Judgment of 12 July 2005

Document Number
125-20050712-JUD-01-00-EN
Document Type
Date of the Document
Document File
Bilingual Document File

COUR INTERNATIONALE DE JUSTICE

RECUEIL DES AR|TS,
AVIS CONSULTATIFS ET ORDONNANCES

AFFAIRE

DU DIFFE uREND FRONTALIER
(BuNIN/NIGER)

ARR|T DU 12 JUILLET 2005

2005

INTERNATIONAL COURT OF JUSTICE

REPORTS OF JUDGMENTS,
ADVISORY OPINIONS AND ORDERS

CASE CONCERNING

THE FRONTIER DISPUTE
(BENIN/NIGER)

JUDGMENT OF 12 JULY 2005 Mode officiel de citation:
Différend frontalier (Bénin/Niger),
arrêt, C.I.J. Recueil 2005 ,p.90

Official citation:
Frontier Dispute (Benin/Niger),
Judgment, I.C.J. Reports 2005 ,p.90

o
N de vente:
ISSN 0074-4441 Sales number 902
ISBN 92-1-071012-6 12 JUILLET 2005

ARRE|T

DIFFuREND FRONTALIER

(BuNIN/NIGER)

FRONTIER DISPUTE

(BENIN/NIGER)

12 JULY 2005

JUDGMENT 90

INTERNATIONAL COURT OF JUSTICE

YEAR 2005 2005
12 July
12 July 2005 General List
No. 125

CASE CONCERNING
THE FRONTIER DISPUTE

(BENIN/NIGER)

Geographical context — Historical background.
Applicable law — Principle of uti possidetis juris — Course of the boundary
to be determined by reference to the physical situation to which French colonial
law was applied, as that situation existed at the dates of independence — Con-
sequences of that course on the ground to be assessed in relation to present-day
physical realities — Relevance of documents and maps posterior to dates of
independence for purposes of applying the uti possidetis juris principle — Legal
value of post-colonial effectivités.

Place of colonial law (French droit d’outre-mer) — Powers of colonial

authorities to create and abolish colonies and territorial subdivisions .

Evolution of legal status of territories concerned .
Principal documents relevant to the settlement of the dispute .
Cartographic materials — Value of maps as evidence.

**

Course of boundary in River Niger sector and the question of to which Party
the islands in the river belong.
Examination of regulative and administrative acts invoked by the Parties .
Arrêté of 23 July 1900 of the Governor-General of French West Africa
(AOF) and decree of 20 December 1900 of the President of the French Repub-
lic did not fix the boundaries of the third military territory — Arrêté of 1900 did
not locate the intercolonial boundary on the left bank of the River Niger — Let-
ter of 27 August 1954 from Mr. Raynier, Governor ad interim of Niger — Con-
text of that letter — Letter cannot be seen as authoritative confirmation of a
previously established boundary — Benin’s contention that the said letter, in
conjunction with the decree of 23 July 1900, constitutes a legal title substanti-
ating its claims cannot be upheld.

4 FRONTIER DISPUTE (JUDGMENT ) 91

Arrêtés of 8 December 1934 and 27 October 1938 of the Governor-General of
the AOF — Did not locate the intercolonial boundary in the river — Niger’s
contention that said arrêtés constitute a legal title substantiating its claims can-
not be upheld.
No evidence of existence of a title determining the boundary in the colonial

period — Legal relationship between title and effectivités.
Consideration of effectivités relied on by the Parties — Effectivités prior to
1954 — Letter from administrateur adjoint Sadoux of 3 July 1914 and modus
vivendi — Terms of modus vivendi generally respected until 1954 — Island of
Lété administered by Niger — Islands opposite Gaya administered by Daho-
mey — Situation less clear between 1954 and critical date — Administration of
island of Lété not transferred to or taken over by Dahomey during this period.

Boundary between the Parties follows the main navigable channel of the River
Niger as it existed at the dates of independence and passes to the left of the
three islands opposite Gaya — Attribution of islands in the river according to
this boundary.

*
Precise location of boundary line in the main navigable channel — Line of
deepest soundings as it existed at the dates of independence.

Hydrographic and topographic surveys of the river over the course of time —
Riverbed relatively stable — NEDECO report of 1970 the most useful source of
information on the situation at the critical date — Boundary between the
Parties follows the line of deepest soundings of the main navigable channel of
the River Niger as it appears in that report and to be constituted opposite Gaya
by the line of deepest soundings of the left navigable channel, except in the vicin-
ity of the island of Kata Goungou, where it passes to the left of that island —
Co-ordinates of the points through which the boundary passes .

Determination of which of the islands in the river belong to Benin and which
to Niger — Determination without prejudice to private law rights in respect of
the islands.

*
Course of the boundary on the bridges between Gaya and Malanville —
Chamber’s jurisdiction to determine that boundary — Boundary on the bridges
to follow the course of the boundary in the river.

**
Course of the boundary in the River Mekrou sector .
Consideration of the documents relied on by the Parties — Decree of 2 March

1907 effected a delimitation in this sector — Decree of 1 March 1919 creating
the colony of Haute-Volta did not implicitly abrogate or amend the decree of
1907 — Arrêté of 31 August 1927 and erratum of 15 October 1927 defining the
boundary between the colonies of Haute-Volta and Niger — Instruments con-
cerning the creation of game reserves and national parks in the “Niger W” area .

Cartographic materials.

5 FRONTIER DISPUTE (JUDGMENT ) 92

Line of 1907 no longer corresponded to the intercolonial boundary at the
critical date — Decree of 1907 was never expressly abrogated or amended or
superseded by another text — Power of the Governor-General of AOF to fix the
boundaries of cercles and, hence, to determine those of colonies where the
boundaries of a cercle are also those of a colony — Uti possidetis juris principle

requires that account be taken of the manner in which titles were interpreted and
applied by the competent public authorities of the colonial Power — River
Mekrou regarded as intercolonial boundary at the critical date .

Boundary between the Parties constituted by the median line of the River
Mekrou.

JUDGMENT

Present: Judge R ANJEVA, Vice-President of the Court, President of the
Chamber; Judges K OOIJMANS,A BRAHAM ; Judges ad hoc B EDJAOUI,

BENNOUNA ; Registrar OUVREUR .

In the case concerning the frontier dispute,

between

the Republic of Benin,
represented by
H.E. Mr. Rogatien Biaou, Minister for Foreign Affairs and African Integra-

tion,
as Agent;

H.E. Mr. Dorothé C. Sossa, Keeper of the Seals, Minister of Justice, Legisla-
tion and Human Rights,
as Co-Agent;

H.E. Mr. Euloge Hinvi, Ambassador of the Republic of Benin to the Benelux
countries,
as Deputy Agent;

Maître Robert Dossou, Avocat at the Benin bar, former Bâtonnier, Honor-
ary Dean of the Law Faculty, University of Abomey-Calavi,
Mr. Alain Pellet, Professor of Law, University of Paris X-Nanterre, member
and former Chairman of the International Law Commission,
Mr. Jean-Marc Thouvenin, Professor of Law, University of Paris X-Nan-
terre, Avocat at the Paris Bar, partner in the Lysias law firm,
Mr. Mathias Forteau, Professor of Law at the University of Lille 2 and at

the Lille Institute of Political Studies,
as Counsel and Advocates;

Mr. Francis Lokossa, Director of Legal Affairs and Human Rights, Ministry
of Foreign Affairs and African Integration,
as Special Adviser;

