evolved into an ergu omnes obligation of prevention of
damage pursuant to the "precautionary principle". On this basis, Hun-
gary argued, its termination was "forced by the other party's refusal to
suspend work on Variant Cm.

Slovakia argued, in reply, that none of the intervening developments in
environmental law gave rise to norms of juscogens that would override
the Treaty. Further, it contended that the claim by Hungary to be
entitled to take action could not in any event serve as legal justification

for termination of the Treaty under the law of treaties, but belonged
rather "to the language of self-help or reprisals".

98. The question, as formulated in Article 2, paragraph 1 (c),of the
Special Agreement, deals with treaty law since the Court is asked to
determine what the legal effects are of the notification of termination of
the Treaty. The question is whether Hungary's notification of 19 May
1992 brought the 1977 Treaty to an end, or whether itdid not meet the

requirements of international law, with the consequence that it did not
terminate the Treaty.
99. The Court has referred earlier to the question of the applicability
to the present case of the Vienna Convention of 1969on the Law of Trea-
ties. The Vienna Convention is not directly applicable to the 1977Treaty

inasmuch as both States ratified that Convention only after the Treaty's
conclusion. Consequently only those rules which are declaratory of cus-
tomary law are applicable to the 1977 Treaty. As the Court has already
stated above (see paragraph 46), this is the case, in many respects, with
Articles 60 to 62 of the Vienna Convention. relatine "o termination or
suspension of the operation of a treaty. On this, the Parties, too, were

broadly in agreement.
100. The 1977Treaty does not contain any provision regarding its ter-
mination. Nor is there any indication that the parties intended to admit
the possibility of denunciation or withdrawal. On the contrary, the
Treaty establishes a long-standing and durable régimeof joint investment PROJET GABCIKOVO-NAGYM(A ARORET) 62

La Slovaquie a niéqu'il yait eu, de la part de la Tchécoslovaquie ou de
sa propre part, une violation substantielle des obligations de protéger la
qualitéde l'eau et la nature, et a affirméque la variante C, loin d'être une
violation du traité, constituait en fait «la meilleure application possible
[du traité]par approximation)). Elle a en outre niéque la Tchécoslova-

quie ait méconnu d'autres conventions internationales ou le droit inter-
national général.
97. La Hongrie a enfin soutenu que les normes du droit international
qui se sont imposéespar la suite en matière de protection de l'environ-
nement rendaient impossible l'exécutiondu traité. L'obligation qui exis-
tait préalablement de ne pas causer de dommage substantiel au territoire

d'un autre Etat était devenue avec le temps, au dire de la Hongrie, une
obligation ergu otnnes de prévention des dommages conformément au
((principe de précaution)). Sur cette base, la Hongrie a fait valoir qu'elle
avait étécontrainte de mettre fin au traité «en raison du refus de l'autre
partie de suspendre les travaux relatifa la variante CD.
La Slovaquie a exposé, en réponse, qu'aucun des nouveaux dévelop-
pements du droit international de l'environnement n'avait engendré de

normes de jus cogens qui prévaudraient sur le traité. Elle a soutenu en
outre que le droia agir dont la Hongrie entend se prévaloirn'aurait pu en
tout étatde cause justifier légalementla terminaison du traitéen vertu du
droit des traités, mais relevait bien davantage «du vocabulaire de I'auto-
protection ou des représailles)).

98. Telle qu'elle est formuléeà l'article 2, paragraphe 1, alinéac), du
compromis, la question poséerelèvedu droit des traités puisque la Cour
est ~riéede dire auels sont les effets iuridiaues de la notification de ter-
minaison du traité. Il s'agit de savoir si la notification hongroise du
19mai 1992a mis fin au traitéde 1977ou n'a Daseu cet effet. faute d'être

conforme aux exigences du droit international.

99. La Cour a déjàévoquéla question de l'applicabilitéà la présente
espèce de la convention de Vienne de 1969 sur le droit des traités. La
convention de Vienne n'est pas directement applicable au traité de 1977
dans la mesure où les deux Etats n'ont ratifiécette convention qu'après

avoir conclu le traité. En conséquence, seules les règlesde la convention
qui sont déclaratoires du droit coutumier sont applicables au traité de
1977.Comme la Cour l'a indiquéci-dessus (voirparagraphe 46), tel est le
cas, a bien des égards, des articles 60 à 62 de la convention de Vienne
relatifs à l'extinction atla suspension de l'application des traités. Les
Parties en ont aussi largement convenu.

100. Le traitéde 1977ne contient pas de disposition concernant sa ter-
minaison. Rien n'indique non plus que les parties entendaient admettre la
possibilitéde dénoncer le traité ou de s'en retirer. Au contraire, le traité
établit un système durable d'investissement conjoint et d'exploitation63 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

and joint operation. Consequently, the parties not having agreed other-
wise, the Treaty could be terminated only on the limited grounds enu-

merated in the Vienna Convention.

101. The Court will now turn to the first ground advanced by Hun-

gary, that of the state of necessity. In this respect, the Court will merely
observe that, even if a state of necessity is found to exist, it is not a
ground for the termination of a treaty. It may only be invoked to exon-
erate from its responsibility a State which has failed to implement a
treaty. Even if found justified, it does not terminate a Treaty; the Treaty

may be ineffective as long as the condition of necessity continues to exist;
it may in fact be dormant, but - unless the parties by mutual agreement
terminate the Treaty - it continues to exist. As soon as the state of
necessity ceases to exist, the duty to comply with treaty obligations

revives.

102. Hungary also relied on the principle of the impossibility of per-

formance as reflected in Article 61 of the Vienna Convention on the Law
of Treaties. Hungary's interpretation of the wording of Article 61 is,
however, not in conformity with the terms of that Article, nor with the
intentions of the Diplomatic Conference which adopted the Convention.

Article 6 1, paragraph 1, requires the "permanent disappearance or
destruction of an object indispensable for the execution" of the treaty to
justify the termination of a treaty on grounds of impossibility of perform-
ance. During the conference, a proposal was made to extend the scope of
the article by including in it cases such as the impossibility to make cer-

tain payments because of serious financial difficulties (Ojjciul Records of
the United Nations Conjerence on the Luiv qf' Treuties, First Session,
Vienna, 26 Murch-24 Muy 1968, doc. A/CONF.39/11, Summary records
of the plenary meetings and of the meetings of the Committee of the
Whole, 62nd Meeting of the Committee of the Whole, pp. 361-365).

Although it was recognized that such situations could lead to a preclu-
sion of the wrongfulness of non-performance by a party of its treaty
obligations, the participating States were not prepared to consider such
situations to be a ground for terminating or suspending a treaty,

and preferred to limit themselves to a narrower concept.
103. Hungary contended that the essential object of the Treaty - an
economic joint investment which was consistent with environmental pro-
tection and which was operated by the two contracting parties jointly -
had permanently disappeared and that the Treaty had thus become

impossible to perform. It is not necessary for the Court to determine
whether the term "object" in Article 61 can also be understood to
embrace a legal régime as in any event, even if that were the case, it PROJET GABCIKOVO-NAGYMAROS (ARRET) 63

conjointe. Par conséquent, les parties n'en ayant pas convenu autrement,
le traité ne pouvait prendre fin que pour les motifs énuméréslimitative-
ment dans la convention de Vienne.

101. La Cour examinera maintenant le premier motif invoqué par la
Hongrie, a savoir celui tiréde l'étatde nécessité.A cet égard,la Cour se
bornera a observer que mêmesi l'existence d'un étatde nécessitéest éta-

blie,ilne peut êtremis fin a un traité sur cette base. L'état de nécessiténe
peut êtreinvoquéque pour exonérerde sa responsabilité un Etat qui n'a
pas exécutéun traité. Mêmesi l'on considère que l'invocation de ce motif
est justifiée,le traiténe prend pas fin pour autant; il peut êtreprivé d'effet
tant que l'étatde nécessitépersiste; il peut êtreinopérant en fait, mais il
reste en vigueur, a moins que les parties n'y mettent fin d'un commun

accord. Dès que l'étatde nécessitédisparaît, le devoir de s'acquitter des
obligations découlant du traité renaît.

102. La Hongrie invoque aussi le principe de l'impossibilité d'exécu-

tion tel que traduit à I'article 61 de la convention de Vienne sur le droit
des traités. Toutefois elle semble interpréter cette disposition d'une façon
qui n'est conforme ni à son libellé niaux intentions expriméeslors de la
conférencediplomatique qui a adopté la convention. Le paragraphe 1 de
l'article 61 exige qu'il y ait eu ((disparition ou destruction définitivesd'un
objet indispensable à l'exécution» d'un traité, pour que l'impossibilité

d'exécution puissejustifier la terniinaison dudit traité. Au cours de la
conférence, il a étéproposé d'élargir la portée de cet article jusqu'à
inclure des cas tels que I'impossjbilitéd'effectuer certains paiements en
raison de difficultésfinancières graves (Doc~rnent~soJ$cicls dc2lu confZ-
r-cncedes "VutiorisUnies sur.le droir des truitGs,pr.c~rni6r.ession, Vienne,

26 niurs-24 filui 1968, doc. A/CONF.39/11, comptes rendus analytiques
des séances plénières et des séancesde la commission plénière,62' séance
de la commission plénière, p.393-397). Bien qu'il ait étéadmis que de
telles situationspourraient exclure I'illicéitde l'inexécution,par une par-
tie, de ses obligations conventionrielles, les Etats participants n'ont pas
étédisposésà en faire un motif d'extinction ou de suspension d'un traité

et ont préféré s'en tenir à une conception plus étroite.

103. La Hongrie a soutenu que l'objet essentiel du traité - un inves-
tissement économique conjoint compatible avec la protection de I'envi-
ronnement et exploité conjointement par les deux parties contractantes
- avait définitivement disparu, et que l'exécution du traité étaitainsi

devenue impossible. La Cour n'a pas a déterminer si le mot «objet» figu-
rant à I'article 61 peut aussi êtreinterprétécomme visant un régimejuri-
dique car en tout état de cause, mêmesi tel était le cas, elle aurait awould have to conclude that in this instance that régimehad not defini-
tively ceased to exist. The 1977Treaty - and in particular its Articles 15,
19 and 20 - actually made available to the parties the necessary means
to proceed at any time, by negotiation, to the required readjustments

between economic imperatives and ecological imperatives. The Court
would add that, if the joint exploitation of the investment was no longer
possible, this was originally because Hungary did not carry out most of
the works for which it was responsible under the 1977Treaty; Article 61,
paragraph 2, of the Vienna Convention expressly provides that impossi-
bility of performance may not be invoked for the termination of a treaty

by a party to that treaty when it results from that party's own breach of
an obligation flowing from that treaty.

104. Hungary further argued that it was entitled to invoke a number
of events which, cumulatively, would have constituted a fundamental
change of circumstances. In this respect it specified profound changes of

a political nature, the Project's diminishing economic viability, the
progress of environmental knowledge and the development of new norms
and prescriptions of international environmental law (see paragraph 95
above).

The Court recalls that, in the Fislzrries Jurisdiction case, it stated that

"Article 62 of the Vienna Convention on the Law of Treaties, . ..
may in many respects be considered as a codification of existing cus-
tomary law on the subject of the termination of a treaty relationship
on account of change of circumstances" (I.C.J. Reports 1973, p. 63,
para. 36).

The prevailing political situation was certainly relevant for the conclu-

sion of the 1977Treaty. But the Court will recall that the Treaty provided
for a joint investment programme for the production of energy, the con-
trol of floods and the improvement of navigation on the Danube. In the
Court's view, the prevalent political conditions were thus not so closely
linked to the object and purpose of the Treaty that they constituted an
essential basis of the consent of the parties and, in changing, radically

altered the extent of the obligations still to be performed. The same holds
good for the economic system in force at the time of the conclusion of the
1977 Treaty. Besides, even though the estimated profitability of the
Project might have appeared less in 1992than in 1977, it does not appear
from the record before the Court that it was bound to diminish to such
an extent that the treaty obligations of the parties would have been radi-
cally transformed as a result.

The Court does not consider that new developments in the state of PROJET GABCIKOVO-NAGYM(A ARRRSÈT) 64

conclure qu'en l'espècece régimen'avait pas définitivement disparu. Le
traité de 1977 - et en particulier ses articles 15, 19 et -0 offrait en
effet aux parties les moyens nécessaires pour procéder a tout moment,
par voie de négociation, aux réajustements requis entre impératifs écono-
miques et impératifs écologiques. L.aCour ajoutera que, si l'exploitation

conjointe de l'investissement n'a plus étépossible, c'eiil'origine, parce
que la Hongrie n'a pas exécutéla plupart des travaux qui lui incombaient
aux termes du traité de 1977; or le paragraphe 2 de l'article 61 dela
convention de Vienne prévoit expressément que l'impossibilité d'exécu-
tion ne peut êtreinvoquéepour la terminaison d'un traité par une partie
a ce traité lorsque cette impossibilité résultede la violation par la même

partie d'une obligation découlant dudit traité.

104. La Hongrie soutient en outre qu'elle était en droit d'invoquer
diversévénements qui,en se cumulant, auraient constitué un changement
fondamental de circonstances. A cet effet, elle a plus particulièrement
mentionné des changements profonds de nature politique, le fait que le
projet devenait de moins en moins rentable, les progrès des connaissances

en matière d'environnement et le développement de nouvelles normes et
prescriptions du droit international de l'environnement (voir para-
graphe 95 ci-dessus).
La Cour rappellera que, dans l'affaire de la Compétenceen mutière de
pr^cherie.s,elle a dit que

((l'article 62 de la convention de Vienne sur le droit des traités ...
peut, a bien des égards, êtreconsidérécomme une codification du

droit coutumier existant en ce qui concerne la cessation des relations
converitionnelles en raison d'un changement de circonstances»
(C.I.J. Recueil 1973, p. 63, par. 36).

Certes, la situation politique qui prévalait alors a certainement étéper-
tinente au regard de la conclusion du traitéde 1977. Mais la Cour rappel-
lera que ce traitéprévoyait un programme d'investissement conjoint pour
la production d'énergie,la maîtrise des inondations et l'amélioration des
conditions de navigation sur le Danube. De l'avis de la Cour, les condi-

tions politiques de l'époque n'étaient onc pas liées l'objet et au but du
traité au point de constituer une base essentielle du consentement des
parties et, en se modifiant, de transformer radicalement la portéedes obli-
gations qui restaientiexécuter. Ilen va de mêmedu systèmeéconomique
en vigueur au moment de la conclusion du traité de 1977. Par ailleurs,
mêmesi la rentabilité estiméedu projet pouvait apparaître moins élevéeen
1992qu'en 1977,il ne ressort pas du dossier soumisa la Cour qu'elle était

condamnée i chuter dans une proportion telle que les obligations conven-
tionnelles des parties s'en fussent trouvées radicalement transformées.
La Cour ne saurait considérerque les nouvelles connaissances acquisesenvironmental knowledge and of environmental law can be said to
have been completely unforeseen. What is more, the formulation of
Articles 15, 19 and 20, designed to accommodate change, made it pos-
sible for the parties to take account of such developments and to apply

them when implementing those treaty provisions.
The changed circumstances advanced by Hungary are, in the Court's
view, not of such a nature, either individually or collectively, that their
effect would radically transform the extent of the obligations still to be
performed in order to accomplish the Project. A fundamental change of
circumstances must have been unforeseen; the existence of the circum-

stances at the time of the Treaty's conclusion must have constituted an
essential basis of the consent of the parties to be bound by the Treaty.
The negative and conditional wording of Article 62 of the Vienna Con-
vention on the Law of Treaties is a clear indication moreover that the
stability of treaty relations requires that the plea of fundamental change
of circumstances be applied only in exceptional cases.

105. The Court will now examine Hungary's argument that it was
entitled to terminate the 1977Treaty on the ground that Czechoslovakia

had violated its Articles 15, 19and 20 (as well as a number of other con-
ventions and rules of general international law); and that the planning,
construction and putting into operatinn of Variant C also amounted to a
material breach of the 1977 Treatv.
106. As to that part of Hungary's argument which was based on other
treaties and general rules of international law, the Court is of the view

that it is only a material breach of the treaty itself, by a State party to
that treaty, which entitles the other party to rely on it as a ground for
terminating the treaty. The violation of other treaty rules or of rules of
general international law may justify the taking of certain measures,
including countermeasures, by the injured State, but it does not consti-
tute a ground for termination under the law of treaties.

107. Hungary contended that Czechoslovakia had violated Articles 15,
19 and 20 of the Treaty by refusing to enter into negotiations with Hun-
gary in order to adapt the Joint Contractual Plan to new scientific and
legal developments regarding the environment. Articles 15, 19 and 20
oblige the parties jointly to take, on a continuous basis, appropriate

measures necessary for the protection of water quality, of nature and of
fishing interests.

Articles 15 and 19 expressly provide that the obligations they contain
shall be implemented by the means specified in the Joint Contractual
Plan. The failure of the parties to agree on those means cannot, on the

basis of the record before the Court, be attributed solely to one party. PROJET GABCIKOVO-NAGYMAROS (ARRET) 65

en matière d'environnement et les progrès du droit de l'environnement
aient présenté un caractère complètement imprévu.Bien plus, le libellé
des articles 15, 19et 20, conçu dans une perspective d'évolution, a mis les
parties en mesure de tenir compte de ces développements et de les appli-

quer lorsqu'elles exécuteraient ces dispositions conventionnelles.
De l'avis de la Cour, les changements de circonstances que la Hongrie
invoque ne sont pas, pris séparémentou conjointement, d'une nature telle
qu'ils aient pour effet de transfornier radicalement la portée des obliga-
tions qui restent à exécuter pour réaliserle projet. Un changement fon-

damental de circonstances doit être imprévu; les circonstances existant à
l'époqueoù le traité a été conclu doiventavoir constitué une base essen-
tielle du consentement des parties à êtreliéespar le traité. Le fait que
l'article 62 de la convention de Vienne sur le droit des traités soit libellé
en termes négatifs et conditionnels indique d'ailleurs clairement que la
stabilitédes relations conventionnelles exige que le moyen tiréd'un chan-

gement fondamental de circonstances ne trouve iis'appliquer que dans
des cas exceptionnels.

105. La Cour examinera maintenant l'argument de la Hongrie selon
lequel cet Etat était en droit de mettre fin au traité de 1977 au motif que
la Tchécoslovaquie en avait violéles articles 15. 19et 20 (ainsi que plu-
sieurs autres conventions et règlesdu droit international général),et que
la danification. la construction et la mise en service de la variante C

constituaient aussi une violation substantielle du traité de 1977.
106. Pour ce qui est de la branche de l'argumentation de la Hongrie
concernant d'autres conventions et règles généralesdu droit internatio-
nal, la Cour estime que seule une violation substantielle du traité lui-
mêmepar un Etat prtie audit traité peut mettre l'autre partie en droit de
s'en prévaloir pour mettre fin aii traité. La violation d'autres règles

conventionnelles ou d'autres règles du droit international général peut
justifier l'adoption par 1'Etat léséde certaines mesures, y compris des
contre-mesures, mais elle ne saurait justifier qu'il soit mis fin au traitésur
la base du droit des traités.
107. La Hongrie a soutenu que la Tchécoslovaquie avait violéles ar-

ticles 15, 19et 20 du traité en refusant d'engager avec elle des négocia-
tions en vue d'adapter le plan contractuel conjoint pour tenir compte des
nouveaux progrès scientifiques etjuridiques en matière d'environnement.
Les articles 15, 19 et 20 mettent <ila charge des parties l'obligation de
prendre conjointement et de façon continue des mesures appropriées
pour assurer la protection de la qualitédes eaux, de la nature et des inté-

rêtsen matière de pêcheries.
Les articles 15 et 19 prévoient expressément que les obligations qu'ils
contiennent seront mises en Œuvre selon les modalités prévues au plan
contractuel conjoint. Que les parties n'aient pu se mettre d'accord sur ces
modalités ne saurait, sur la base du dossier soumis à la Cour, être66 GABC~KOVO-NAGYM PAOROCT (JUDGMENT)

The Court has not found sufficient evidence toconclude that Czechoslo-
vakia had consistently refused to consult with Hungary about the desir-
ability or necessity of measures for the preservation of the environment.
The record rather shows that, while both parties indicated, in principle, a
willingness to undertake further studies, in practice Czechoslovakia
refused to countenance a suspension of the works at Dunakiliti and,

later, on VariantC, while Hungary required suspension as a prior condi-
tion of environmental investigation because it claimed continuation of
the work would prejudice the outcome of negotiations. In this regard it
cannot be left out of consideration that Hungaryitself, by suspending the
works at Nagymaros and Dunakiliti, contributed to the creation of a
situation which was not conducive to the conduct of fruitful negotiations.

108. Hungary's main argument for invoking a material breach of the
Treaty was the construction and putting into operation of Variant C. As

the Court has found in paragraph 79 above, Czechoslovakia violated the
Treaty only when it diverted the waters of the Danube into the bypass
canal in October 1992. In constructing the works which would lead to
the putting into operation of Variant C, Czechoslovakia did not act
unlawfully.
In the Court's view, therefore, the notification of termination by Hun-

gary on 19 May 1992 was premature. No breach of the Treaty by
Czechoslovakia had yet taken place and consequently Hungary was not
entitled to invoke any such breach of the Treaty as a ground for termi-
nating it when it did.
-109. In this regard, it should be noted that, according to Hungary's
Declaration of 19 May 1992, the termination of the 1977 Treaty was to

take effect as from 25 May 1992, that is only six days later. Both Parties
agree that Articles65 to 67 of the Vienna Convention on the Law of
Treaties, if not codifying customary law, at least generally reflect custom-
ary international law and contain certain procedural principles which are
based on an obligation to act in good faith. As the Court stated in its
Advisory Opinion on the Interpretufion of tlze Agreement of 25 March

1951 hetiilren tlze WHO und Egypt (in which case the Vienna Convention
did not apply) :

"Precisely what periods of time may be involved in the observance
of the duties to consult and negotiate, and what period of notice of
termination should be given, are matters which necessarily Vary
according to the requirements of the particular case. In principle,
therefore, it is for the parties in each case to determine the length of

those periods by consultation and negotiation in good faith." C.J.
Reports 1980, p. 96, para. 49.)
The termination of the Treaty by Hungary was to take effect six days PROJET GABCIKOVO-NAGYM(A ARRORET) 66

attribué uniquement à une seule des parties. De l'avis de la Cour, il
n'existe pas d'élémentsde preuve suffisants pour conclure que la Tché-
coslovaquie aurait constamment refuséde se concerter avec la Hongrie
sur l'opportunité ou la nécessitéde prendre des mesures de protection de
l'environnement. Ce que le dossier fait apparaître, c'est qu'alors que les
deux parties se montraient en principe disposéesà entreprendre de nou-

velles études,en pratique, la Tchécoslovaquie refusait d'envisager que les
travaux iiDunakiliti et, plus tard, ceux relatifs à la variante C soient sus-
pendus, cependant que la Hongrie demandait leur suspension comme
condition préalable à des recherches sur l'environnement, en expliquant
que la poursuite des travaux compromettrait l'issue des négociations. A

cet égard, la Cour ne saurait perdre de vue que la Hongrie elle-même,en
suspendant les travaux à Nagymaros et Dunakiliti, a contribué à la sur-
venance d'une situation aui ne uouvait êtrefavorable a la conduite de
négociations fructueuses.
108. L'argument principal de la Hongrie lorsqu'elle invoque une viola-
tion substantielle du traité est la construction et la mise en service de la

variante C. Comme la Cour l'a dit au paragraphe 79 ci-dessus, la Tché-
coslovaquie n'a violé le traité que lorsqu'elle a détourné les eaux du
Danube dans le canal de dérivation en octobre 1992. En construisant les
ouvrages qui devaient conduire à la mise en service de la variante C, la
Tchécoslovaquie n'a pas agi de façon illicite.
En conséquence, la Cour est d'avis que la notification par la Hongrie,

le 19 mai 1992, de la terminaison du traité était prématurée.Il n'y avait
pas encore eu de violation du traité par la Tchécoslovaquie; la Hongrie
n'étaitdonc pas en droit d'invoquer semblable violation du traité comme
motif pour y mettre fin au moment où elle l'a fait.
109. A cet égard,il y a lieu de relever que, d'après la déclaration que la
Hongrie a faite le 19 mai 1992, la terminaison du traité de 1977 devait

prendre effet à compter du 25 mai 1992, soit six jours plus tard seule-
ment. Les deux Parties s'accordent à reconnaître que les articles 65 à 67
de la convention de Vienne sur le droit des traités, s'ils ne codifient pas le
droit coutumier, le reflètent du moins généralementet contiennent cer-
tains principes de procédure qui ont pour fondement l'obligation d'agir

de bonne foi. Ainsi que la Cour l'a dit dans l'avis consultatif qu'elle a
donné sur l'lnterprétution de luccord du 25 murs 1951 entre l'OMS et
I'Egyptr (affaire dans laquelle la convention de Vienne ne s'appliquait
pas) :

«Les délaisprécisqui peuvent êtrenécessairespour s'acquitter des
obligations de consultation et de négociation et le préavisde dénon-
ciation exact qui doit êtredonné varient forcément en fonction des
nécessitésde l'espèce.En principe, c'est donc aux parties qu'il appar-
tient de déterminer dans chaque cas la duréede ces délais en procé-

dant de bonne foi à des consultations et à des négociations.)) (CJ..
Recueil 1980, p. 96, par. 49.)

La terminaison du traité par la Hongrie devait prendre effet six jours67 GABCIKOVO-NAGYM PRORECT (JUDGMENT)

after its notification. On neither of these dates had Hungary suffered

injury resulting from acts of Czechoslovakia. The Court must therefore
confirm its conclusion that Hungary's termination of the Treaty was
premature.
110. Nor can the Court overlook that Czechoslovakia committed the
internationally wrongful act of putting into operation Variant C as a
result of Hungary's own prior wrongful conduct. As was stated by the

Permanent Court of International Justice:

"It is, moreover, a principle generally accepted in the jurispru-
dence of international arbitration,as well as by municipal courts,
that one Party cannot avail himself of the fact that the other has not
fulfilled some obligation or has not had recourse to some means of
redress, if the former Party has, by some illegal act, prevented the

latter from fulfilling the obligation in question, or from having
recourse to the tribunal which would have been open to him." (Fuc-
tory at Chorzo~v, Jurisdiction, Juclgment No. 8, 1927, P.C.IJ..
Series A, No. 9, p.31.)

Hungary, by its own conduct, had prejudiced its right to terminate the
Treaty; this would still have been the case even if Czechoslovakia, by the
time of the purported termination, had violated a provision essential to

the accomplishment of the object or purpose of the Treaty.

111. Finally,the Court will address Hungary's claim that it was
entitled to terminate the 1977 Treaty because new requirements of inter-
national law for the protection of the environment precluded perfor-

mance of the Treaty.
112. Neither of the Parties contended that new DeremDtorv norms of
environmental law had emerged since the conclusion of tke 1677Treaty,
and the Court will consequently not be required to examine the scope of
Article64 of the Vienna Convention on the Law of Treaties. On the other
hand, the Court wishes to point out that newly developed norms of envi-

ronmental law are relevant for the implementation of the Treaty and that
the parties could, by agreement, incorporate them through the applica-
tion of Articles 15, 19and 20 of the Treaty. These articles do not contain
specific obligations of performance but require the parties, in carrying
out their obligations to ensure that the quality of water in the Danube is
not impaired and that nature is protected, to take new environmental

norms into consideration when agreeing upon the means to be specified
in the Joint Contractual Plan.

By inserting these evolving provisions in the Treaty, the parties recog-
nized the potential necessity to adapt the Project. Consequently, the PROJET GABC~KOVO-NAGYM (ARRROST) 67

après sa notification. Or,a aucune de ces deux dates, la Hongrie n'avait
subi de préjudicedu fait d'actes de la Tchécoslovaquie. La Cour est donc
amenéeà confirmer sa conclusion selon laquelle la terminaison du traité
par la Hongrie était prématurée.
110. La Cour ne saurait pas non plus perdre de vue que la Tchécoslo-
vaquie a commis l'acte internationalement illicite consistant à mettre en
service la variante C, à la suite du comportement illicite préalable de la

Hongrie elle-même.Comme l'a dit la Cour permanente de Justice inter-
nationale:

«C'est, du reste, un principe généralement reconnupar la jurispru-
dence arbitrale internationale, aussi bien que par les juridictions
nationales, qu'une Partie ne saurait opposer à l'autre le fait de ne pas
avoir rempli une obligation ou de ne pas s'êtreservi d'un moyen de
recours, si la première, par un acte contraire au droit, a empêché la
seconde de remplir l'obligation en question, ou d'avoir recours à la

juridiction qui lui aurait étéouverte.))(Usine de Cl~or.:oiv,compé-
tencc, urrêtno 8, 1927, C.P.J.I. sérieA no 9, p. 31.)

La Hongrie, par son comportement, avait porté atteinte à son droit de
mettre fin au traité; il en serait demeuréainsi mêmesi la Tchécoslovaquie
avait, au moment de la prétendue terminaison du traité, violéune dispo-
sition essentielle pour la réalisation1de l'objet ou du but du traité.