6 FRONTIER DISPUTE (JUDGMENT ) 93

Mr. François Noudegbessi, Permanent Secretary, National Commission for
the Delimitation of Boundaries,
Mr. Jean-Baptiste Monkotan, Legal Adviser to the President of the Republic
of Benin,
Mr. Honoré D. Koukoui, Secretary General, Ministry of Justice, Legislation

and Human Rights,
Mr. Jacques Migan, Avocat at the Cotonou Bar, Legal Adviser to the Presi-
dent of the Republic of Benin,
Ms Héloïse Bajer-Pellet, Avocat at the Paris Bar, Lysias law firm,
Mr. Luke Vidal, lawyer, Lysias law firm,
Mr. Daniel Müller, lawyer, Researcher at the Centre de droit international
de Nanterre (CEDIN),
Ms Christine Terriat, lawyer, Maître Robert M. Dossou law firm,
Mr. Maxime Jean-Claude Hounyovi, Economist, Maître Robert M. Dossou
law firm,
Mr. Edouard Roko, First Secretary, Embassy of the Republic of Benin to
the Benelux countries,

as Advisers;
Mr. Pascal Lokovi, Cartographer,

Mr. Clément C. Vodouhe, Historian,
as Counsel and Experts;
Ms Collette Tossouko, Secretarial Assistant, Embassy of the Republic of
Benin to the Benelux countries,

as Secretary,
and

the Republic of Niger,
represented by

H.E. Ms Aïchatou Mindaoudou, Minister for Foreign Affairs, Co-operation
and African Integration,
as Agent;

H.E. Mr. Maty El Hadji Moussa, Minister of Justice, Keeper of the Seals,
as Co-Agent;
H.E. Mr. Souley Hassane, Minister of National Defence;
H.E. Mr. Mounkaïla Mody, Minister of the Interior and Decentralization;

Mr. Boukar Ary Maï Tanimoune, Director of Legal Affairs and Litigation,
Ministry of Foreign Affairs, Co-operation and African Integration,

as Deputy Agent, Legal Adviser and Co-ordinator;

Mr. Jean Salmon, Professor Emeritus, Université libre de Bruxelles,
as Lead Counsel;
Mr. Maurice Kamto, Professor, University of Yaoundé II,
Mr. Gérard Niyungeko, Professor and former Vice-Recteur, University of
Burundi, former President of the Constitutional Court of Burundi,

Mr. Amadou Tankoano, Professor, Abdou Moumouni University, Niamey,
Mr. Pierre Klein, Professor, Université libre de Bruxelles,
as Counsel;

7 FRONTIER DISPUTE JUDGMENT ) 94

Mr. Sadé Elhadji Mahamane, Chief Curator of Libraries and Archives,
member of the National Boundaries Commission,
Mr. Amadou Maouli Laminou, Magistrat, Head of Section at the Ministry
of Justice,
H.E. Mr. Abdou Abarry, Ambassador of the Republic of Niger to the King-
dom of the Netherlands,
Mr. Abdelkader Dodo, Hydro-geologist, Lecturer at the Faculty of Sciences,

Abdou Moumouni University, Niamey,
Mr. Belko Garba, Chief Surveyor, member of the National Boundaries
Commission,
Mr. M. Hamadou Mounkaïla, Chief Surveyor, Head of Department, Perma-
nent Secretariat of the National Boundaries Commission,
Mr. Idrissa Y Maïga, Chief Curator of Libraries and Archives, Director of
National Archives, member of the National Boundaries Commission,
Mr. Mahaman Laminou, Director-General of the National Geographical
Institute of Niger, member of the National Boundaries Commission,

Mr. Mahamane Koraou, Permanent Secretary to the National Boundaries
Commission,
Mr. Soumaye Poutia, Magistrat, Technical Adviser to the Office of the Prime
Minister,
Colonel Yayé Garba, Secretary General of the Ministry for National Defence,
Mr. Moutari Laouali, Governor of the Region of Dosso,

as Experts;
Mr. Emmanuel Klimis, Research Assistant at the Centre for International
Law, Université libre de Bruxelles,
Mr. Boureima Diambeïdou, Chief Surveyor,
Mr. Bachir Hamissou, Administrative Assistant,

Mr. Ouba Adamou, Chief Surveyor, National Geographic Institute of
Niger,
as Research Assistants;

Mr. Salissou Mahamane, Accountant,
Mr. Adboulsalam Nouri, Principal Secretary,
Ms Haoua Ibrahim, Secretary,
Mr. Amadou Gagéré, Administrative Officer,
Mr. Amadou Tahirou, Administrative Officer,
Mr. Mamane Chamsou Maïgari, journalist, Director of Voix du Sahel,
Mr. Goussama Saley Madougou, cameraman for national television,
Mr. Ali Moussa, journalist with the Niger Press Agency,

Mr. Issoufou Guéro, journalist,
as Administrative and Technical Staff,

T HE CHAMBER OF THE INTERNATIONAL C OURT OF JUSTICEformed to deal with
the above-mentioned case,

composed as above,

after deliberation,
delivers the following Judgment:

1. By a joint letter of notification dated 11 April 2002, filed in the Registry of
the Court on 3 May 2002, the Republic of Benin (hereinafter “Benin”) and the

8 FRONTIER DISPUTE (JUDGMENT ) 95

Republic of Niger (hereinafter “Niger”) transmitted to the Registrar a certified
copy of a Special Agreement, which was signed on 15 June 2001 in Cotonou
and entered into force on 11 April 2002, whereby the Governments of the two
States agreed to submit to a Chamber of the Court a dispute concerning “the
definitive delimitation of the whole boundary between them”.

2. The Special Agreement of 15 June 2001 provides as follows:
“The Government of the Republic of Benin and the Government of the
Republic of Niger, hereinafter the ‘Parties’;

Whereas, pursuant to the Agreement signed on 8 April 1994, having
provisionally entered into force on the date of its signing, having been rati-
fied by Benin on 17 July 1997 and by Niger on 1 February 2001, and
having definitively entered into force on 15 June 2001, the date on which
the instruments of ratification were exchanged, the two Governments
created the Joint Delimitation Commission for their boundary;
Whereas, notwithstanding six negotiating sessions held by that Commis-
sion, the two States’ experts have been unable to agree on the course of the

joint boundary;
Whereas, under Article 15 of that Agreement of 8 April 1994,
‘the contracting Parties agree to submit all disputes or disagreements
arising out of the application or interpretation of this Agreement to
settlement through diplomatic channels or by the other means of

peaceful settlement provided for by the Charters of the Organization of
African Unity and the United Nations’;
Desiring to achieve as rapidly as possible the settlement of the boundary
dispute between them on the basis of the provisions of the Charter and the
resolutions of the Organization of African Unity and to submit the ques-
tion of the definitive delimitation of the whole boundary between them to
the International Court of Justice, hereinafter the ‘Court’;

Have agreed as follows:
Article 1
Formation of a Chamber of the International Court of Justice

1. The Parties submit the dispute defined in Article 2 below to a cham-
ber of the Court, hereinafter the ‘Chamber’, formed in accordance with the
provisions of the Statute of the Court and the present Special Agreement.
2. Each of the Parties shall exercise the right granted it by Article 31,
paragraph 3, of the Statute of the Court to proceed to choose a judge
ad hoc.

Article 2
Subject of the Dispute
The Court is requested to:

(a) determine the course of the boundary between the Republic of Benin
and the Republic of Niger in the River Niger sector;
(b) specify which State owns each of the islands in the said river, and in
particular Lété Island;
(c) determine the course of the boundary between the two States in the
River Mekrou sector.

9 FRONTIER DISPUTE (JUDGMENT ) 96

Article 3
Written Proceedings

1. Without prejudice to any question as to the burden of proof, the
Parties request the Chamber to authorize the following procedure for the
written pleadings:
(a) a Memorial filed by each Party not later than nine (9) months after
the adoption by the Court of the Order constituting the Chamber;
(b) a Counter-Memorial filed by each Party not later than nine (9)

months after exchange of the Memorials;
(c) any other pleading whose filing, at the request of either of the Parties,
shall have been authorized or directed by the Court.

2. Pleadings submitted to the Registrar shall not be transmitted to the
other Party until the Registrar has received the corresponding pleading
from that Party.

Article 4
Oral Proceedings
The Parties shall agree, with approval from the Chamber, on the order
in which they are to be heard during the oral proceedings; if the Parties

fail to agree, the order shall be prescribed by the Chamber.

Article 5
Language of the Proceedings

The Parties agree that their written pleadings and their oral argument
shall be presented in the French language.
Article 6
Applicable Law

The rules and principles of international law applicable to the dispute
are those set out in Article 38, paragraph 1, of the Statute of the Interna-
tional Court of Justice, including the principle of State succession to the
boundaries inherited from colonization, that is to say, the intangibility of
those boundaries.

Article 7
Judgment of the Chamber
1. The Parties accept the judgment of the Chamber given pursuant to
the present Special Agreement as final and binding upon them.

2. From the day on which the judgment is rendered, the Parties shall

have eighteen (18) months in which to commence the works of demarca-
tion of the boundary.
3. In case of difficulty in the implementation of the judgment, either
Party may seise the Court pursuant to Article 60 of its Statute.
Article 8
Entry into Force

The present Agreement is subject to ratification. It shall enter into force
on the date on which the instruments of ratification are exchanged, which
shall take place as rapidly as possible.

10 FRONTIER DISPUTE (JUDGMENT ) 97

Article 9
Registration and Notification

The present Agreement shall be registered with the Secretariat of the
United Nations pursuant to Article 102 of the United Nations Charter by
the more diligent Party.
1. In accordance with Article 40 of the Statute of the Court, the present
Special Agreement shall be notified to the Registrar of the Court by a joint
letter from the Parties.
2. If such notification is not effected in accordance with the preceding
paragraph within one month from the entry into force of the present
Special Agreement, it shall be notified to the Registrar of the Court by

the more diligent Party.
Article 10

Special Undertaking
Pending the judgment of the Chamber, the Parties undertake to preserve
peace, security and quiet among the peoples of the two States.

In witness whereof, the present Special Agreement, drawn up in two
original copies, has been signed by the plenipotentiaries.
Done at Cotonou, 15 June 2001.”

3. Pursuant to Article 40, paragraph 3, of the Statute of the Court and
Article 42 of the Rules of Court, the Registrar transmitted copies of the
joint letter of notification, of the Special Agreement and of the protocol of
exchange of the instruments of ratification to the Secretary-General of the
United Nations, the Members of the United Nations and other States entitled
to appear before the Court.
4. Article 1 of the Special Agreement provides for the submission of the dis-
pute to a Chamber to be formed in accordance with Article 26, paragraph 2,
of the Statute, with a judge ad hoc to be chosen by each Party pursuant to
Article 31 of the Statute. The Parties, having been duly consulted by the Presi-

dent of the Court regarding the composition of the Chamber, expressed their
wish, pursuant to Article 26, paragraph 2, of the Statute, and to Article 17,
paragraph 2, of the Rules of Court, for the formation of a Chamber of five
members, of whom two would be the judges ad hoc to be chosen by them.
5. By a letter of 21 August 2002 the Deputy Agent of Benin informed the
Court that his Government had chosen Mr. Mohamed Bennouna to sit as
judge ad hoc. By a letter of 11 September 2002 the Agent of Niger informed the
Court that his Government had chosen Mr. Mohammed Bedjaoui to sit as
judge ad hoc.
6. By an Order of 27 November 2002 the Court, acting pursuant to
Article 26, paragraph 2, of the Statute and Article 17 of the Rules of Court,
decided to accede to the request of the Parties that a special Chamber be formed
to deal with the case; it declared that, at an election held on 27 November 2002,

President Guillaume and Judges Ranjeva and Kooijmans had been elected
to form, together with the above-named judges ad hoc, a Chamber to deal with
the case and that accordingly the said Chamber as so composed had been
duly constituted pursuant to that Order. In accordance with Article 18,
paragraph 2, of the Rules of Court, Judge Guillaume, who held the office of
President of the Court when the Chamber was formed, was to preside over
the Chamber.

11 FRONTIER DISPUTE JUDGMENT ) 98

7. By the same Order, the Court, acting pursuant to Article 92, paragraph 1,
of the Rules of Court, fixed 27 August 2003 as the time-limit for the filing of a
Memorial by each Party and reserved the subsequent procedure for further
decision. The Memorials were duly filed within the time-limit thus fixed.
8. By Order of 11 September 2003, the President of the Chamber, having

regard to Article 3, paragraph 1 (b), of the Special Agreement, fixed 28 May
2004 as the time-limit for the filing of a Counter-Memorial by each Party and
reserved the subsequent procedure for further decision.
9. The Chamber held a public sitting on 20 November 2003 to enable the
judges ad hoc to make the solemn declaration required by Article 31, para-
graph 6, of the Statute and by Article 8 of the Rules of Court.
10. On 28 May 2004, within the time-limit fixed by the Order of 11 Septem-
ber 2003, the Parties filed their respective Counter-Memorials in the Registry.
During a meeting held by the President of the Chamber with the representatives
of the Parties on 2 July 2004, in order to ascertain their views on the subsequent
procedure, the two Parties expressed the wish to be authorized to submit a
third pleading. By Order of 9 July 2004, the President of the Chamber, having
regard to Article 3, paragraph 1 (c), of the Special Agreement, authorized the

filing of a Reply by each Party and fixed 17 December 2004 as the time-limit
therefor, reserving the subsequent procedure for further decision. The Parties
filed their Replies in the Registry within the time-limit thus fixed.

11. By a letter of 11 October 2004, Judge Guillaume, President of the Cham-
ber, informed the President of the Court, pursuant to Article 13, paragraph 4,
of the Statute, that he had decided to resign from the Court with effect from
11 February 2005. Since his resignation would leave a vacancy in the Chamber,
the President of the Court consulted the Parties again on 11 January 2005
regarding the composition of the Chamber. At an election held on 16 February
2005, Judge Abraham was elected a member of the Chamber to fill the seat left
vacant by Judge Guillaume’s resignation. By an Order of 16 February 2005, the
Court declared that, as a result of this election, the Chamber was now com-
posed as follows: Judge Ranjeva, who, in his capacity as Vice-President of the

Court, had become President of the Chamber, pursuant to Article 18, para-
graph 2, of the Rules of Court; Judges Kooijmans and Abraham; and Judges
ad hoc Bedjaoui and Bennouna.
12. By a letter of 11 February 2005, the Agent of Niger expressed his Gov-
ernment’s wish to produce two new documents pursuant to Article 56 of the
Rules of Court. By a letter of 25 February 2005, the Agent of Benin informed
the Chamber that his Government did not object to that production. Following
the decision of the Chamber to authorize the production of those documents
by Niger, the Registrar advised the Parties of that decision by letters dated
2 March 2005.
13. Pursuant to Article 53, paragraph 2, of the Rules of Court, the Chamber,
having ascertained the views of the Parties, decided to make accessible to
the public, with effect from the opening of the oral proceedings, copies of the

written pleadings and of the documents annexed thereto.
14. Public sittings were held on 7, 8, 10 and 11 March 2005, at which the
Chamber heard the oral arguments and replies of:

For Benin: H.E. Mr. Rogatien Biaou,
Mr. Alain Pellet,
Maître Robert Dossou,

12 FRONTIER DISPUTE (JUDGMENT ) 99

Mr. Mathias Forteau,
Mr. Jean-Marc Thouvenin.