111. La Cour examinera enfin la prétentionde la Hongrie selon laquelle
cette dernière était en droit de mettre fin au traité1977, parce que les
nouvelles exigences du droit international relatafla protection de l'envi-
ronnement s'opposaient à l'exécutiondu traité.
112. Aucune des Parties n'a prétendu que des normes impératives du

droit de l'environnement soient néesdepuis la conclusion du traité de
1977 et la Cour n'aura par suite pas à s'interroger sur la portée de l'ar-
ticle 64 de la convention de Vienne sur le droit des traités. En revanche, la
Cour tient à relever que de nouvelles normes du droit de l'environne-
ment, récemmentapparues, sont pertinentes pour l'exécutiondu traitéet
que les parties pouvaient, d'un commun accord, en tenir compte en appli-

quant les articles 15,19 et 20 du traité. Ces articles ne contiennent pas
d'obligations spécifiques de faire., mais ils imposent aux parties, en
s'acquittant de leurs obligations de veiller à ce que la qualitédes eaux du
Danube ne soit pas compromise et à ce que la protection de la nature soit
assurée, de tenir compte des nouvelles normes en matière d'environne-
ment lorsque ces parties conviennent des moyens à préciserdans le plan
contractuel conjoint.

En insérant dans le traité ces dispositions évolutives, les parties ont
reconnu la nécessitéd'adapter éventuellement le projet. En conséquence,68 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

Treaty is not static, and is open to adapt to emerging norms of interna-
tional law. By means of Articles 15and 19,new environmental norms can

be incorporated in the Joint Contractual Plan.

The responsibility to do this was a joint responsibility. The obligations
contained in Articles 15, 19and 20 are, by definition, general and have to
be transformed into specific obligations of performance through a pro-
cess of consultation and negotiation. Their implementation thus requires

a mutual willingness to discuss in good faith actual and potential environ-
mental risks.
It isl1the more important to do this because as the Court recalled in
its Advisory Opinion on the Legulity of the Threut or Use of Nucleur
Weupons, "the environment is not an abstraction but represents the living
space, the quality of life and the very health of human beings, including

generations unborn" (I. C.J. Reports 1996, p. 241, para. 29; see also para-
graph 53 above).
The awareness of the vulnerability of the environment and the recogni-
tion that environmental risks haveto be assessed on a continuous basis
have become much stronger in the years since the Treaty's conclusion.
These new concerns have enhanced the relevance of Articles 15, 19
and 20.

113. The Court recognizes that both Parties agree on the need to take
environmental concerns seriously and to take the required precautionary
measures, but they fundamentally disagree on the consequences this has
for the joint Project. In such a case, third-party involvement may be help-
ful and instrumental in finding a solution, provided each of the Parties is
flexible in its position.

114. Finally, Hungary maintained that by their conduct both parties
had repudiated the Treaty and that a bilateral treaty repudiated by both
parties cannot survive. The Court is of the view, however, that although
it has found that both Hungary and Czechoslovakia failed to comply
with their obligations under the 1977 Treaty, this reciprocal wrongful

conduct did not bring the Treaty to an end nor justify its termination.
The Court would set a precedent with disturbing implications for treaty
relations and the integrity of the rule puctu sunt servunda if it were to
conclude that a treaty in force between States, which the parties have
implemented in considerable measure and at great cost over a period of
years, might be unilaterally set aside on grounds of reciprocal non-

compliance. It would be otherwise, of course, if the parties decided to
terminate the Treaty by mutual consent. But in this case, while Hungary
purported to terminate the Treaty, Czechoslovakia consistently resisted
this act and declared it to be without legal effect. PROJET GABC~KOVO-NAGYM (ARRROST) 68

le traité n'est pas un instrument figé et estsusceptible de s'adapter à de
nouvelles normes du droit international. Au moyen des articles 15 et 19,
de nouvelles normes en matière d'environnement peuvent être incorpo-
réesdans le plan contractuel conjoint.
La responsabilité d'agir de la sorte était une responsabilité conjointe.
Les obligations énoncéesaux articles 15, 19 et 20 sont, par définition,

d'ordre général,et doivent êtretransformées en obligations spécifiquesde
faire, à l'issue d'un processus de consultation et de négociation. De ce fait
leur mise en Œuvre exige une disposition réciproque à discuter de bonne
foi des risques réels etpotentiels pour I'environnement.
Agir de la sorte est d'autant plus important que la Cour, dans son avis

consultatif sur la Licéitéde lamenuce ou d~ l'en?ploid'urrnesnucléuires,
a rappelé que ((l'environnement n'est pas une abstraction, mais bien
l'espace ou vivent les êtreshumains et dont dépendent la qualité de leur
vie et leur santé,y compris pour les générationsà venir)) (C.I.J. Recueil
1996, p. 241, par. 29; voir aussi le paragraphe 53 ci-dessus).
La conscience que I'environnement est vulnérable et la reconnaissance

de ce qu'il faut continuellement évaluer les risques écologiques se sont
affirméesde plus en plus dans les annéesqui ont suivi la conclusion du
traité. Ces nouvelles préoccupations ont rendu les articles 15, 19et20 du
traité d'autant plus pertinents.
113. La Cour reconnaît que les Parties s'accordent sur la nécessitéde
se soucier sérieusement de I'environnement et de prendre les mesures de

précaution qui s'imposent, mais elles sont fondamentalement en désac-
cord sur les conséquences qui en découlent pour le projet conjoint. Dans
ces conditions, le recours à une tierce partie pourrait se révéler utile et
permettre de trouver une solution, à condition que chacune des Parties
fasse preuve de souplesse dans ses positions.
114. Enfin, la Hongrie a soutenu que par leur comportement les deux

parties avaient rejetéle traité et qu'un traité bilatéral ne saurait survivre
à son rejet par les deux parties. Bien qu'elle ait constaté que tant la Hon-
grie que la Tchécoslovaquie avaient manquéà leurs obligations découlant
du traité de 1977, la Cour estime que ces comportements illicites récipro-
ques n'ont pas mis fin au traité ni justifié qu'il y fût mis fin. La Cour
établirait un précédentaux effets perturbateurs pour les relations conven-

tionnelles et l'intégritéde la règle pucfrr sunt servundu si elle devait
conclure qu'il peut être unilatéralement mis fin, au motif de manque-
ments réciproques, ;iun traité en vigueur entre Etats, que les parties Ont
exécutédans une très large mesure et à un coût considérable pendant
des années.Il en serait à l'évidenceautrement si les parties décidaient de

mettre fin au traitéd'un commun accord. Mais, en l'espèce,si la Hongrie
a prétendu mettre fin au traité, la Tchécoslovaquie s'est constamment
opposéeà cette terminaison, déclarant qu'un tel acte serait dénuéde tout
effet juridique. 115. In the light of the conclusions it has reached above, the Court, in
reply to the question put to it in Article 2, paragraph 1 (c), of the Special

Agreement (see paragraph 89), finds that the notification of termination
by Hungary of 19 May 1992 did not have the legal effect of terminating
the 1977 Treaty and related instruments.

116. In Article 2,paragraph 2, of the Special Agreement, the Court is

requested to determine the legal consequences, including the rights and
obligations for the Parties, arising from its Judgment on the questions
formulated in paragraph 1. In Article 5 of the Special Agreement the
Parties agreed to enter into negotiations on the modalities for the execu-
tion of the Judgment immediately after the Court has rendered it.
117. The Court must first turn to the question whether Slovakia

became a party to the 1977Treaty as successoi to Czechoslovakia. As an
alternative argument, Hungary contended that, even if the Treaty sur-
vived the notification of termination, in any event it ceased to be in force
as a treaty on 31 December 1992,as a result of the "disappearance of one
of the parties". On that date Czechoslovakia ceased to exist as a legal
entity, and on 1 January 1993the Czech Republic and the Slovak Repub-

lic came into existence.

118. According to Hungary, "There is no rule of international law
which provides for automatic succession to bilateral treaties on the dis-
appearance of a party" and such a treaty will not survive unless another
State succeeds to it by express agreement between that State and the

remaining party. While the second paragraph of the Preamble to the
Special Agreement recites that

"the Slovak Republic is one of the two successor States of the Czech
and Slovak Federal Republic and the sole successor State in respect
of rights and obligations relating to the Gabtikovo-Nagymaros
Project",

Hungary sought to distinguish between, on the one hand, rights and obli-
gations such as "continuing property rights" under the 1977Treaty, and,
on the other hand, the treaty itself. It argued that, during the negotiations
leading to signature of the Special Agreement, Slovakia had proposed a

text in which it would have been expressly recognized "as the successor to
the Government of the CSFR" with regard to the 1977 Treaty, but that
Hungary had rejected that formulation. It contended that it had never
agreed to accept Slovakia as successor to the 1977 Treaty. Hungary
referred to diplomatic exchanges in which the two Parties had each sub-
mitted to the other lists of those bilateral treaties which they respectively

wished should continue in force between them. for negotiation on a case- PROJET GAB~IKOVO-NAGYMAROS (ARRET) 69

115. Au vu des conclusions auxquelles elle est parvenue ci-dessus,

la Cour répond à la question qui lui a étéposée à l'article 2, para-
graphe 1, alinéa c),du compromis (voir paragraphe 89) que la notifica-
tion de terminaison faite par la Hongrie le 19 mai 1992 n'a pas eu pour
effet juridique de mettre fin au traité de 1977 et aux instruments y affé-
rents.

116. Au paragraphe 2 de l'article 2 du compromis, la Cour a étépriée
de déterminer les conséquencesjuridiques, y compris les droits et obliga-
tions pour les Parties, de l'arrêt qu'ellerendra sur les questions énoncées
au paragraphe 1. A l'article5 du compromis, les Parties sont convenues
d'engager des négociations sur les modalités d'exécution de l'arrêt,dès
que la Cour l'aura rendu.

117. La Cour doit tout d'abord examiner la question de savoir si la
Slovaquie est devenue partie au traité de 1977en tant qu'Etat successeur
de la Tchécoslovaquie. A titre d'argument subsidiaire, la Hongrie a en
effet soutenu que, mêmes'il avait survécuà la notification de terminai-
son, le traité aurait en tout état de cause cesséd'êtreen vigueur en tant
que traité le 31 décembre 1992, a la suite de la ((disparition de l'une des
parties)). A cette date, la Tchécoslovaquie a cesséd'exister comme entité

juridique et, le1" janvier 1993, la République tchèque et la République
slovaque ont vu le jour.
118. De l'avis de la Hongrie: ((Aucune règlede droit international ne
prévoit la succession automatique à un traité bilatéral après disparition
de l'une des parties)); un tel traiténe saurait survivre que si un autre Etat
y succède par accord exprès entre ledit Etat et la partie qui s'est mainte-

nue. Or, bien qu'il soit affirméau deuxième paragraphe du préambule du
compromis que

«la République slovaque est l'un des deux Etats successeurs de la
République fédérative tchèque et slovaque et l'unique Etat succes-
seur en ce qui concerne les droits et obligations relatifs au projet
Gabkikovo-Nagymaros »,

la Hongrie a entendu distinguer entre,d'une part, les droits et obligations
établispar le traitéde 1977qui, tels«les droits de propriété...perdurent))
et, d'autre part, le traité lui-même.Elle a soutenu qu'au cours des négo-

ciations qui ont abouti à la signature du compromis la Slovaquie avait
proposé un texte dans lequel elle aurait étéexpressémentreconnue comme
((Etat successeur de la République fédérative tchèque etslovaque)) au
regard du traité de 1977, mais que la Hongrie avait rejeté un tel libellé.
Elle a fait observer qu'elle n'avait jamais accepté la Slovaquie comme
successeur au traité de 1977. La Hongrie s'est référée à des échanges
diplomatiques dans lesquels les deux Parties s'étaientmutuellement sou-

mis, en vue d'une négociation au cas par cas, les listes des traités bilaté-70 GABCIKOVO-NAGYM ARROEST (JUDGMENT)

by-case basis; and Hungary emphasized that no agreement was ever

reached with regard to the 1977 Treaty.

119. Hungary claimed that tbere was no rule of succession which
could operate in the present case to override the absence of consent.
Referring to Article 34 of the Vienna Convention of 23August 1978on

Succession of States in respect of Treaties, in which "a rule of automatic
succession to al1treaties is provided for", based on the principle of con-
tinuity, Hungary argued not only that it never signed or ratified the Con-
vention, but that the "concept of automatic succession" contained in that
Article was not and is not, and has never been accepted as, a statement of

general international 1aw.

Hungary further submitted that the 1977 Treaty did not create "obli-
gations and rights . . . relating to the régimeof a boundary" within the
meaning of Article II of that Convention, and noted that the existing
course of the boundary was unaffected by the Treaty. It also denied that

the Treaty was a "localized" treaty, or that it created rights "considered
as attaching to [the] territory" within the meaning of Article 12 of the
1978 Convention, which would, as such, be unaffected by a succession of
States. The 1977Treaty was, Hungary insisted, simply a joint investment.
Hungary's conclusion was that there is no basis on which the Treaty

could have survived the disappearance of Czechoslovakia so as to be
binding as between itself and Slovakia.