For Niger: H.E. Ms Aïchatou Mindaoudou,
Mr. Jean Salmon,
Mr. Amadou Tankoano,
Mr. Gérard Niyungeko,
Mr. Pierre Klein.
At the hearings questions were put by the Chamber, to which replies were

given in writing pursuant to Article 61, paragraph 4, of the Rules of Court.
Each Party submitted its written comments on the other’s written replies in
accordance with Article 72 of the Rules of Court.

*

15. In the course of the written proceedings, the following submissions were
presented by the Parties:
On behalf of the Government of Benin,

in the Memorial:
“Having regard to all of the foregoing considerations, the Republic of
Benin requests the Chamber of the International Court of Justice to
decide:

(1) that the boundary between the Republic of Benin and the Republic of
Niger takes the following course:
— from the point having co-ordinates 11°54′15″ latitude North and
2°25′10″ longitude East, it follows the median line of the River
Mekrou as far as its point of confluence with the River Niger,
— from that point, the boundary continues as far as the left bank of
the River [Niger], which it follows until it reaches the boundary of
Nigeria, as defined by the Franco-British Agreements of 29 May

and 19 October 1906;
(2) that sovereignty over all of the islands in the River [Niger], and in par-
ticular the island of Lété, lies with the Republic of Benin.”

in the Counter-Memorial:
“For the reasons set out in its Memorial and in the present Counter-
Memorial, the Republic of Benin maintains its submissions and requests
the Chamber of the International Court of Justice to decide:

(1) that the boundary between the Republic of Benin and the Republic of
Niger takes the following course:
— from the point having co-ordinates 11°54′15″ latitude North and
2°25′10″ longitude East, it follows the median line of the River
Mekrou as far as the point having co-ordinates 12°24′29″ latitude
North and 2°49′38″ longitude East,
— from that point, the boundary follows the left bank of the River
[Niger] as far as the point having co-ordinates 11°41′44″ North

and 3°36′44″ East;
(2) that sovereignty over all of the islands in the River [Niger], and in par-
ticular the island of Lété, lies with the Republic of Benin.”

13 FRONTIER DISPUTE (JUDGMENT ) 100

in the Reply:

“For the reasons set out in its Memorial and in its Counter-Memorial,
as well as in the present Reply, the Republic of Benin maintains its sub-
missions and requests the Chamber of the International Court of Justice to
decide:
(1) that the boundary between the Republic of Benin and the Republic of
Niger takes the following course:

— from the point having co-ordinates 11°54′15″ latitude North and
2°25′10″ longitude East, it follows the median line of the River
Mekrou as far as the point having co-ordinates 12°24′29″ latitude
North and 2°49′38″ longitude East,
— from that point, the boundary follows the left bank of the River
[Niger] as far as the point having co-ordinates 11°41′44″ North
and 3°36′44″ East;

(2) that sovereignty over all of the islands in the River [Niger], and in par-
ticular the island of Lété, lies with the Republic of Benin.”
On behalf of the Government of Niger,

in the Memorial:
“The Republic of Niger requests the Court to adjudge and declare that:

— the boundary between the Republic of Benin and the Republic of
Niger in the River Niger sector, from the confluence of the River
Mekrou with the River Niger as far as the boundary of Nigeria, fol-
lows the line of deepest soundings, on the understanding that, in the
event of a future change in the course of that line, the boundary
between the Republic of Benin and the Republic of Niger will follow
that new course;
— the current line of deepest soundings in this part of the river deter-
mines which islands belong to each Party;
— the islands located between the line of deepest soundings and the right
bank of the river, namely Tondi Kwaria Barou, Koki Barou, Sandi
Tounga Barou, Gandégabi Barou Kaïna, Dan Koré Guirawa, Barou
Elhadji Dan Djoda, Koundou Barou, Elhadji Chaïbou Barou Kaïna

and Dolé Barou, belong to the Republic of Benin;
— the islands located between the line of deepest soundings and the left
bank of the river, namely Boumba Barou Béri, Boumba Barou Kaïna,
Kouassi Barou, Sansan Goungou, Lété Goungou, Monboye Tounga
Barou, Sini Goungou, Lama Barou, Kotcha Barou, Gagno Goungou,
Kata Goungou, Gandégabi Barou Béri, Guirawa Barou, Elhadji
Chaïbou Barou Béri, Goussou Barou and Beyo Barou, belong to the
Republic of Niger;
— the attribution of islands to the Republic of Benin and the Republic of
Niger shall be regarded as final, even in the event of a future change in
the course of the line of deepest soundings;
— the boundary between the Republic of Benin and the Republic of
Niger in the River Mekrou sector follows a line comprising two parts:

— the first part is a straight line joining the point of confluence of the
River Mekrou with the River Niger to the point where the Paris
meridian meets the Atacora mountain range, indicative co-ordi-

14 FRONTIER DISPUTE (JUDGMENT ) 101

nates of which are as follows: latitude: 11°41′50″ North; longi-
tude: 2°20′14″ East;
— the second part of the line joins this latter point to the point where
the former boundary between the cercles of Say and Fada meets
the former boundary between the cercles of Fada and Atacora,

indicative co-ordinates of which are as follows: latitude: 11°44′37″
North; longitude: 2°18′55″ East.”
in the Counter-Memorial:

“The Republic of Niger requests the Court to adjudge and declare that:
— the boundary between the Republic of Benin and the Republic of
Niger in the River Niger sector, from the confluence of the River
Mekrou with the River Niger as far as the boundary of Nigeria, fol-
lows the line of deepest soundings, on the understanding that, in the

event of a future change in the course of that line, the boundary
between the Republic of Benin and the Republic of Niger will follow
that new course;
— the current course of the line of deepest soundings in this part of the
river determines which islands belong to each Party;
— the islands located between the line of deepest soundings and the right
bank of the river, namely Tondi Kwaria Barou, Koki Barou, Sandi
Tounga Barou, Gandégabi Barou Kaïna, Dan Koré Guirawa, Barou
Elhadji Dan Djoda, Koundou Barou, Elhadji Chaïbou Barou Kaïna
and Dolé Barou, belong to the Republic of Benin;
— the islands located between the line of deepest soundings and the left
bank of the river, namely Boumba Barou Béri, Boumba Barou Kaïna,
Kouassi Barou, Sansan Goungou, Lété Goungou, Monboye Tounga

Barou, Sini Goungou, Lama Barou, Kotcha Barou, Gagno Goungou,
Kata Goungou, Gandégabi Barou Béri, Guirawa Barou, Elhadji
Chaïbou Barou Béri, Goussou Barou and Beyo Barou, belong to the
Republic of Niger;
— the attribution of islands to the Republic of Benin and the Republic of
Niger shall be regarded as final, even in the event of a future change in
the course of the line of deepest soundings;
— the boundary between the Republic of Benin and the Republic of
Niger in the River Mekrou sector follows a line comprising two parts:

— the first part is a straight line joining the point of confluence of the
River Mekrou with the River Niger to the point where the Paris
meridian meets the Atacora mountain range, indicative co-ordi-
nates of which are as follows: latitude: 11°41′50″ North; longi-
tude: 2°20′14″ East;
— the second part of the line joins this latter point to the point where
the former boundary between the cercles of Say and Fada meets
the former boundary between the cercles of Fada and Atacora,
indicative co-ordinates of which are as follows: latitude: 11°44′37″
North; longitude: 2°18′55″ East.”

in the Reply:
“The Republic of Niger requests the Court to adjudge and declare that:

— the boundary between the Republic of Benin and the Republic of
Niger in the River Niger sector, from the confluence of the River

15 FRONTIER DISPUTE (JUDGMENT ) 102

Mekrou with the River Niger as far as the boundary of Nigeria, fol-
lows the line of deepest soundings, in so far as that line can be estab-
lished as it was at the date of independence;
— that line determines which islands belong to each Party;

— the islands between the line of deepest soundings and the right bank of
the river, namely Pekinga, Tondi Kwaria Barou, Koki Barou, Sandi
Tounga Barou, Gandégabi Barou Kaïna, Dan Koré Guirawa, Barou
Elhadji Dan Djoda, Koundou Barou and Elhadji Chaïbou Barou
Kaïna, belong to the Republic of Benin;
— the islands located between the line of deepest soundings and the left
bank of the river, namely Boumba Barou Béri, Boumba Barou Kaïna,
Kouassi Barou, Sansan Goungou, Lété Goungou, Monboye Tounga
Barou, Sini Goungou, Lama Barou, Kotcha Barou, Gagno Goungou,
Kata Goungou, Gandégabi Barou Béri, Guirawa Barou, Elhadji
Chaïbou Barou Béri, Goussou Barou, Beyo Barou and Dolé Barou,
belong to the Republic of Niger;
— the attribution of islands to the Republic of Benin and the Republic of

Niger according to the line of deepest soundings as determined at the
date of independence shall be regarded as final. It shall be for the
Parties to ensure that this channel remains the principal navigable
channel by carrying out dredging works as necessary;
— the boundary between the Republic of Benin and the Republic of
Niger in the River Mekrou sector follows a line comprising two parts:
— the first part is a straight line joining the point of confluence of the
River Mekrou with the River Niger to the point where the Paris

meridian meets the Atacora mountain range, indicative co-ordi-
nates of which are as follows: latitude: 11°41′50″ North; longi-
tude: 2°20′14″ East;
— the second part of the line joins this latter point to the point where
the former boundary between the cercles of Say and Fada meets
the former boundary between the cercles of Fada and Atacora,
indicative co-ordinates of which are as follows: latitude: 11°44′37″
North; longitude: 2°18′55″ East.”

16. At the oral proceedings, the following submissions were presented by the
Parties:

On behalf of the Government of Benin,
“For the reasons set out in its written and oral pleadings, the Republic
of Benin requests the Chamber of the International Court of Justice to

decide:
(1) that the boundary between the Republic of Benin and the Republic of
Niger takes the following course:

— from the point having co-ordinates 11°54′15″ latitude North and
2°25′10″ longitude East, it follows the median line of the River
Mekrou as far as the point having co-ordinates 12°24′29″ latitude
North and 2°49′38″ longitude East,
— from that point, the boundary follows the left bank of the River
[Niger] as far as the point having co-ordinates 11°41′44″ North
and 3°36′44″ East;

16 FRONTIER DISPUTE JUDGMENT ) 103

(2) that sovereignty over all of the islands in the River [Niger], and in par-
ticular the island of Lété, lies with the Republic of Benin.”

On behalf of the Government of Niger,
“The Republic of Niger requests the Court to adjudge and declare that:

(1) The boundary between the Republic of Benin and the Republic of
Niger follows the line of deepest soundings in the River Niger, in so
far as that line could be established at the date of independence, from
the point having co-ordinates latitude 12°24′27″ North, longitude
2°49′36″ East, as far as the point having co-ordinates latitude
11°41′40.7″ North, longitude 3°36′44″ East.
(2) That line determines which islands belong to each Party.

— The islands between the line of deepest soundings and the right
bank of the river, namely Pekinga, Tondi Kwaria Barou, Koki
Barou, Sandi Tounga Barou, Gandégabi Barou Kaïna, Dan Koré
Guirawa, Barou Elhadji Dan Djoda, Koundou Barou and Elhadji
Chaïbou Barou Kaïna, belong to the Republic of Benin.
— The islands located between the line of deepest soundings and the
left bank of the river, namely Boumba Barou Béri, Boumba Barou
Kaïna, Kouassi Barou, Sansan Goungou, Lété Goungou, Mon-
boye Tounga Barou, Sini Goungou, Lama Barou, Kotcha Barou,
Gagno Goungou, Kata Goungou, Gandégabi Barou Béri, Guirawa
Barou, Elhadji Chaïbou Barou Béri, Goussou Barou, Beyo Barou
and Dolé Barou, belong to the Republic of Niger.

(3) The attribution of islands to the Republic of Benin and the Republic
of Niger according to the line of deepest soundings as determined at
the date of independence shall be regarded as final.
(4) With regard to the Gaya-Malanville bridges, the boundary passes
through the middle of each of those structures.
(5) The boundary between the Republic of Benin and the Republic of
Niger in the River Mekrou sector follows a line comprising two parts:

— the first part is a straight line joining the point of confluence of the
River Mekrou with the River Niger to the point where the Paris
meridian meets the Atacora mountain range, indicative co-ordi-
nates of which are as follows: latitude: 11°41′50″ North; longi-
tude: 2°20′14″ East;
— the second part of the line joins this latter point to the point where
the former boundary between the cercles of Say and Fada meets
the former boundary between the cercles of Fada and Atacora,
indicative co-ordinates of which are as follows: latitude: 11°44′37″
North; longitude: 2°18′55″ East.”

*
* *
17. The task assigned to the Chamber in the present case by the
Special Agreement of 15 June 2001 is to determine the course of the

whole boundary between Benin and Niger and to specify to which State
each of the islands in the River Niger sector belongs, and in particular
the island of Lété.

17 FRONTIER DISPUTE (JUDGMENT ) 104

Benin and Niger are States in western Africa. The Republic of Benin,
formerly known as the Republic of Dahomey (from 1960 to 1975) then as

the People’s Republic of Benin (from 1975 to 1990), covers an area of
112,622 sq km; it is bounded to the south by the Atlantic Ocean, to the
west by Togo, to the north-west by Burkina Faso, to the north by Niger
and to the east by Nigeria. The Republic of Niger, with an area of
1,267,000 sq km, is bounded to the south by Nigeria, to the south-west by

Benin, to the west by Burkina Faso, to the north-west by Mali, to the
north by Libya and Algeria, and to the east by Chad. Sketch-map No. 1,
on page 105 below, illustrates the general situation of the territories of
the Parties.
18. Article 2 of the Special Agreement divides the disputed boundary

into two sectors: the River Mekrou sector in the west and the River
Niger sector in the east. Sketch-map No. 2, on page 106 below, gives a
general view of this boundary.
The western part of this boundary follows a course running approxi-
mately south-west to north-east, passing through woodland composed of
transitional Sudano-Sahelian vegetation, from a point marking the

boundary between the two States and Burkina Faso as far as the conflu-
ence of the River Mekrou and the River Niger.
The eastern part of the boundary follows the River Niger in a south-
easterly direction over a distance of some 150 km from that confluence
and ends at a point marking the boundary of the two States with Nigeria.

The Parties have submitted differing descriptions of the characteristics of
the River Niger in the region. According to Benin, the river is subject to
siltation, which has led to a change in its course over time particularly
affecting the right bank, which is much less stable than the left bank.
Although it acknowledges the existence of this phenomenon, Niger main-

tains that, because of the nature of the rocks in the stretch of river con-
cerned, there has been no significant change in the course of the main
channel for more than a century, and that there is no substantial differ-
ence in the configuration of each bank. In this sector, three tributaries
(the Mekrou, the Alibori and the Sota) enter the River Niger from the

right bank, as a result of which it floods twice a year, in January-March
and in September-October. The Parties have conflicting views as to
whether, in the area subject to delimitation, the river is navigable during
the low-water season: Benin claims that it is not but Niger maintains that
navigation is possible throughout the year for certain types of craft.