120. According to Slovakia, the 1977 Treaty, which was not lawfully
terminated by Hungary's notification in May 1992, remains in force

between itself, as successor State, and Hungary.
Slovakia acknowledged that there was no agreement on succession to
the Treaty between itself and Hungary. It relied instead, in the first place,
on the "general rule of continuity which applies in the case of dissolu-
tion"; it argued, secondly, that the Treaty is one "attaching to [the] ter-
ritory" within the meaning of Article 12of the 1978 Vienna Convention,

and that it contains provisions relating to a boundary.
121. In support of its first argument Slovakia cited Article 34 of the
1978 Vienna Convention, which it claimed is a statement of customary
international law, and which imposes the principle of automatic succes-
sion as the rule applicable in the case of dissolution of a State where the

~redecessor State has ceased to exist. Slovakia maintained that State
practice in cases of dissolution tends to support continuity as thele to
be followed with regard to bilateral treaties. Slovakia havingsucceeded
to part of the territory of the former Czechoslovakia, this would be the
rule applicable in the present case.
122. Slovakia's second argument rests on "the principle of ipso jure

continuity of treaties of a territorial or localized character". This rule,
Slovakia said, is embodied in Article 12of the 1978Convention, which in
part provides as follows:raux dont elles souhaitaient respectivement le maintien en vigueur entre
elles; et la Hongrie de souligner qu'aucun accord n'était intervenu au
sujet du traité de 1977.
119. La Hongrie a exposéqu'aucune règlede succession ne pouvait en
l'espècesuppléer à ce défaut de consentement.
Se référantà l'article 34 de la convention de Vienne du 23 août 1978

sur la succession d'Etats en matière de traités qui prévoit «une règle de
succession automatique à tous les traités)) sur la base du principe de
continuité, la Hongrie a fait valoir non seulement qu'elle n'avait jamais
signéou ratifiécette convention, mais aussi que <<leprincipe de succes-
sion automatique)) posédans cet article n'était, ni alors ni aujourd'hui,
I'énoncédu droit international général etqu'il n'avait jamais été reconnu

comme tel.
La Hongrie a également soutenu que le traité de 1977 n'avait pas créé
«[d']obligations et [de] droits ... se rapportant au régimed'une frontière))
au sens de l'article Il de cette convention et a relevéque le tracé actuel
de la frontière n'a pas étémodifié par le traité. Elle a aussi niéque le
traitéait un caractère «local» ou qu'il créedes droits ((considéréscomme

attachés [au] territoire)), au sens de l'article 12 de la convention de 1978,
et qui, en tant que tels, ne seraient pas affectés par une succession
d'Etats. La Hongrie a soutenu que le traité de 1977 prévoyait simple-
ment un investissement conjoint. Elle en a conclu qu'il n'existait aucune
base sur laquelle le traité aurait pu survivre la disparition de la Tchéco-

slovaquie et s'imposer ainsi dans les relations entre elle-mêmeet la Slo-
vaquie.
120. D'après la Slovaquie, le traité de 1977, qui n'a pas pris fin licite-
ment avec la notification hongroise de mai 1992, demeure en vigueur
entre elle-même,Etat successeur, et la Hongrie.
La Slovaquie a reconnu qu'aucun accord n'était intervenu entre elle et

la Hongrie quant à la succession au traité. Mais elle a, en premier lieu,
invoqué ((la règlegénéralede continuité qui s'applique en cas de dissolu-
tion)); et elle a, en second lieu, prétendu que le traitéétait«attach[é] [au]
territoire)), au sens de l'article 12de la convention de Vienne de 1978,et
qu'il contenait des dispositions relativesà une frontière.
121. A l'appui de son premier argument, la Slovaquie a cité l'article 34

de la convention de Vienne de 1978, qui, d'après elle, est l'énoncédu
droit international coutumier et fait dela succession automatique la règle
applicable en cas de dissolution d'un Etat lorsque 1'Etat prédécesseura
cesséd'exister. La Slovaquie a fait valoir que la pratique des Etats en cas
de dissolution tendait à confirmer que la continuité était larègleii suivre
en ce qui concerne les traités bilatéraux. La Slovaquie ayant succédé ii

une partie du territoire de l'ancienne Tchécoslovaquie, telle serait la règle
applicable en l'espèce.
122. Le deuxième argument de la Slovaquie repose sur «le principe de
la continuité ipsojure des traités de caractère territorial ou local)). Selon
la Slovaquie, cette règle est consacrée à l'article 12 de la convention de
1978 qui dispose notamment ce qui suit:71 GABCIKOVO-NAGYM PRR ECST(JUDGMENT)

"Article 12

Other Territorial Regimes
........................

2. A succession of States does not as such affect:
(a) obligations relating to the use of any territory, orto restrictions
upon its use, established by a treaty for the benefit of a group of

States or of al1States and considered as attaching to that terri-
tory;
(h) rights established by a treaty for the benefit of a group of States
or of al1 States and relating to the use of any territory, or to
restrictions upon its use, and considered as attaching to that
territory."

According to Slovakia, "[this] article [too] can be considered to be one
of those provisions of the Vienna Convention that represent the codifica-
tion of customary international law". The 1977 Treaty is said to fall

within its scoDe because of its "suecific characteristics . . . which ulace it
in the category of treaties of a localized or territorial character". Slovakia
also described the Treaty as one "which contains boundary provisions
and lays down a specific territorial régime" whichoperates in the interest
of al1Danube riparian States, and as "a dispositive treaty, creating rights
in rem, independently of the legal personality of its original signatories".

Here, Slovakia relied on the recognition by the International Law Com-
mission of the existence of a "special rule" whereby treaties "intended to
establish an objective régime" must be considered as binding on a suc-
cessor State (OfJicial Records of the United Nations Conferencc on the
Succession ofStutes in respect of Treaties, Vol.III,doc. AICONF.80I16I
Add.2, p. 34). Thus, in Slovakia's view, the 1977 Treaty was not one

which could have been terminated through the disappearance of one of
the original parties.

123. The Court does not find it necessary for the purposes of the
present case to enter into a discussion of whether or not Articl34 of the

1978 Convention reflects the state of customary international law. More
relevant to its present analysis is the particular nature and character of
the 1977Treaty. An examination of this Treaty confirms that, aside from
its undoubted nature as a joint investment, its major elements were the
proposed construction and joint operation of a large, integrated and indi-
visible complex of structures and installations on specific parts of the

respective territories of Hungary and Czechoslovakia along the Danube.
The Treaty also established the navigational régimefor an important sec-
tor of an international waterway, in particular the relocation of the main
international shipping lane to the bypass canal. In so doing, it inescap-
ably created a situation in which the interests of other users of the Dan- ((Article 12
Autres régirnes territoriuux

.............................
2. Une succession d'Etats n'affecte pas en tant que telle:

u) les obligations se rapportant à l'usage de tout territoire, ou aux
restrictions à son usage, établies par un traité au bénéficed'un
groupe d'Etats ou de tous les Etats et considéréescomme atta-
chéesà ce territoire;
b) les droits établispar un traité au bénéfice d'un groupe d'Etats ou
de tous les Etats et se rapportant à l'usage de tout territoire, ou

aux restrictions à son usage, et considéréscomme attachés à ce
territoire. »

Pour la Slovaquie: <<Onpeut voir dans [cet] article [aussi] I'une de ces
dispositions de la convention de Vienne qui codifient le droit internatio-
nal coutumier. )>Le traité de 1977 entrerait dans le champ d'application
de cette règleen raison de ses ((caractéristiques particulières ..., qui le pla-
cent dans la catégorie des traités de caractère local ou territorial)). La

Slovaquie a également affirméque le traité «cont[enait] des dispositions
établissant une frontière et ... établi[ssai]t un régimeterritorial particu-
lier)) dans l'intérête tous les Etats riverains du Danube; il s'agirait d'un
((traitédispositif créant des droits réels,indépendamment de la person-
nalitéjuridique des Etats qui l'ont signéà l'origine)). A cet égard,la Slo-
vaquie s'est fondée sur la reconnaissance, par la Commission du droit

international, de l'existence d'une «règle spéciale)), en vertu de laquelle
les traités «qui visent à créerdes régimesobjectifs))devaient êtreconsi-
déréscomme liant 1'Etatsuccesseur (Dot,urî~ents9f;fïciels de lu Confkr~mce
des Nutions Unies sur lu succession d'Etuts en mutiPrr de truitks, vol. III,
doc. A/CONF.80/16/Add.2, p. 35). Ainsi, de l'avis de la Slovaquie, le

traitéde 1977n'étaitpas de ceux qui auraient pu prendre fin du fait de la
disparition de I'une des parties d'origine.

123. La Cour ne juge pas nécessaire,aux fins de l'espèce,de discuter
du point de savoir si l'article 34 de la convention de 1978 reflèteou non

l'état du droit international coutumier. Pour son analyse actuelle, la
nature et le caractère particuliers du traité de 1977 présentent davantage
de pertinence. Un examen de ce traité confirme que ce dernier, outre qu'il
prévoit incontestablement un investissement conjoint, porte principale-
ment sur un projet de construction et d'exploitation conjointe d'un vaste
complexe intégréetindivisible d'ouvrages et d'installations surdes parties

bien définiesdes territoires respectifs de la Hongrie et de la Tchécoslova-
quie, le long du Danube. Le traité a aussi établi le régimede navigation
applicable à un tronçon important d'un cours d'eau international, notam-
ment en faisant désormais passer le chenal principal de navigation inter-
nationale par le canal de dérivation. Ce faisant, il a inévitablement créé72 GABCIKOVO-NAGYM PAOJOCT (JUDGMENT)

ube wereaffected. Furthermore, the interests of third States were expressly
acknowledged in Article 18, whereby the parties undertook to ensure
"uninterrupted and safe navigation on the international fairway" in
accordance with their obligations under the Convention of 18 August
1948concerning the Régimeof Navigation on the Danube.

In its Commentary on the Draft Articles on Succession of States in
respect of Treaties, adopted at itswenty-sixth session, the International
Law Commission identified "treaties of a territorial character" as having
been regarded both in traditional doctrine and in modern opinion as un-
affected by a succession of State(OfJicial Records of the United Nations

Conference on the Succession of States in respect of Treaties, Vol. III,
doc. A/CONF.80/16/Add.2, p. 27, para. 2). The draft text of Article 12,
which reflects this principle, was subsequently adopted unchanged in the
1978Vienna Convention. The Court considers that Article 12 reflects a
rule of customary international law; it notes that neither of the Parties
disputed this. Moreover, the Commission indicated that "treaties con-
cerning water rights or navigation on rivers are commonly regarded as
candidates for inclusion in the category of territorial treaties" (ibid.,
p. 33, para. 26). The Court observes that Article 12, in providing only,
without reference to the treaty itself, that rights and obligations of a ter-
ritorial character established by a treaty are unaffected by a succession of
States, appears to lend support to the position of Hungary ratherthan of
Slovakia. However the Court concludes that this formulation was devised

rather to take account of the fact that, in many cases, treaties which had
established boundaries or territorial régimes wereno longer in force
(ibid,pp. 26-37). Those that remained in force would nonetheless bind a
successor State.

Taking al1these factors into account, the Court finds that the content
of the 1977 Treaty indicates that it must be regarded as establishing a
territorial régimewithin the meaning of Article 12 of the 1978 Vienna
Convention. It created rights and obligations "attaching tomthe parts of
the Danube to which it relates; thus the Treaty itself cannot be affected
by a succession of States. The Court therefore concludes that the 1977
Treaty became binding upon Slovakia on 1 January 1993.
124. It might be added that Slovakia also contended that, while still a
constituent part of Czechoslovakia, it played aole in the development of

the Project, as it did later, in the most critical phase of negotiations with
Hungary about the fate of the Project. The evidence shows that the Slo-
vak Government passed resolutions prior to the signing of the 1977
Treaty in preparation for its implementation; and again, after signature,
expressing its support for the Treaty. It was the Slovak Prime Minister
who attended the meeting held in Budapest on 22 April 1991as the Pleni-
potentiary of the Federal Government to discuss questions arising out of
the Project.Itwas his successor as Prime Minister who notified his Hun- PROJET GAB~IKOVO-NAGYM(A ARRRSET) 72

une situation qui a une incidence sur les intérêdes autres utilisateurs du
Danube. De plus, les intérêtsd'Eta1.stiers ont étéexpressément reconnus
à son article 18, aux termes duquel les parties se sont engagéesaveillera
ce que «la navigation puisse se poursuivre de façon ininterrompue et
dans des conditions de sécuritédans le chenal international)),conformé-

ment aux obligations qui sont les leurs en vertu de la convention relative
au régimede la navigation sur le Danube du 18 août 1948.
Dans son commentaire sur le projet d'articles relatifs a la succession
d'Etats en matière de traités, adopté à sa vingt-sixième session, la Com-
mission du droit international a préciséque tant la doctrine traditionnelle
que les auteurs modernes considéraient qu'une succession d7Etats était

sans effet sur «les traités territoriaux» (Documentsoddicielsde la Confe-
rence des Nations Unies sur la succession d'Etats en matière de truitks,
vol. III, doc. A/CONF.80116/Add.2, p. 30, par. 2). Le projet d'article 12,
qui reflètece principe, a par la suite été repristel quel dans la convention
de Vienne de 1978. La Cour considère que l'article 12traduit une règlede

droit international coutumier; elle prend note de ce qu'aucune des Parties
ne le conteste. En outre, la Commission a indiquéque «les traités concer-
nant les droits sur les eaux ou la navigation fluviale sont généralement
considéréscomme pouvant être compris dans la catégoriedes traités ter-
ritoriaux))(ihid p,. 37, par. 26). La Cour fait observer que l'article 12,en
prévoyant seulement, sans se référerau traité lui-même,que les droits et

obligations de caractère territorial établis par un traité ne sont pas
affectéspar une succession d'Etats, pourrait sembler aller dans le sens de
la position de la Hongrie plutôt que dans celui de la position slovaque.
Néanmoins, la Cour conclut que ce libelléa en fait étéretenu pour tenir
compte de ce que, en de nombreux cas, les traités qui avaient établides
frontières ou des régimes territoriaux n'étaient plus en vigueur (ibid.,

p. 29-42). Ceux qui demeuraient en vigueur n'en devaient pas moins lier
I'Etat successeur.
Compte tenu de tous ces éléments,la Cour estime qu'au vu de son
contenu le traitéde 1977doit êtreconsidérécomme établissant un régime
territorial au sens de l'article 12 de la convention de Vienne de 1978. Il a

créédes droits et obligations «attachés» aux secteurs du Danube aux-
quels il se rapporte; ainsi, une successiond'Etats ne saurait avoir d'inci-
dence sur le traité lui-même.La Cour en conclut que le traité de 1977 lie
la Slovaquie depuis le Ierjanvier 1993.
124. Il peut être ajouté quela Slovaquie a également fait valoir que,
étant encore une partie constituante de la Tchécoslovaquie,elle a joué un

rôle aussi bien dans la mise au point du projet qu'ultérieurement dans la
phase la plus critique des négociations avec laHongrie sur le sort de celui-
ci. 11résultedu dossier que le Gouvernement slovaque a adopté des réso-
lutions avant la signature du traitéde 1977,pour en préparerl'application,
puis, après la signature, pour exprimer son attachement à celui-ci. C'est le
premier ministre slovaque qui a pris parta la réunion tenueà Budapest le

22 avril 1991 en tant que plénipotentiaire du gouvernement fédéralpour
discuter des questions afférentesau projet. C'est son successeur au poste de73 GABCIKOVO-NAGYM PROJES T(JL'DC~MENT)

garian counterpart by letter on 30 July 1991 of the decision of the Gov-
ernment of the Slovak Republic, as well as of the Government of the
Czech and Slovak Federal Republic, to proceed with the "provisional
solution" (see paragraph 63 above); and who wrote again on 18 Decem-
ber 1991 to the Hungarian Minister without Portfolio, renewing an

earlier suggestion that a joint commission be set up under the auspices of
the European Communities to consider possible solutions. The Slovak
Prime Minister also wrote to the Hungarian Prime Minister in May 1992
on the subject of the decision taken by the Hungarian Government to
terminate the Treaty, informing him of resolutions passed by the Slovak
Government in response.

It is not necessary, in the light of the conclusions reached in para-
graph 123above, for the Court to determine whether there are legal con-
sequences to be drawn from the prominent part thus played by the Slo-
vak Republic. Its role does, however, deserve mention.