19. There are several islands within the stretch concerned; their exact
number and their attribution to either Party are matters of dispute in the
present case.
The island of Lété, referred to expressly in Article 2 (b) of the Special
Agreement, is the largest, covering approximately 40 sq km. It extends

16,300 m from a point opposite the villages of Kwara Tegui (Benin) and
Ouna (Niger) to a point opposite the villages of Karimama (Benin) and
Albarkaizé (Niger). The approximate co-ordinates of the extremities of

18FRONTIER DISPUTE (JUDGMENT ) 105

19FRONTIER DISPUTE (JUDGMENT ) 106 FRONTIER DISPUTE (JUDGMENT ) 107

the island are: upstream, 12°9′55″ latitude North and 3°6′47″ longitude
East; downstream, 12°3′43″ latitude North and 3°13′39″ longitude East.

The island is fertile, with rich pastures, and is permanently inhabited;
according to information supplied by Niger, its population numbered
some 2,000 in the year 2000.

**

20. The frontier dispute between the Parties is set within a historical
context marked by the accession to independence of the territories that
were formerly part of French West Africa (“Afrique occidentale

française”, hereinafter “AOF”). Benin, which has been independent since
1 August 1960, corresponds to the former colony of Dahomey, and
Niger, which has been independent since 3 August 1960, corresponds to a
territory which underwent various administrative transformations during
the colonial period.
21. In their written pleadings, both Parties referred to incidents that

occurred on the island of Lété on the eve of their independence, in 1959
and 1960. Following those events, the two States set up a process for the
friendly settlement of their frontier dispute: in 1961 and 1963 two Daho-
mey-Niger joint commissions met to discuss the matter.

In October 1963 the crisis between Dahomey and Niger deepened, in
particular regarding the island of Lété. Each State subsequently pub-
lished a White Paper setting out, inter alia, their respective positions
regarding the frontier dispute.
There were fresh attempts to reach a peaceful settlement in the years

that followed, culminating in a conference held in Yamoussoukro on
18 January 1965, in the course of which the Parties agreed “until the dis-
pute over the island is finally settled, to allow nationals of both countries
to live in perfect harmony on that island”. However, the issue of sover-
eignty over the island of Lété was not resolved and there were further

incidents in subsequent years, notably in 1993 and 1998.
22. On 8 April 1994 Benin and Niger entered into an agreement
creating a joint commission for the delimitation of their common
border, whose terms of reference included the enumeration, collection
and analysis of documents relating to the frontier and the precise
establishment thereof. The commission held six meetings between Sep-

tember 1995 and June 2000.
Since efforts to arrive at a negotiated solution to the dispute were
unsuccessful, the commission proposed that the Governments of the
two States bring the dispute before the International Court of Justice
by Special Agreement. The Special Agreement was signed in Cotonou on

15 June 2001 and entered into force on 11 April 2002.

**

21 FRONTIER DISPUTE JUDGMENT ) 108

23. Under Article 6 of the Special Agreement (“Applicable Law”), the
rules and principles of international law applicable to the present dispute

include “the principle of State succession to the boundaries inherited
from colonization, that is to say, the intangibility of those boundaries”. It
follows from the wording of this provision and from the arguments of the
Parties that they are in agreement on the relevance of the principle of uti
possidetis juris for the purposes of determining their common border. As

the Chamber formed in the case concerning the Frontier Dispute (Burkina
Faso/Republic of Mali) had occasion to state, the existence of this prin-
ciple has been recognized on several occasions in the African context
(Frontier Dispute (Burkina Faso/Republic of Mali), Judgment, I.C.J.
Reports 1986, p. 565, para. 20); it was recognized again recently, in

Article 4 (b) of the Constitutive Act of the African Union, of which
Benin and Niger are members, signed in Lomé on 11 July 2000. That
Chamber stated that, according to the principle in question, “pre-
eminence [is] accorded to legal title over effective possession as a basis
of sovereignty” and that its essence lies “in its primary aim of securing
respect for the territorial boundaries at the moment when independence

is achieved”, including former administrative delimitations established
during the colonial period that became international frontiers (I.C.J.
Reports 1986, pp. 586-587, para. 63, and p. 566, para. 23).
24. On the basis of the principle of uti possidetis juris, the present
Chamber must thus seek to determine, in the case before it, the boundary

that was inherited from the French administration. The Parties agree that
the dates to be taken into account for this purpose are those of their
respective independence, namely 1 and 3 August 1960; the Chamber
would observe that there was no change in the frontier between these two
very close dates.

25. The Parties have nonetheless sometimes expressed differing
opinions regarding certain aspects of the application of the uti possidetis
juris principle in the present case.
Firstly, Niger maintains that this principle does not preclude the Cham-

ber from taking account, where appropriate, of the physical realities sub-
sequent to independence, in order to ensure that the Judgment will have
meaningful and practical significance between the Parties. Consequently,
in requesting the Chamber to indicate to which State each of the islands
in the River Niger belongs, by reference to the line of deepest soundings
at the date of independence, Niger asks it to consider for this purpose

only those islands that exist at the present time.
Benin, for its part, argues that, if the uti possidetis juris principle is to
be applied strictly, it would be unacceptable to refer to the present situa-
tion in order to determine to which Party the islands belonged at the date
of independence.

The Chamber observes that, in any event, the Parties agree that the
course of their common boundary should be determined, in accordance
with the uti possidetis juris principle, by reference to the physical situa-

22 FRONTIER DISPUTE (JUDGMENT ) 109

tion to which French colonial law was applied, as that situation existed at
the dates of independence. However, the consequences of such a course

on the ground, particularly with regard to the question of to which Party
the islands in the River Niger belong, must be assessed in relation to
present-day physical realities and, in carrying out the task assigned to it
under Article 2 of the Special Agreement, the Chamber cannot disregard
the possible appearance or disappearance of certain islands in the stretch

concerned.
26. Secondly, Benin and Niger have put forward differing views with
respect to the documents or maps on which the Chamber should base its
determination of their common boundary.
In support of its delimitation claims, Niger relies on certain documents

and maps that are posterior to the dates of independence, not only to
demonstrate current physical realities but also to establish the situation
existing in the colonial era. According to Niger, that situation must be
determined on the basis of the studies conducted closest in time to the
Parties’ accession to independence, without being confined to those con-
ducted prior to the dates of independence.

Benin considers, to the contrary, that the Chamber should base its
decision on research and documents prior to the critical date.
The Chamber cannot exclude a priori the possibility that maps, research
or other documents subsequent to that date may be relevant in order to

establish, in application of the uti possidetis juris principle, the situation
that existed at the time. In any event, since the effect of the uti possidetis
principle is to freeze the territorial title (Frontier Dispute (Burkina Faso/
Republic of Mali), Judgment, I.C.J. Reports 1986 , p. 568, para. 29), the
examination of documents posterior to independence cannot lead to any

modification of the “photograph of the territory” at the critical date
unless, of course, such documents clearly express the Parties’ agreement
to such a change.
27. Thirdly, the Parties have discussed the legal value, in the light of
the uti possidetis juris principle, of post-colonial effectivités.