125. TheCourt now turns to the other legal consequences arising from
its Judgment.
As to this, Hungary argued that future relations between the Parties, as
far as Variant C is concerned, are not governed by the 1977 Treaty. It
claims that it is entitled, pursuant to the Convention of 1976 on the
Regulation of Water Management Issues of Boundary Waters, to "50%

of the natural flow of the Danube at the point at which it crosses the
boundary below ~unovo" and considers that the Parties
"are obliged to enter into negotiations in order to produce the result

that the water conditions along the area from below Cunovo to
below the confluence at Sap becomejointly defined water conditions
as required by Article 3 (u) of the 1976 Convention".

Hungary moreover indicated that any mutually accepted long-term dis-
charge régimemust be "capable of avoiding damage, including especially
damage to biodiversity prohibited by the [1992 Rio Convention on Bio-
logical Diversity]". It added that "a joint environmental impact assess-

ment of the region and of the future of Variant C structures in the con-
text of the sustainable development of the region" should be carried out.

126. Hungary also raised the question of financial accountability for
the failure of the original project and stated that both Parties accept the
fact that the other has "proprietary and financial interests in the residues

of the original Project and that an accounting has to be carried out".
Furthermore, it noted that:
"Other elements of damage associated with Variant C on Hungar-

ian territory also have to be brought into the accounti...,as well
as electricity production since the diversion", PROJET GABCIKOVO-NAGYM(A ARORET) 73

premier ministre qui a notifiéà son homologue hongrois, par lettre du
30juillet 1991, ladécisiondu Gouvernement de la République slovaque et
celle du Gouvernement de la Républiquefédérativetchèque et slovaque de
recourir à la ((solution provisoire))(voir le paragraphe 63 ci-dessus); et c'est

lui qui a de nouveau écrit,le 18décembre1991, au ministre hongrois sans
portefeuille, pour réitérer laproposition de constituer. sous les auspices des
Communautés européennes, un comitémixte chargé d'examinerles solu-
tions possibles. Le premier ministre slovaque a également écritau premier
ministre hongrois en mai 1992 au sujet de la décisiondu Gouvernement
hongrois de mettre fin au traité, l'informantdes résolutionsque le Gouver-

nement slovaque avait adoptéesen réactionà cette décision.
Au vu des conclusions dégagéesau paragraphe 123 ci-dessus, point
n'est besoin pour la Cour de déterminer s'il y a lieu de tirer des consé-
quences juridiques du rôle marquant ainsi joué par la République slo-
vaque. II convenait toutefois de rappeler ce rôle.

125. La Cour en vient maintenant aux autres conséquencesjuridiques
de son arrêt.
A cet égard, la Hongrie a fait valoir que les relations futures entre les
Parties, en ce qui concerne la varianteC, ne sont pas régiespar le traité
de 1977.Elle prétend avoir droit, en vertu de la convention de 1976sur la

réglementation en matière d'eaux frontières, à ((cinquante pour cent du
débit naturel du Danube au point où iltraverse la frontière en aval de
Cunovo)) et considère que les Parties

«sont tenues d'engager des négociations de façon à parvenir au
résultat que"les conditions concernantle régimedes eaux de la zone
en aval de Cunovo jusqu'à l'aval du confluent à Sap deviennent des
conditions conjointement définies,comme le prescrit l'article 3 u) de
la convention de 1976)).

La Hongrie a en outre préciséqu'un régimede débità long terme accepté
d'un commun accord devait être«capable d'éviterdesdommages, y com-
pris en particulier des dommages à la biodiversitéqu'interdit la [conven-
tion de Rio de 1992 sur la diversité biologique])). Elle a ajouté qu'une

((évaluationconjointe de l'impact sur l'environnement ainsi que de l'ave-
nir des ouvrages de la variante C dans le cadre du développement durable
de la région))devrait êtreeffectuée.
126. La Hongrie a également soulevéla question des responsabilités
financières pour l'échecdu projet initial et a indiquéque les deux Parties

acceptent le fait que chacune a des ((intérêtspatrimoniaux et financiers
dans ce qui reste du projet initial, et qu'il faudra procéder à une évalua-
tion comptable)). Elle a observépar ailleurs que:

((D'autres élémentsdes dommages associésà la variante C en ter-
ritoire hongrois devront égalementêtrepris en compte ..., de même
que la production d'électricitédepuis le détournement du fleuve)),74 GABC~KOVO-NAGYMAROS PROJECT (JUDGMENT)

and that: "The overall situation is a complex one, and it may be most
easily resolved by some form of lump sum settlement."

127. Hungary stated that Slovakia had incurred international respon-
sibility and should make reparation for the damage caused to Hungary
by the operation of Variant C. In that connection, it referred, in the con-
text of reparation of the damage to the environment, to the rule of res-
titutio in integrum, and called for the re-establishment of "joint control

by the two States over the installations maintained as they are now", and
the "re-establishment of the flow of [the] waters to the level at which it
stood prior to the unlawful diversion of the river". It also referred to
reparation of the damage to the fauna, the flora, the soil, the sub-soil, the
groundwater and the aquifer, the damages suffered by the Hungarian

population on account of the increase in the uncertainties weighing on its
future (pretium doloris), and the damage arising from the unlawful use,
in order to divert the Danube, of installations over which the two Parties
exercised joint ownership.
Lastly, Hungary called for the "cessation of the continuous unlawful
acts" and a "guarantee that the same actions will not be repeated", and

asked the Court to order "the permanent suspension of the operation of
Variant Cm.
128. Slovakia argued for its part that Hungary should put an end to its
unlawful conduct and cease to impede the application of the 1977Treaty,
taking account of its "flexibility and of the important possibilities of

development for which it provides, or even of such amendments as might
be made to it by agreement between the Parties, further to future nego-
tiations". It stated that joint operations could resume on a basis jointly
agreed upon and emphasized the following:

"whether Nagymaros is built as originally planned, or built else-
where in a different form, or, indeed, not built at all, is a question to

be decided by the Parties some time in the future.

Provided the bypass canal and the Gabtikovo Power-station and
Locks - both part of the original Treaty, and not part of Variant C
- remain operational and economically viable and efficient, Slo-

vakia is prepared to negotiate over the future roles of Dunakiliti
and Cunovo, bearing Nagymaros in mind."

It indicated that the Gabtikovo power plant would not operate in peak
mode "if the evidence of environmental damage [was]clear and accepted
by both Parties". Slovakia noted that the Parties appeared to agree that

an accounting should be undertaken "so that, guided by the Court's find-
ings on responsibility, the Parties can try to reach a global settlement". It PROJET GABCIKOVO-NAGYM (ARRÊT) 74

et que: «La situation généraleest une situation complexe, et la façon la

plus simple d'y apporter une solution serait par le règlement d'une
somme forfaitaire. ))
127. La Hongrie a indiqué que la Slovaquie avait engagésa responsa-
bilitéinternationale et devait réparer les dommages subis par la Hongrie

du fait de la mise en Œuvre de la variante C. Elle s'est référéà cet égard,
dans le contexte de la réparation du dommage à I'environnement, à la
règle de la rrstitutio in integrum, et a demandé que soient rétablis le
((contrôleconjoint des deux Etats sur les installations conservées», ainsi

que le ((débitdes eaux au niveau qui était le sien avant le détournement
illicite du fleuve)). Elle a également évoquéla réparation des dommages
causésà la faune, à la flore, aux sols, aux sous-sols, à la nappe phréatique
et à l'aquifère, des dommages subis par la population hongroise du fait
de l'accroissement des incertitudes pesant sur son avenir (pretium dolo-

ris), ainsi que des dommages engendrés par l'utilisation illégale,aux fins
de détournement du Danube, des installations sur lesquelles les deux
Parties exerçaient une propriétéconjointe.
La Hongrie a enfin demandé la «cessation des faits illicites continus))

et la ((garantie de non-répétition desmêmesfaits)), la Cour étant ainsi
appelée à ordonner ((l'interruption définitive du fonctionnement de la
variante C ».
128. La Slovaquie a fait valoir pour sa part que la Hongrie devait

mettre un terme à son comportement illicite et cesser de faire obstacle
à l'application du traité de 1977, compte tenu de la ((flexibilité[du traité]
et des importantes possibilités d'évolution qu'il ménage, voire des mo-
difications qui pourraient lui être apportéespar accord entre les Parties
à la suite de négociations futures)). Elle a indiqué que des opérations

conjointes pourraient redémarrer sur une base convenue d'un commun
accord et soulignéce qui suit:

«que l'ouvrage de Nagymaros soit construit tel qu'il avait étéinitia-
lement prévu, ou qu'il soit construit ailleurs sous une autre forme,
ou mêmequ'il ne soit pas construit du tout, c'est une question dont

les Parties doivent décider, à un moment donné dans l'avenir.

Pourvu que le canal de dérivation et la centrale hydro-électrique
de GabCikovo et ses écluses -- qui font tous partie du traité d'ori-
gine, et non pas de la varianteC - demeurent opérationnels et éco-

nomiquement viables et efficaces, la Slovaquie est prête à négocier
au sujet du rôle futur de Duriakiliti et de Cunovo, tout en tenant
compte de Nagymaros. ))

Elle a préciséque la centrale de GabEikovo ne serait pas exploitée en
régimede pointe «si la preuve d'un dommage à I'environnement appa-

raissait clairement et était reconnue par les deux Parties. La Slovaquie a
observéque les Parties semblaient s'accorder sur la nécessitéde procéder
a une évaluation comptable, «de sorteque, guidéespar les conclusions deadded that the Parties would have to agree on how the sums due are to be
paid.

129. Slovakia stated that Hungary must make reparation for the
deleterious consequences of its failures to comply with its obligations,
"whether they relate to its unlawful suspensions and abandonments of
works or to its formal repudiation of the Treaty as from May 1992", and

that compensation should take the form of a rrstitutio in integrum. It
indicated that "Unless the Parties come to some other arrangement by
concluding an agreement, restitutio in integrurn ought to take the form of
a return by Hungary, ut a future tirne, to its obligations under the
Treaty" and that "For compensation to be 'full' . . ., to 'wipe out al1the
consequences of the illegal act' . .,a payment of compensation must . . .

be added to the rcstitutio .." Slovakia claims compensation which must
include both interest and loss of profits and should cover the following
heads of damage, which it offers by way of guidance:

(1) Losses caused to Slovakia in the GabCikovo sector: costs incurred
from 1990 to 1992 by Czechoslovakia in protecting the structures of
the GIN project and adjacent areas; the cost of maintaining the old
bed of the River Danube pending the availability of the new naviga-
tion canal, from 1990to 1992; losses to the Czechoslovak navigation
authorities due to the unavailability of the bypass canal from 1990to
1992 ; construction costs of Variant C (1990-1992).

(2) Losses caused to Slovakia in the Nagymaros sector: losses in the field
of navigation and flood protection incurred since 1992 by Slovakia
due to the failure of Hungary to proceed with the works.

(3) Loss of electricity production.

Slovakia also calls for Hungary to "give the appropriate guarantees
that it will abstain from preventing the application of the Treaty and the
continuous operation of the system". It argued from that standpoint that
it is entitled "to be given a formal assurance that the internationally

wrongful acts of Hungary will not recur':, and it added that "the main-
tenance of the closure of the Danube at Cunovo constitutes a guarantee
of that kind", unless Hungary gives an equivalent guarantee "within the
frameworkof the negotiations that are to take place between the Parties".

130. The Court observes that the part of its Judgment which answers
the questions in Article 2, paragraph 1, of the Special Agreement has a
declaratory character. 1t deals with the past conduct of the Parties and
determines the lawfulness or unlawfulness of that conduct between 1989
and 1992 as well as its effects on the existence of the Treaty.
131. Now the Court has, on the basis of the foregoing findings, tola Cour en matière de responsabilité, [elles]puissent s'efforcer de parvenir
à un règlement global)). Elle a ajoutéque les Parties devraient s'entendre
sur les modalités de paiement des sommes dues.
129. La Slovaquie a indiqué que la Hongrie devait réparer les consé-
quences dommageables de ses manquements, «qu'il s'agisse de ses sus-
pensions et abandons illicites de travaux ou de sa répudiation formelle du
traitéà partir de mai 1992», et que la réparation devait prendre la forme

d'une restitutio in integrum. Elle a préciséque cette dernière ((devrait se
traduire. sauf si les Parties en conviennent autrement Dar voie d'accord.
par la reprise par la Hongrie, ù l'avenir.,de ses obligations convention-
nelles)), et dit que: «Pour que la réparation soit «intégrale» ..., pour
qu'elle ((efface toutes les conséquences de l'acte illicite» ..., une indemni-
sation doit ... s'ujoutrra la rrstituti..» L'indemnisation que la Slova-

quie demande devrait inclure à la fois les intérêts etle manque a gagner et
devrait couvrir les chefs de préjudicesuivants, qu'elle a mentionnés à titre
indicatif:

1) Pertes causées a la Slovaquie dans le secteur de Gabëikovo: coûts
encourus de 1990 a 1992 par la Tchécoslovaquie pour protéger les
structures du projet GIN et des zones adjacentes; coût de l'entretien
de l'ancien lit du Danube jusqu'à ce que l'on dispose du nouveau
canal pour la navigation de 1990 à 1992; pertes encourues par les
autorités tchécoslovaques de navigation en raison de l'impossibilité
d'utiliser le canal de dérivation de 1990 à 1992; coûts de construction

de la variante C (1990-1992).
2) Pertes causées à la Slovaquie dans le secteur de Nagymaros: pertes
subies par la Slovaquie depuis 1992dans le domaine de la navigation
et de la protection contre les inondations du fait que la Hongrie n'a
pas poursuivi les travaux.
3) Perte de la production d'électricité.

Selon la Slovaquie, la Hongrie doit en outre «donner des garanties
appropriées de s'abstenir d'empêcher l'application du traité et le fonc-
tionnement continu du système)).Elle a fait valoir dans cette perspective
qu'elle est en droit ((d'obtenir l'assurance formelle que les faits interna-

tionalement illicites de la Hongrie ne se reproduiront pas)), et a ajouté
que «le maintien de la fermeture du Danube à Cunovo constitue une telle
garantie)), à moins qu'une assurance équivalente ne soit donnée par la
Hongrie «dans le cadre des négociations à intervenir entre les Parties)).

130. La Cour fait observer que la partie de l'arrêtoù elle répond aux
questions poséesau paragraphe 1 de l'article 2 du compromis revêtun
caractère déclaratoire. Elley traite du comportement pussédes parties et
détermine la licéitéou I'illicéitde ce comportement de 1989à 1992,ainsi
que ses effets sur l'existence du traité.
131. Il revient maintenant à la Cour, sur la base de ses conclusions76 GABCIKOVO-NAGYM PROROEST (JUDGMENT)

determine what the future conduct of the Parties should be. This part of
the Judgment is prescriptive rather than declaratory because it deter-

mines what the rights and obligations of the Parties are. The Parties will
have to seek agreement on the modalities of the execution of the Judg-
ment in the light of this determination, as they agreed to do in Article 5
of the Special Agreement.