The Chamber notes that both Parties have on occasion sought to con-
firm the legal title which they claim by relying on acts whereby their
authorities allegedly exercised sovereignty over the disputed territories
after 1960; such effectivités have been invoked by Niger inter alia in
respect of activities relating to the River Niger and its islands, and by
Benin in respect of activities relating to the right bank of the River

Mekrou.
Such an approach should not necessarily be excluded. As stated by the
Chamber formed in the case concerning the Land, Island and Maritime
Frontier Dispute (El Salvador/Honduras: Nicaragua intervening) ,tisi
possible to

“have regard . . . in certain instances, to documentary evidence of
post-independence effectivités w en..hyardiosni

23 FRONTIER DISPUTE JUDGMENT ) 110

respect of the . . . uti possidetis juris boundary, providing a relation-
ship exists between the effectivités concerned and the determination

of that boundary” (Judgment, I.C.J. Reports 1992, p. 399, para. 62).

*

28. The Parties both acknowledge that, in accordance with the prin-
ciple of uti possidetis juris, the course of the frontier and the attribution
of islands in the River Niger to either one of them must be determined in
the light of French colonial law, known as “droit d’outre-mer”. They
also agree on the identification of the relevant rules of that law, but do

not share the same interpretation thereof.
Before turning to those rules, the Chamber would recall that, when ref-
erence is made to domestic law in such a context, that law is applicable

“not in itself (as if there were a sort of continuum juris, a legal relay
between such law and international law), but only as one factual ele-
ment among others, or as evidence indicative of . . . the ‘colonial
heritage’ ” (Frontier Dispute (Burkina Faso/Republic of Mali), Judg-
ment, I.C.J. Reports 1986 , p. 568, para. 30).

29. As the Chamber in the case concerning the Frontier Dispute

(Burkina Faso/Republic of Mali) (I.C.J. Reports 1986, pp. 568-569,
para. 31) already observed, the territorial administration of the French
possessions in West Africa was centralized by a decree of the President of
the French Republic of 16 June 1895 and placed under the authority of a
Governor-General. The entity of the AOF thus created was divided into

colonies, headed by Lieutenant-Governors and themselves made up of
basic units called “cercles” which were administered by commandants de
cercle; each cercle was in turn composed of subdivisions, each adminis-
tered by a chef de subdivision. The subdivisions consisted of cantons,
which grouped together a number of villages.

30. The Parties acknowledge that the creation and abolition of colo-
nies fell within the jurisdiction of the authorities of metropolitan France:
the President of the French Republic, acting by decree, under the Con-
stitution of the Third Republic, and subsequently the French Parliament,
following the adoption of the Constitution of 27 October 1946.
The power to create territorial subdivisions within a single colony, on

the other hand, was vested in the AOF until being transferred to the local
representative institutions in 1957.
Article 5 of the decree of the President of the French Republic, dated
18 October 1904, providing for the reorganization of the AOF, vested the
Governor-General with authority to “determine in government council

(conseil de gouvernement) , and on the proposal of the Lieutenant-Gov-
ernors concerned, the administrative districts in each of the colonies”.
In his circular No. 114c of 3 November 1912, concerning the form of

24 FRONTIER DISPUTE (JUDGMENT ) 111

instruments for the organization of administrative districts and subdivi-
sions, the Governor-General interpreted this text as conferring upon him

“the right to establish . . . the number and extent of the cercles which,
within the colonies, constitute[d] the actual administrative unit”, but
pointed out that it was “acknowledged that the Lieutenant-Governors
would retain the power to determine the territorial subdivisions created
within these cercles by measures adopted under their own authority”.

According to that circular, “any measure concerning the administrative
district, the territorial unit proper, i.e. affecting the cercle, in terms of its
existence (creation or abolition), its extent, its name, or the location of its
administrative centre”, was to be confirmed by an arrêté général adopted
in government council; it lay with the Lieutenant-Governors “to define,

by means of arrêtés, the approval of which [was] reserved to [the Gover-
nor-General], the exact and detailed topographical boundaries of each of
these districts”, as well as “within the cercles, [to] fix . . . the number and
extent of the territorial subdivisions . . . and the location of their centre”
by means of local decisions.

31. Benin submits that, in the light of these texts, the rules applicable
to the creation of colonies and their subdivisions should be distinguished
from those relating to the establishment of territorial boundaries. At the
hearings, Benin nevertheless acknowledged that the principle whereby
authorities empowered to create colonies or administrative districts were

also competent to define or modify the boundaries thereof was certainly
applicable to colonies. However, Benin contended that such competence
was not exclusive and that in all likelihood the said principle did not
apply in respect of the internal boundaries within colonies. In any event,
the local authorities, headed by the Lieutenant-Governors, had author-

ity, by virtue of the rules governing the fixing of territorial boundaries, to
clarify central authorities’ decisions.
Niger, on the other hand, contends that the power to create colonies,
as conferred by the above-mentioned texts, entailed the implicit power to
establish their overall extent, from which boundaries of varying precision

could be determined on a case-by-case basis. According to Niger, it fol-
lowed from this that the rules concerning the creation and organization
of colonial administrative districts gave implicit prerogatives to the French
metropolitan authorities for the determination of inter-territorial bounda-
ries, and to the authorities of the AOF for the delimitation of adminis-
trative districts and their subdivisions. The Lieutenant-Governors’ com-

petence in this matter was confined to certain specific circumstances,
according to a procedure and formalities laid down by the above-
mentioned texts.

**

32. For a better understanding of the historical context in which the
Parties’ claims stand in relation to the determination of the frontier and

25 FRONTIER DISPUTE (JUDGMENT ) 112

to the question of to whom the islands in the River Niger belong, the
evolution of the legal status of the territories concerned during the colo-

nial period should be briefly recapitulated.
33. In the second half of the nineteenth century, France initially estab-
lished settlements along the coast of Dahomey, at Cotonou and Porto
Novo. Following an armed conflict with the local chieftain in the 1880s
and 1890s, it consolidated its presence in the region first by placing

Dahomey under protectorate (1892), and then by creating the “colony of
Dahomey and dependencies” (decree of 22 June 1894). France subse-
quently launched expeditions northwards from its possessions in Daho-
mey, as well as southwards and eastwards from Sudan, which enabled it,
in the autumn of 1897, to occupy the valley of the River Niger (in par-

ticular the sector between Say and Boussa).
The French occupation was expressly formalized, as regards the region
of north-western Dahomey, by a convention concluded with Germany on
23 July 1897, and as regards north-eastern Dahomey, by a convention
concluded with Great Britain on 14 June 1898. By means of a convention
of 8 April 1904, certain adjustments were made to the line established in

1898 in order to separate the French and British areas of influence. The
parties to that convention fixed the boundaries of their respective posses-
sions in accordance with those adjustments by means of a convention of
29 May 1906 in respect of the region to the east of the River Niger, and
by means of an agreement of 19 October 1906 in respect of the territories

between the Gulf of Guinea and that river; demarcation operations,
documented in an official record dated 19 February 1910, were subse-
quently carried out by the Anglo-French Commission for the delimita-
tion of the territories situated between the Niger and Lake Chad.
34. At the end of the nineteenth century, when the colony of Dahomey

was incorporated into the AOF by decree of 17 October 1899, it encom-
passed, in the region concerned by the present dispute, territories situated
on both banks of the River Niger. By virtue of the same decree, which
had provided for the dissolution of French Sudan and the apportionment
of the territories it had comprised among different colonies and two spe-

cially created military territories, the territory of Say was also attributed
to Dahomey. This territorial incorporation was put into effect by an
arrêté of the Governor of Dahomey dated 20 March 1901.
By arrêté of 23 July 1900, the Governor-General of the AOF decided
to establish a third military territory encompassing the regions on the left
bank of the River Niger from Say to Lake Chad. That 1900 arrêté was

followed by a decree of the President of the French Republic dated
20 December 1900 with the same object. The boundary between the
Third Military Territory and the First Military Territory created in 1899
was subsequently determined by an arrêté of the Governor-General of
the AOF, dated 20 March 1902.