132. In this regard it is of cardinal importance that the Court has
found that the 1977 Treaty is still in force and consequently governs the
relationship between the Parties. That relationship is also determined by

the rules of other relevant conventions to which the two States are party,
by the rules of general international law and, in this particular case, by
the rules of State responsibility; but it is governed, above all, by the
applicable rules of the 1977 Treaty as a les speciulis.
133. The Court, however, cannot disregard the fact that theTreaty has

not been fully implemented by either party for years, and indeed that
their acts of commission and omission have contributed to creating the
factual situation that now exists. Nor can it overlook that factual situa-
tion - or the practical possibilities and impossibilities to which it gives
rise- when deciding on the legal requirements for the future conduct of

the Parties.
This does not mean that facts - in this case facts which flow from
wrongful conduct - determine the law. The principle e.u injuriajus non
oritur is sustained by the Court's finding that the legal relationship

created by the 1977Treaty is preserved and cannot in this case be treated
as voided by unlawful conduct.
What is essential, therefore, is that the factual situation as it has devel-
oped since 1989 shall be placed within the context of the preserved and
developing treaty relationship, in order to achieve its object and purpose

in so far as that is feasible. For it is only then that the irregular state of
affairs which exists as the result of the failure of both Parties to comply
with their treaty obligations can be remedied.
134. What might have been a correct application of the law in 1989or

1992, if the case had been before the Court then, could be a miscarriage
ofjustice if prescribed in 1997.The Court cannot ignore the fact that the
GabEikovo power plant has bpen in operation for nearly five years, that
the bypass canal which feeds the plant receives its water from a signifi-
cantly smaller reservoir formed by a dam which is built not at Dunakiliti

but at Cunovo, and that the plant is operated in a run-of-the-river mode
and not in a peak hour mode as originally foreseen. Equally, the Court
cannot ignore the fact that, not only has Nagymaros not been built, but
that, with the effective discarding by both Parties of peak power opera-
tion, there is no longer any point in building it.

135. As the Court has already had occasion to point out, the 1977
Treaty was not only a joint investment project for the production of PROJET GABCIKOVO-NAGYMAROS (ARRÉT) 76

précédentes,d'établir quel devrait êtrele comportement des Parties à
lùvenir. La présentepartie de l'arrêtest plus normative que déclaratoire,
parce qu'elle définitles droits et obligations des Parties. C'est à la lumière
de cette définition que les Parties devront rechercher un accord sur les

modalités d'exécutionde l'arrêt,ainsi qu'elles en sont convenues à I'ar-
ticle 5 du compromis.

132. A cet égard, il est d'une importance primordiale que la Cour ait

constaté que le traité de 1977 est toujours en vigueur et régitpar consé-
quent les relations entre les Parties. Ces relations sont certes aussi sou-
mises aux règles des autres conventions pertinentes auxquelles les deux
Etats sont parties, aux règlesdu droit international généralet, en l'espèce,
aux règlesde la responsabilité des Etats; mais elles sont gouvernéesavant
tout par les règlesapplicables du traitéde 1977en tant que /ex speciulis.

133. La Cour ne saurait toutefois ignorer qu'aucune des parties n'a
pleinement exécutéle traitédepuis des années, ni d'ailleurs que les parties,
par leurs actes et leurs omissions, ont contribué à créerla situation de fait
qui prévaut aujourd'hui. En se prononçant sur les exigences auxquelles le
comportement à venir des Parties devra satisfaire en droit, la Cour ne
peut négligerde tenir compte de cette situation de fait et des possibilités

et impossibilités pratiques qui en résultent.
Cela ne signifie pas que les faits - en l'occurrence, des faits qui dé-
coulent de comportements illicites -- déterminent le droit. La Cour fait
droit au principe ex injuriujus non oritur lorsqu'elle conclut que les rela-
tions juridiques crééespar le traité de 1977 subsistent et ne sauraient en
l'espèceêtreconsidéréescomme annuléespar un comportement illicite.

C'est pourquoi iest essentiel de replacer la situation de fait, telle qu'elle
s'est développéedepuis 1989, dans le contexte de la relation convention-
nelle qui s'est maintenue et qui est appeléeà évoluer,afin de réaliserson
objet et son but dans toute la mesure du possible. Car ce n'est qu'à cette
condition qu'il pourra être portéremède rila situation irrégulièredue aux

manquements des deux Parties à leurs obligations conventionnelles.
134. Ce qui aurait pu êtreune application correcte du droit en 1989ou
1992, si l'affaire avait été soumiseà la Cour à l'époque,pourrait repré-
senter un mal-jugé en 1997. La Cour ne saurait ignorer le fait que la cen-
trale de GabEikovo fonctionne depuis près de cinq ans, que le canal de
dérivation qui alimente la centrale reçoit ses eaux d'un réservoir nette-

ment plus pe$t formé par un barrage qui n'a pas étéconstruit à Duna-
kiliti mais à Cunovo, et que la centrale est exploitéeau filde l'eau et non
en régimede pointe comme il était prévuà l'origine. La Cour ne saurait
pas davantage ne pas tenir compte de ce que non seulement l'ouvrage de
Nagymaros n'a pas étéconstruit,mais qu'il n'y a plus aucune raison de le
construire puisque les deux Parties ont, dans les faits, écarté l'hypothèse

d'une exploitation en régimede pointe.
135. Comme la Cour a déjàeu l'occasion de le souligner, le traité de
1977 ne prévoyait pas seulement un plan d'investissement conjoint pour77 GABC~KOVO-NAGYM PAOJOCT (JUDGMENT)

energy, but it was designed to serve other objectives asell: the improve-
ment of the navigability of the Danube, flood control and regulation of

ice-discharge, and the protection of the natural environment. None of
these objectives has been given absolute priority over the other, in spite
of the emphasis which is given in the Treaty to the construction of a
System of Locks for the production of energy. None of them has lost its
importance. In order to achieve these objectives the parties accepted obli-

gations of conduct, obligations of performance, and obligations of result.

136. It could be said that that part of the obligations of performance
which related to the construction of the System of Locks - in so far as

they were not yet implemented before 1992 - have been overtaken by
events. It would be an administration of the law altogether out of touch
with reality if the Court were to order those obligations to be fully re-
instated and the works at Cunovo to be demolished when the objectives
of the Treaty can be adequately served by the existing structures.

137. Whether this is indeed the case is, first and foremost, for the
Parties to decide. Under the 1977 Treaty ils several objectives must be
attained in an integrated and consolidated programme, to be developed
in the Joint Contractual Plan. The Joint Contractual Plan was, until

1989, adapted and amended frequently to better fit the wishes of the
parties. This Plan was also expressly described as the means to achieve
the objectives of maintenance of water quality and protection of the envi-
ronment.
138. The 1977 Treaty never laid down a rigid system, albeit that the

construction of a system of locks at GabEikovo and Nagymaros was pre-
scribed by the Treaty itself. In this respect, however, the subsequent posi-
tions adopted by the parties should be taken into consideration. Not only
did Hungary insist on terminating construction at Nagymaros, but

Czechoslovakia stated, on various occasions in the course of negotia-
tions, that it was willing to consider a limitation or even exclusion of
operation in peak hour mode. In the latter case the construction of the
Nagymaros dam would have become pointless. The explicit terms of the
Treaty itself were therefore in practice acknowledged by the parties to be

negotiable.
139. The Court is of the opinion that the Parties are under a legal obli-
gation, during the negotiations to be held by virtue of Article 5 of the
Special Agreement, to consider, within the context of the 1977Treaty, in
what way the multiple objectives of the Treaty can best be served, keep-

ing in mind that al1of them should be fulfilled.
140. It is clear that the Project's impact upon, and its implications for,
the environment are of necessity a key issue. The numerous scientific
reports which have been presented to the Court by the Parties - even if

their conclusions are often contradictory - provide abundant evidence
that this impact and these implications are considerable.
In order to evaluate the environmental risks, current standards must be
taken into consideration. This is not only allowed by the wording of PROJET GABCIKOVC)-NAGYMAROS (ARRET) 77

la production d'énergie,mais servait égalementd'autres objectifs: I'amé-
lioration de la navigation sur le Danube, la maîtrise des crues, la régula-
tion de l'évacuation des glaces et la protection de l'environnement natu-
rel. Aucun de ces objectifs ne s'est vu accorder de priorité absolue par

rapport aux autres, bien que le traité mette l'accent sur la construction
d'un système d'éclusesen vue de la production d'énergie.Aucun d'entre
eux n'a perdu de son importance. Pour les atteindre, les parties ont
accepté d'assumer des obligations de comportement, des obligations de
faire et des obligations de résultat.
136. On pourrait dire que parnii les obligations de faire, celles ayant

trait à la construction du système d'écluses - dans la mesure où elles
n'avaient pas encore étéexécutéesavant 1992 - ont été dépasséepsar les
événements.La Cour appliquerait le droit en perdant entièrement de vue
la réalitési elle devait ordonner leplein rétablissement de ces obligations
et la démolition des ouvrages de Cunovo, alors que les structures exis-
tantes peuvent adéquatement servir la réalisation des objectifs du traité.

137. C'est d'abord et avant tout aux Parties de décidersi tel est bien le
cas. Le traitéde 1977 prévoyait que ses différentsobjectifs devraient être
atteints par l'effet d'un programme intégré et consolidé,qui devait être
précisédans le plan contractuel conjoint. Ce dernier a étéj,usqu'en 1989,
fréquemment adapté et amendépour mieux tenir compte des souhaitsdes
parties. Ce plan a aussi étéexplicitement décritcomme le moyen de réa-

liser les objectifs que sont le maintien de la qualité de l'eau et la protec-
tion de l'environnement.
138. Le traitéde 1977 n'ajamais prévu un systèmerigide, bien qu'il ait
lui-même rescritla construction d'un svstème d'éclusesà Gabtikovo et à
Nagymaros. A cet égard, toutefois, il convient de prendre en considéra-
tion les positions adoptées ultérieurement par les parties. Non seulement

la Hongrie a insistépour mettre fin aux travaux de construction à Nagy-
maros. mais la Tchécoslovaauie a affirméà différentes remises au cours
des négociations qu'elle était disposée à envisager une limitation, voire
l'abandon, de l'exploitation en régime de pointe. Dans cette dernière
hypothèse, la construction du barrage de Nagymaros serait devenue inu-
tile. Les parties ont donc reconnu en pratique que les termes exprès du

traité lui-même étaientnégociables.
139. La Cour est d'avis que les Parties sont juridiquement tenues, au
cours des négociations qu'elles mimeront en application de l'article 5 du
compromis, d'envisager dans le contexte du traitéde 1977de quelle façon
elles peuvent servir au mieux les objectifs multiples du traité, en gardant
à l'esprit qu'ils devraient tous êtreatteints.

140. Il est clair que les incidences du projet sur l'environnement et ses
implications pour celui-ci seront nécessairement une question clef. Les
nombreux rapports scientifiques présentés à la Cour par les Parties,
mêmesi leursconclusions sont souvent contradictoires, fournissent ample-
ment la preuve que ces incidences et ces implications sont considérables.

Aux fins de l'évaluation des risques écologiques, ce sont les normes
actuelles qui doivent êtreprises en considération. Non seulement le libelléArticles 15 and 19, but even prescribed, to the extent that these
articles impose a continuing - and thus necessarily evolving - obliga-
tion on the parties to maintain the quality of the water of the Danube

and to protect nature.
The Court is mindful that, in the field of environmental protection,
vigilance and prevention are required on account of the often irreversible
character of damage to the environment and of the limitations inherent
in the very mechanism of reparation of this type of damage.

Throughout the ages, mankind has, for economic and other reasons,
constantly interfered with nature. In the past, this was often done with-
out consideration of the effects upon the environment. Owing to new
scieritificinsights and to a growing awareness of the risks for mankind -

for present and future generations - of pursuit of such interventions at
an unconsidered and unabated pace, new norms and standards have been
developed, set forth in a great number of instruments during the last two
decades. Such new norms have to be taken into consideration, and such
new standards given proper weight, not only when States contemplate

new activities but also when continuing with activities begun in the past.
This need to reconcile economic development with protection of the envi-
ronment is aptly expressed in the concept of sustainable development.

For the purposes of the present case, this means that the Parties
together should look afresh at the effects on the environment of the
operation of the GabCikovo power plant. In particular they must find a
satisfactory solution for the volume of water to be released into the old
bed of the Danube and into the side-arms on both sides of the river.

141. It is not for the Court to determine what shall be the final result
of these negotiations to be conducted by the Parties. It is for the Parties
themselves to find an agreed solution that takes account of the objectives
of the Treaty, which must be pursued in a joint and integrated way, as
well as the norms of international environmental law and the principles

of the law of international watercourses. The Court will recall in this con-
text that, as it said in the North Seu Continental Shelfcases:

"[the Parties] are under an obligation so to conduct themselves that
the negotiations are meaningful, which will not be the case when
either of them insists upon its own position without contemplating
any modification of it" (I.C.J. Reports 1969, p. 47, para. 85).

142. What is required in the present case by the rule puctu sunt ser-
vanda, as reflected in Article 26 of the Vienna Convention of 1969on the

Law of Treaties, is that the Parties find an agreed solution within the co-
operative context of the Treaty.
Article 26 combines two elements, which are of equal importance. It
provides that "Every treaty in force is binding upon the parties to it and PROJET GABC~KOVO-NAGYM ARRROST) 78

des articles15 et 19 le permet, mais il le prescrit mêmedans la mesure où
ces articles mettent à la charge des parties une obligation continue, et
donc nécessairement évolutive,de maintenir la qualitéde l'eau du Danube

et de protéger la nature.
La Cour ne perd pas de vue que, dans le domaine de la protection de
I'environnement, la vigilance et la prévention s'imposent en raison du
caractère souvent irréversibledes dommages causésà l'environnement et
des limites inhérentes au mécanisme mêmede réparation de ce type de

dommages.
Au cours des âges, l'homme n'a cesséd'intervenir dans la nature pour
des raisons économiques et autres. Dans le passé,il l'a souvent fait sans
tenir compte des effets sur I'environnement. Grâceaux nouvelles perspec-
tives qu'offre la science et à une conscience croissante des risques que la
poursuite de ces interventions a un rythme inconsidéréet soutenu repré-

senterait pour l'humanité - qu'il s'agisse des générations actuelles ou
futures -, de nouvelles normes et exigences ont étémises au point, qui
ont été énoncéedsans un grand nombre d'instruments au cours des deux
dernières décennies.Ces normes nouvelles doivent êtreprises en considé-
ration et ces exigences nouvelles convenablement appréciées non seule-

ment lorsque des Etats envisagent de nouvelles activités, mais aussi
lorsqu'ils poursuivent des activités qu'ilsont engagéesdans le passé. Le
concept de développement durable traduit bien cette nécessitéde conci-
lier développement économique et protection de I'environnement.
Aux fins de la présente espèce, cela signifie que les Parties devraient,
ensemble, examiner à nouveau leseffets sur I'environnement de I'exploita-

tion de la centrale de GabEikovo. En particulier, elles doivent trouver une
solution satisfaisante en ce qui concerne le volume d'eau a déverserdans
l'ancien lit du Danube et dans les bras situésde part et d'autre du fleuve.
141. Il n'appartient pas à la Cour de déterminer quel sera le résultat
final des négociations à mener par les Parties. Ce sont les Parties elles-

mêmes qui doivent trouver d'un commun accord une solution qui tienne
compte des objectifs du traité -- qui doivent être atteints de façon
conjointe et intégrée - de mêmeque des normes du droit international
de l'environnement et des principes du droit relatif aux cours d'eau inter-
nationaux. La Cour rappellera dans ce contexte ce qu'elle a dit dans les

affaires du Pluteau continentul de lu mer du Nord:
«les parties ont l'obligation de se comporter de telle manière que la

négociation ait un sens, ce qui n'est pas le cas lorsque l'une d'elles
insiste sur sa propre position sans envisager aucune modification))
(C.I.J. Recueil 1969, p. 47, par. 85).

142. Ce que la règlepactu sunt srri1unda,telle que reflétéa l'article 26
de la convention de Vienne de 1969 sur le droit des traités, exige en
l'espècedes Parties, c'est de trouver d'un commun accord une solution
dans le cadre de coopération que prévoit le traité.
L'article 26 associe deux éléments,qui sont d'égaleimportance. II dis-

pose que: «Tout traité en vigueur lie les parties et doit êtreexécutépar79 GABCIKOVO-NAGYM PRORECST (JUDGMENT)

must be performed by them in good faith." This latter element, in the
Court's view, implies that, in this case, it is the purpose of the Treaty, and
the intentions of the parties in concluding it, which should prevail over

its literal application. The principle of good faith obliges the Parties to
apply it in a reasonable way and in such a manner that its purpose can be
realized.
143. During this dispute both Parties have called upon the assistance
of the Commission of the European Communities. Because of the dia-
metrically opposed positions the Parties took with regard to the required

outcome of the trilateral talks which were envisaged, those talks did not
succeed. When, after the present Judgment is given, bilateral negotiations
without pre-conditions are held, both Parties can profit from the assist-
ance and expertise of a third party. The readiness of the Parties to accept
such assistance would be evidence of the good faith with which they con-

duct bilateral negotiationsin order to give effect to the Judgment of the
Court.
144. The 1977Treaty not only contains ajoint investment programme,
it also establishes a régime.According to the Treaty, the main structures
of the System of Locks are the joint property of the Parties;their opera-
tion will take the form of a co-ordinated single unit; and the benefits of

the project shall beequally shared.
Since the Court has found that the Treaty is still in force and that,
under its terms, the joint régime is a basic element, it considers that,
unless the Parties agree otherwise, such a régimeshould be restored.

145. Article 10, paragraph 1, of the Treaty states that works of the
System of Locks constituting the joint property of the contracting parties
shall be operated, as a co-ordinated single unit and in accordance with
jointly agreed operating and operational procedures, by the authorized
operating agency of the contracting party in whose territory the works

are built. Paragraph 2 of that Article states that works on the System of
Locks owned by one of the contracting parties shall be independently
operated or maintained by the agencies of that contracting party in the
jointly prescribed manner.
The Court is of the opinion that the works at ~unovo should become
a jointly operated unit within the meaning of Article 10, paragraph 1, in

view of their pivotal role in the operation of what rem+ of the Project
and for the water-management régime. The dam at Cunovo has taken
over the role which was originally destined for the works at Dunakiliti,
and therefore should have a similar status.
146. The Court also concludes that Variant C, which it considers oper-

ates in a manner incompatible with the Treaty, should be made to con-
form to it. By associating Hungary, on an equal footing, in its operation,
management and benefits, Variant C will be transformed from a defacto
status into a treaty-based régime.

It appears from various parts of the record that, given the current state PROJET GABCIKOVO-NAGYM(A ARRRSÉT) 79

elles de bonne foi.» De l'avis de la Cour, ce dernier élémentimplique
qu'au cas particulier c'est le but du traité, et l'intention dans laquelle les
parties ont conclu celui-ci, qui doivent prévaloir sur son application lit-
térale. Le principe de bonne foi oblige les Parties à l'appliquer de façon
raisonnable et de telle sorte que son but puisse être atteint.

143. Au cours de ce différend, les deux Parties ont sollicitél'aide de la
Commission des Communautés européennes. Du fait que les Parties ont
adopté des positions diamétralement opposées sur le point de savoir ce
que devait êtrele résultat des pourparlers trilatéraux qui étaient envisa-
gés, ceux-ciont échoué. Lorsque,une fois le présentarrêt rendu, les deux
Parties engageront des négociations bilatérales sans conditions préa-

lables, elles pourront bénéficierde l'assistance et de l'expertise d'une
tierce partie. L'acceptation d'une telle aide par les Parties attesterait de
la bonne foi marquant les négociations bilatérales qu'ellesmèneront pour
donner effet à l'arrêtde la Cour.
144. Le traitéde 1977 ne prévoit pas seulement un programme d'inves-
tissement conjoint, ilétablit aussi un régime. Selon le traité, les princi-

paux ouvrages du système d'éclusessont la propriétéconjointedes parties;
ils seront gérés entant qu'unité unique coordonnée; et les bénéficesdu
projet seront partagés à parts égales.-
Puisque la Cour a conclu que le traitéest toujours en vigueur et qu'aux
termes de celui-ci le régimeconjoint en est un élémentfondamental, elle
est d'avis qu'à moins que les Parties n'en disposent autrement un tel
régimedevrait êtrerétabli.

145. Le paragraphe 1 de l'article 10 du traité dispose que les ouvrages
du systèmed'éclusesconstituant la propriétécommunedes parties contrac-
tantes seront gérés,n tant qu'unité coordonnée et conformément aux pro-
cédures opérationnelles arrêtées d'uncommun accord, par l'organisme de
gestion agrééde la partie contractante sur le territoire de laquelle les
ouvrages auront été construits. Le paragraphe 2 du mêmearticle énonce

que les ouvrages du système d'éclusesappartenant à l'une des parties con-
tractantes seront gérésou entretenus indépendamment par les organismes
de cette partie selon des modalités arrêtées d'uncommun accord.
La Cour estime que les ouvrages de Cunovo devraient devenir une
unité exploitée conjointement au sens du paragraphe 1 de l'article 10,
compte tenu de leur rôle central dans le fonctionnement de ce-qui reste

du projet et dans le régimede gestion des eaux. Le barrage de Cunovo a
assuméle rôle qui avait étéprévuà l'origine pour les ouvrages de Duna-
kiliti, eildevrait donc bénéficierd'un statut analogue.
146. La Cour conclut également que la variante C, qu'elle a estimé
fonctionner d'une manière incompatible avec le traité, devrait êtremise
en conformité avec ce dernier. L'association de la Hongrie, sur un pied
d'égalité,à l'exploitation, à la gestion et aux bénéficesde la variante C,

aura pour effet que le statut de fait qui s'applique à cette dernière fera
place a un régimeconventionnel.
Il ressort des différents élémentsdu dossier qu'en l'état actuel des PROJET GABCIKOVO-NAGYMAROS (ARRÊT) 80

informations soumises a la Cour la variante C semble ouv voirfonction-
ner d'une façon qui permette à la fois l'exploitation économique du sys-
tèmede production d'électricitéet la satisfaction des préoccupations éco-
logiques essentielles.

Régulariser la variante C en en faisant une partie intégrante d'un sys-
tème d'ouvrages opérationnel unique et indivisible apparaît également
nécessairepour donner de nouveau effet à l'article 9 du traité, qui prévoit
que les parties contractantes participeront,à parts égales,à l'utilisation et
aux avantages du système d'écluses.
147. Le rétablissement du régimeconjoint refléteraaussi de façon opti-
male le concept d'une utilisation conjointe des ressources en eau parta-

géespour atteindre les différents objectifsmentionnés dans le traitéet ce,
conformément au paragraphe 2 de l'article 5 de la convention sur le droit
relatif aux utilisations des cours d'eau internationaux à des fins autres
que la navigation, aux termes duquel:

«Les Etats du cours d'eau participent à l'utilisation, à la mise en
valeur et a la protection d'un cours d'eau international de manière
équitable et raisonnable. Cette participation comporte à la fois le
droit d'utiliser le cours d'eau et le devoir de coopérer à sa protection
et à sa mise en valeur, comine prévu dans les présents articles.))

(Assemblée générale, doc. A/5;11869du 11 avril 1997.)

148. Jusqu'ici, la Cour a indiqué quels devraient être, d'après elle, les
effets de sa décision suivant laquelle le traité de 1977 est toujours en
vigueur. Elle en vient maintenant aux conséquences juridiques des actes
internationalement illicites commis par les Parties.
149. Dans son arrêtdu 13septembre 1928en l'affaire relative à l'Usine

de Cho~zu~t, a Cour permanente de Justice internationale a dit:
«la réparation doit, autant que possible, effacer toutes les consé-
quences de l'acte illicite et rétablir l'état qui aurait vraisemblable-

ment existési ledit acte n'avait pas étécommis)) (C.P.J.I.série A
no 17, p. 47).
150. La réparation doit ((autant que possible)) effacer toutes les consé-

quences de l'acte illicite. En l'espèce, les conséquences des actes illicites
commis par les deux Parties seront effacées«autant que possible)) si ces
dernières reprennent leur coopération pour l'utilisation des ressources en
eau partagées du Danube et si le programme pluridimensionnel d'utilisa-
tion, de mise en valeur et de protection du cours d'eau, en tant qu'unité
unique coordonnée, est réaliséde manière équitable et raisonnable. Ce
que peuvent faire les Parties, c'est rétablir une gestion conjointe de ce qui

reste du projet. A cette fin, il leur est loisible, d'un commun accord, de
conserver les ouvrages de Cunovo, en apportant des changements dans le
mode d'exploitation du système pour ce qui est de la répartition de l'eau
et de l'électricité,et de ne pas construire les ouvrages de Nagymaros. 151. The Court has been asked by both Parties to determine the con-
sequences of the Judgment as they bear upon payment of damages.
According to the Preamble to the Special Agreement, the Parties agreed
that Slovakia is the sole successor State of Czechoslovakia in respect of

rights and obligations relating to the GabCikovo-Nagymaros Project.
Slovakia thus may be liable to pay compensation not only for its own
wrongful conduct but also forthat of Czechoslovakia, and it isentitled to
be compensated for the damage sustained by Czechoslovakia as well as
by itself as a result of the wrongful conduct of Hungary.

152. The Court has not been asked at this stage to determine the quan-
tum of damages due, but to indicate on what basis they should be paid.
Both Parties claimed to have suffered considerable financial losses and
both claim pecuniary compensation for them.
It is a well-established rule of international law that an injured State is
entitled to obtain compensation from the State which has committed an

internationally wrongful act for the damage caused by it. In the present
Judgment, the Court has concluded that both Parties committed interna-
tionally wrongful acts, and it has noted that those acts gave rise to the
damage sustained by the Parties; consequently, Hungary and Slovakia
are both under an obligation to pay compensation and are both entitled
to obtain compensation.

Slovakia is accordingly entitled to compensation for the damage suf-
fered by Czechoslovakia as well as by itself as a result of Hungary's deci-
sion to suspend and subsequently abandon the works at Nagymaros and
Dunakiliti, as those actions caused the postponement of the putting into
operation of the GabCikovo power plant, and changes in its mode of
operation once in service.

Hungary is entitled to compensation for the damage sustained as a
result of the diversion of the Danube, since Czechoslovakia, by putting
into operation Variant C, and Slovakia, in maintaining it in service,
deprived Hungary of its rightful part in the shared water resources, and
exploited those resources essentially for their own benefit.
153. Given the fact, however, that there have been intersecting wrongs

by both Parties, the Court wishes to observe that the issue of compen-
sation could satisfactorily be resolved in the framework of an overall
settlement if each of the Parties were to renounce or cancel al1financial
claims and counter-claims.
154. At the same time, the Court wishes to point out that the settle-
ment of accounts for the construction of the works is different from the

issue of compensation, and must be resolved in accordance with the 1977
Treaty and related :instruments. If Hungary is to share in the operation
and benefits of the Cunovo complex, it must pay a proportionate shareof
the building and running costs. PROJETGAB~IKOVO-NAGYM(A ARORÊT) 8 1

151. La Cour a étépriéepar les deux Parties de déterminer les consé-
quences de son arrêten ce qui est du paiement de dommages et intérêts.
Aux termes du préambule du compromis, les Parties sont convenues que
la Slovaquie est l'unique Etat successeur de la Tchécoslovaquie en ce qui
concerne les droits et obligations relatifs au projet GabCikovo-Nagyma-
ros. La Slovaquie peut donc êtretenue de verser des indemnités, non seu-
lement pour ses propres faits illicites, mais aussi pour ceux de la Tché-

coslovaquie, et elle a le droit d'êtreindemniséedes dommages subis tant
par la Tchécoslovaquie que par elle-même enraison du comportement
illicite de la Hongrie.
152. La Cour n'a pas étépriéeà ce stade de déterminer le montant des
dommages et intérêtsdus, mais d'indiquer sur quelle base ils doivent être
versés. Les deux Parties ont prétendu avoir subi des pertes financières

considérables et elles demandent toutes deux à en êtreindemnisées.
II est une règlebien établiedu droit international, qu'un Etat léest en
droit d'êtreindemnisé,par I'Etat auteur d'un fait internationalement illi-
cite, des dommages résultant de celui-ci. Dans le présent arrêt,la Cour a
conclu aue les deux Parties avaient commis des actes internationalement
illicites et elle a constaté que ceux-ci sanl'origine des dommages subis

par les Parties; en conséquence, la Hongrie et la Slovaquie sont toutes
deux tenues de verser des indemnités et sont toutes deux en droit d'en
recevoir.
La Slovaquie est donc en droit d'êtreindemniséedes dommages subis
tantpar la Tchécoslovaquie que par elle-mêmedu fait de la décisionhon-
groise de suspendre puis d'abandonner les travaux à Nagymaros et à
Dunakiliti, car ces agissements ont occasionnéle report de la mise en ser-

vice de la centrale de GabCikovo el, une fois celle-ci mise en service, des
changements dans son mode de fonctionnement.
La Hongrie est en droit d'êtreindemniséedes dommages qu'elle a subis
du fait du détournement du Danube car la Tchécoslovaquie, en mettant
en service la varianteC, et la Slovaquie, en la maintenant en service, ont
privéla Hongrie de sa part légitimede ressources en eau partagées et ont

exploitéces ressources essentiellement à leur profit.
153. Toutefois. compte tenu de ce que les Parties ont commis des actes
illicites croisés, la Cour tient à faire observer que la question de l'in-
demnisation pourrait être résolue de façon satisfaisante, dans le cadre
d'un règlement d'ensemble, si chacune des Parties renonçait à toutes ses
demandes et contre-demandes d'ordre financier ou les annulait.

154. La Cour tient en même temps à souligner que le règlement des
comptes concernant la construction des ouvrages est une question dis-
tincte de celle de l'indemnisation et doit êtreeffectuéconformément au
traité de 1977 et aux instruments y afférents. Si la Hongrie participe à
l'exploitation du complexe de Cunovo et reçoit sa part de bénéfices, elle
devra payer- une part proportionnelle des coûts de construction et de
fonctionnement.82 GABCIKOVO-NAGYMAROS PROJECT (JUDGMENT)

155. For these reasons,

(1) Having regard to Article 2, paragraph 1, of the Special Agreement,

A. By fourteen votes to one,

Finds that Hungary was not entitled to suspend and subsequently
abandon, in 1989, the works on the Nagymaros Project and on the
part of the GabCikovo Project for which the Treaty of 16 September

1977 and related instruments attributed responsibility to it;

IN FAVOUK : Pre.~identSchwebel; Vice-Prrsident Weeramantry ; Judges
Oda, Bedjaoui, Guillaume, Ranjeva, Shi, Fleischhauer, Koroma,

Vereshchetin, Parra-Aranguren, Kooijmans, Rezek; Judge ad hoc
Skubiszewski ;
AGAINSJ Tu:dge Herczegh;

B. By nine votes to six,

Finds that Czechoslovakia was entitled to proceed, in November
1991, to the "provisional solution" as described in the terms of the
Special Agreement ;

IN FAVOUR : Vice-President Weeramantry ;Judges Oda, Guillaume, Shi,
Koroma, Vereshchetin, Parra-Aranguren, Kooijmans; Judge ad hoc
Skubiszewski ;

AGAINST : President Schwebel ; Judges Bedjaoui, Ranjeva, Herczegh,
Fleischhauer, Rezek;

C. By ten votes to five,
Finds that Czechoslovakia was not entitled to put into operation,

from October 1992, this "provisional solution";
IN FAVOUR : President Schwebel ; Vice-President Weeramantry ;Judges
Bedjaoui, Guillaume, Ranjeva, Herczegh, Shi, Fleischhauer, Kooij-

mans, Rezek;
AGAINST Ju:dges Oda, Koroma, Vereshchetin, Parra-Aranguren; Judge
ad hoc Skubiszewski;

D. By eleven votes to four,

Finds that the notification, on 19 May 1992, of the termination of
the Treaty of 16 September 1977 and related instruments by Hungary
did not have the legal effect of terminating them;

IN FAVOUR:Vice-Pre~ident Weeramantry; Judges Oda, Bedjaoui,
Guillaume, Ranjeva, Shi, Koroma, Vereshchetin, Parra-Aranguren,
Kooijmans; Judge ad hoc Skubiszewski;

AGAINST : President Schwebel ;Judgrs Herczegh, Fleischhauer, Rezek ; PROJET GABCIKOVO-NAGYMAROS (ARRÊT)

155. Par ces motifs,

1) Vu le paragraphe 1 de l'article 2 du compromis.

A. Par quatorze voix contre une,

Dit que la Hongrie n'était pas en droit de suspendre puis d'aban-
donner, en 1989, les travaux relatifs au projet de Nagymaros ainsi
qu'à la partie du projet de GabCikovo dont elle était responsable
aux termes du traité du 16 septembre 1977 et des instruments y affé-
rents;

POUR:M. Schwebel, Président; M. Weeramantry, Vice-Président;
MM. Oda, Bedjaoui, Guillaume, Ranjeva, Shi, Fleischhauer,
Koroma, Vereshchetin, Parra-Aranguren, Kooijmans, Rezek, juges;
M. Skubiszewski,juge ad hoc;
CONTRE M:. Herczegh,juge:

B. Par neuf voix contre six,

Dit que la Tchécoslovaquie était en droit de recourir, en novembre
1991, à la «solution provisoire)) telle que décrite aux termes du com-

promis :
POUR:M. Weeramantry, Vice-président;MM. Oda, Guillaume, Shi,
Koroma. Vereshchetin, Parra-Aranguren, Kooijmans, juges;
M. Skubiszewski,juge ad hoc;

CONTREM : . Schwebel, Président; MM. Bedjaoui, Ranjeva, Herczegh,
Fleischhauer, Rezek,juges;

C. Par dix voix contre cinq,

Dit que la Tchécoslovaquie n'étaitpas en droit de mettreen service,
à partir d'octobre 1992, cette ((solution provisoire)) ;
POUR:M. Schwebel, Président; M. Weeramantry, Vice-président;
MM. Bedjaoui, Guillaume, Ranjeva, Herczegh, Shi, Fleischhauer.

Kooijmans, Rezek,juges;
CONTRE: MM. Oda, Koroma, Vereshchetin, Parra-Aranguren, juges;
M. Skubiszewski,juge ad hoc;

D. Par onze voix contre quatre,

Dit que la notification, le 19 mai 1992, de la terminaison du traité
du 16septembre 1977 etdes instruments y afférents par laHongrie n'a
pas eu pour effet juridique d'y mettre fin;

POUR:M. Weeramantry, Vice-Présiden tMM. Oda, Bedjaoui,Guillaume,
Ranjeva, Shi, Koroma, Vereshchetin, Parra-Aranguren, Kooijmans,
juges; M. Skubiszewski,juge ad hoc;
CONTRE: M. Schwebel, Président;MM. Herczegh, Fleischhauer, Rezek,
juges;Having regard to Article 2, paragraph 2,and Article 5 of the Special
Agreement,

A. By twelve votes to three,

Finds that Slovakia, as successor to Czechoslovakia, became a
party to the Treaty of 16 September 1977 as from 1 January 1993;

IN FAVOUR : President Schwebel ; Vice-President Weeramantry ; Judges
Oda, Bedjaoui, Guillaume, Ranjeva. Shi, Koroma, Vereshchetin,
Parra-Aranguren, Kooijmans: Judge ad hoc Skubiszewski;
AGAINSJ Tu:dges Herczegh, Fleischhauer, Rezek ;

B. By thirteen votes to two,

Finds that Hungary and Slovakia must negotiate in good faith in
the light of the prevailing situation, and must take al1necessary meas-
ures to ensure the achievement of the objectives of the Treaty of
16 September 1977, in accordance with such modalities as they may

agree upon ;
IN FAVOUR P:resident Schwebel; Vice-Prr.sident Weeramantry; Judges
Oda, Bedjaoui, Guillaume, Ranjeva, Shi. Koroma, Vereshchetin,
Parra-Aranguren, Kooijmans, Rezek; Judge ad hoc Skubiszewski;

AGAINST :Judges Herczegh, Fleischhauer ;

C. By thirteen votes to two,
Fin& that, unless the Parties otherwise agree, a joint operational

régimemust be established in accordance with the Treaty of 16 Sep-
tember 1977;
IN FAVOUR : President Schwebel ; Vice-Pre.~identWeeramantry ;Judges
Oda, Bedjaoui, Guillaume, Ranjeva, Shi, Koroma, Vereshchetin,

Parra-Aranguren. Kooijmans, Rezek ;Judge ad hoc Skubiszewski ;

AGAINST :Judges Herczegh, Fleischhauer:

D. By twelve votes to three,

Finds that, unless the Parties otherwise agree, Hungary shall com-
pensate Slovakia for the damage sustained by Czechoslovakia and by
Slovakia on account of the suspension and abandonment by Hun-
gary of works for which it was responsible; and Slovakia shall com-
pensate Hungary for the damage it has sustained on account of the

putting into operation of the "provisional solution" by Czechoslo-
vakia and its maintenance in service by Slovakia;
IN FAVOUR P:resident Schwebel; Vice-Puesident Weeramantry; Judges

Bedjaoui. Guillaume, Ranjeva, Herczegh, Shi, Fleischhauer, Parra-
Aranguren, Kooijmans, Rezek; Judge ad hoc Skubiszewski;
AGAINST J:dges Oda. Koroma, Vereshchetin; PROJET GABCIKOVO-NAGYMA (ARORSÉT) 83

2) Vu le paragraphe 2 de l'artic2eet l'articl5 du compromis,

A. Par douze voix contre trois,

Dit que la Slovaquie, en tant que successeur de la Tchécoslovaquie,
est devenue partie au traité du 16 septembre 1977 à compter du
1" janvier 1993;

POLIR: M. Schwebel, Président; M. Weeramantry, Vice-Pué.vident;
MM. Oda, Bedjaoui,Guillaume, Ranjeva, Shi,Koroma, Vereshchetin,
Parra-Aranguren, Kooijmans,juges; M. Skubiszewski,juge ad hoc;
CONTRE M:M. Herczegh, Fleischhauer, Rezek,uges;

B. Par treize voix contre deux,

Dit que la Hongrie et la Slovaquie doivent négocier de bonne foi en
tenant compte de la situation existanteet doivent prendre toutes
mesures nécessaires à l'effet d'assurer la réalisation des objectifs du

traité du 16 septembre 1977, selon des modalités dont elles convien-
dront;
POL-R: M. Schwebel. Président; M. Weeramantry, Vice-Présiden:t
MM. Oda, Bedjaoui, Guillaume, Ranjeva,Shi. Koroma, Vereshchetin,
Parra-Aranguren, Kooijmanj, Rezek, juges; M. Skubiszewski, juge
ad hoc;

CONTKt :MM. Herczegh, Fleischhauer, juges;

C. Par treize voix contre deux,
Dit que. sauf si les Parties en conviennent autrement, un régime

opérationnel conjoint doit être établi conformément au traité du
16 septembre 1977;
POUR:M. Schwebel, Président; M. Weeramantry, Vice-président;
MM. Oda, Bedjaoui, Guillaume, Ranjeva, Shi,Koroma. Vereshchetin,
Parra-Aranguren, Kooijmans, Rezek, juges; M. Skubiszewski, juge
ad hoc;

CONTRE M:M. Herczegh, Fleisckihauer,juges:

D. Par douze voix contre trois,
Dit que, sauf si les Parties en conviennent autrement, la Hongrie
devra indemniser la Slovaquie pour les dommages subis par la Tché-

coslovaquie et par la Slovaquie du fait de la suspension et de l'aban-
don par la Hongrie de travaux qui lui incombaient; et la Slovaquie
devra indemniser la Hongrie pour les dommages subis par cette der-
nière di1 fait de la mise en service de la ((solution provisoipar la
Tchécoslovaquie et de son maintien en service par la Slovaquie;

POUR:M. Schwebel. Présideizt; M. Weeramantry, Vice-Puc;.~ident;
MM. Bedjaoui,Guillaume, Ranjeva,Herczegh, Shi,Fleischhauer,Parra-
Aranguren, Kooijmans,Rezek,juges; M. Skubiszewski,jugead hoc;
CONTRE M:M. Oda, Koroma. Vereshchetin,juges;84 GABCIKOVO-NAGYM AROOEST(JUDGMENT)

E. By thirteen votes to two,

Finds that the settlement of accounts for tconstruction and
operation of the works must be effected in accordance with the rele-
vant provisions of the Treaty of 16 September 1977 and related
instruments,taking due account of such measures as will have been

taken by the Parties in application of poin2B and 2 C of the
present operative paragraph.
INFAVOUR P:resident Schwebel; Vice-President Weeramantry; Judges
Oda, Bedjaoui, Guillaume, Ranjeva. Shi, Koroma. Vereshchetin,
Parra-Aranguren, Kooijmans, Rezek; Judp ad hoc Skubiszewski;

AGAINST:udges Herczegh, Fleischhauer.

Done in English and in French, the English text being authoritative, at

the Peace Palace, The Hague, this twenty-fifth day of September, one
thousand nine hundred and ninety-seven, in three copies, one of which
will be placed in the archives of the Court and the others transmitted to
the Covernment of the Republic of Hungary and the Government of the
Slovak Republic, respectively.

(Signed) Stephen M. SCHWEBEL,
President.

(Signed) Eduardo VALENCIA-OSPINA,

Registrar.

President SCHWEBEL and Judge REZEKappend declarations to the
Judgment of the Court.

Vice-President WEERAMANTR aYd Judges BEDJAOUIand KOROMA

append separate opinions to the Judgment of the Court.

Judges ODA, RANJEVAH , ERCZEGHF ,LEISCHHAUEV RE, RESHCHETa nd
PARRA-ARANGURE Nd Judge ad hoc SKUBISZEWSa KpIpend dissenting
opinions to the Judgment of the Court.

(Initiullcd) S.M.S.
(Initialled) E.V.O. PROJETGABC~KOVO-NAGYM ARRROÊST) 84

E. Par treize voix contre deux,

Dit que le règlement des comptes concernant la construction et le
fonctionnement des ouvrages doit être effectuéconformément aux dis-
positions pertinentes du traité du 16 septembre 1977 et des instru-

ments y afférents, compte dûment tenu des mesures qui auront été
prises par les Parties en application des points et2 C du présent
dispositif.

POUR: M. Schwebel, Présiderit; M. Weeramantry, Vice-Président ;
MM. Oda, Bedjaoui,Guillauine,Ranjeva, Shi,Koroma, Vereshchetin,
Parra-Aranguren. Kooijmans, Rezek,juges; M. Skubiszewski,juge ad
hoc:
CONTRE:MM. Herczegh, Fleischhauer,juges.

Fait en anglais et en français, le texte anglais faisant foi, au Palais de la
Paix, à La Haye, le vingt-cinq septembre mil neuf cent quatre-vingt-dix-
sept, en trois exemplaires, dont l'{ln restera déposéaux archives de la
Cour et les autres seront transmis respectivement au Gouvernement de la
République de Hongrie et au Gouvernement de la République slovaque.

Le Président,
(Signé) Stephen M. SCHWEBEL.

Le Greffier,

(Signé) Eduardo VALENCIA-OSPINA.

M. SCHWEBEP Lr,ésident,et M. REZEKj,uge, joignent des déclarations à
l'arrêt.

M. WEERAMANTRY V,ice-Président, et MM. BEDJAOUeIt KOROMA,

juges, joignent à l'arrêtles exposésde leur opinion individuelle.

MM. ODA, RANJEVAH , ERCZEGHF , LEISCHHAUER V,ERESHCHETIeN t
PARRA-ARANGURE jNg,es, et M. SKUBISZEWSjK ug,ead hoc, joignent à
l'arrêtles exposésde leur opinion dissidente.

(Paraphé) S.M.S.
(Parapllé) E.V.O.

Document file FR
Document Long Title

Judgment of 25 September 1997

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