By a decree of 18 October 1904 on the reorganization of the General
Government of the AOF, the President of the French Republic inter alia
established the colony of Haut-Sénégal et Niger comprising “the former

26 FRONTIER DISPUTE JUDGMENT ) 113

territories of Haut-Sénégal and Moyen-Niger and those which form[ed]
the Third Military Territory”. The newly created colony was composed

of “cercles under civil administration” as well as the “Military Territory
of Niger”, constituted by the former First and Third Military Territories.

By decree of 2 March 1907, the cercles of Fada-N’Gourma and Say
were detached from Dahomey and incorporated into the colony of Haut-

Sénégal et Niger. The intercolonial boundary fixed by that decree was
revised on two occasions in its western part, first by a decree of 12 August
1909, and subsequently by a decree of 23 April 1913.
35. On 7 September 1911, a further decree separated the Military Ter-
ritory of Niger from the colony of Haut-Sénégal et Niger (the cercle of

Say remaining as a district of that colony), in order to make it an admin-
istrative subdivision under the direct control of the office of the Govern-
ment-General of the AOF. On 1 January 1921, that military territory
became the Civil Territory of Niger, and was then made an autonomous
colony by decree of 13 October 1922.
In the meantime, the decree of 1 March 1919 had provided for the

establishment of the colony of Haute-Volta, to which were attributed,
inter alia, the cercles of Say and Fada-N’Gourma, which had hitherto
formed part of Haut-Sénégal et Niger.
By decree of 28 December 1926, certain cantons in the cercle of Dori
and the cercle of Say (with the exception of the canton of Gourmanché-

de-Botou) were detached from Haute-Volta and incorporated into Niger.
An arrêté général of 31 August 1927 and the erratum thereto of 5 Octo-
ber of the same year determined the boundary between the colonies of
Haute-Volta and Niger.
The colony of Haute-Volta was abolished by decree of 5 September

1932, then reconstituted with the same territorial basis by Law No. 47-
1707 of 4 September 1947; in the intervening period, the cercles of Fada
and Dori (excluding the canton of Aribinda) were incorporated into
Niger.
36. During the colonial period, the administrative organization of

Dahomey and Niger was the subject of several successive enactments.
Following its establishment in 1894, the colony of Dahomey and
dependencies was organized by arrêté of the Governor ad interim, dated
11 August 1898; that arrêté established four cercles in the colony, includ-
ing that of Moyen-Niger, which comprised inter alia “the territories of
Zaberma or Dendi situated on either side of the Niger and their depen-

dencies” and that of Gourma, which comprised “the provinces of Fada
N’Gourma, Pama, Matiacouali, Kodjar, Botou and their dependencies”.
The territorial divisions of the colony were reorganized by arrêtés of the
Governor-General of the AOF, dated 8 December 1934 and 27 October
1938; those two arrêtés inter alia defined the boundaries of the cercles of

Kandi and of Natitingou, adjoining the colony of Niger.
The internal reorganization of Niger was the subject of successive
arrêtés of the Governor-General of the AOF, dated 26 December 1904,

27 FRONTIER DISPUTE (JUDGMENT ) 114

31 December 1907, 14 December 1908, 22 June 1910, 23 November 1912
and 22 January 1927. On the eve of independence, as a result of an arrêté

général of 30 March 1956 adding seven new cercles to the colony, Niger
comprised 16 cercles.

**

37. The Chamber will now describe the main documents relevant to
the settlement of the frontier dispute. In this connection, a distinction
should be made between those documents that concern the determination

of the course of the boundary in the River Niger sector and the question
of to whom the islands in that river belong and those documents that
relate to the delimitation in the River Mekrou sector.
38. As regards the sector of the River Niger and the islands therein,
the essential documents, in chronological order, are as follows:

— the arrêté général of 23 July 1900 creating a Third Military Territory,
the administrative centre of which was established at Zinder. Article 1

of this arrêté stated that this territory “encompass[ed] the areas on
the left bank of the Niger between Say and Lake Chad that [had
been] placed within the French sphere of influence by the Convention
of 14 June 1898”;
— the decree of 20 December 1900 creating a Third Military Territory

between the Niger and Lake Chad;
— letter No. 163 from the Minister for the Colonies, dated 7 September
1901, addressed to the Governor-General of the AOF. In this letter,
the Minister referred to a previous communication, by which the
Governor-General had transmitted two reports to him from the Gov-

ernor of Dahomey “regarding the question of the delimitation between
Dahomey and the Third Military Territory, and indicating the course
of the Niger as the best demarcation line, both from a geographical
and political perspective”. In response to the Governor-General’s
view that this proposal seemed “highly acceptable”, the Minister indi-

cated in his letter that “on this point, he share[d] [the] view” of the
Governor-General;
— letter No. 54 of 3 July 1914, under cover of which administrateur
adjoint Sadoux, commandant of the secteur of Gaya (Niger), sent to
the commandant of the cercle of Moyen-Niger (Dahomey) “a table of
the islands in the River Niger indicating the major branch of the river

and the colony to which the islands therefore belong[ed]”, which he
had prepared “for the sole purpose of clearly determining when graz-
ing permits [should] be issued to the Peuhls from both banks and
delimiting the territorial jurisdiction of the indigenous tribunals in the
two colonies”. In his letter, the administrateur adjoint indicated that

he “believe[d] . . . that it [was] the main channel that [should] serve as
delimitation” between the territories concerned, “the commandant of
the secteur of Guéné having cited to [him the previous year] a text on

28 FRONTIER DISPUTE (JUDGMENT ) 115

this subject, which [was] in Kandi, but [which he] [did] not have in
Gaya”;

— arrêté général No. 2812/AP of 8 December 1934 and arrêté général
No. 3578/AP of 27 October 1938, both reorganizing the territorial
divisions of the colony of Dahomey. The latter, whose text is virtually
identical to that of 1934 in the part relevant to the present case, indi-
cated in Article 1 that the cercle of Kandi was bounded

“[in] the east, by the frontier of Nigeria [the 1934 arrêté referred to
‘the frontier of Niger’] as far as the Niger;
[i]n the north-east, by the course of the Niger to its confluence with

the Mekrou . . .”.
Article 2 stated that the boundaries of the cercles were those drawn
on a 1:500,000 map of Dahomey appended to the arrêté (Article 2 of

the 1934 arrêté being identical in content). However, neither of the
Parties has been able, for the purposes of the present case, to locate
the maps on which those boundaries had been drawn;
— letter No. 3722/APA of 27 August 1954, by which Secretary-General
Raynier, Governor ad interim of Niger, informed the chef of the sub-

division of Gaya (Niger), through the commandant of the cercle of
Dosso (Niger), “that the boundary of the Territory of Niger [was]
constituted by the line of highest water, on the left bank of the river,
from the village of Bandofay to the frontier of Nigeria” and that
“[c]onsequently, all the islands situated in this part of the river
[formed] part of the Territory of Dahomey”. The Parties have drawn

the attention of the Chamber to other letters relating to the inter-
colonial boundary exchanged between the authorities of Niger,
between the authorities of Dahomey and between the two colonies
during 1954, as well as in subsequent years (in 1956 for example),
which would allegedly make it possible to assess the legal value and

the significance of the aforementioned letter.
39. With respect to the River Mekrou sector, the essential documents

from the colonial period are, in chronological order, as follows:
— a decree of 2 March 1907, incorporating the cercles of Fada
N’Gourma and Say into the colony of Haut-Sénégal et Niger.

Article 1 of this decree provided as follows:
“[t]he boundary between the colony of Haut-Sénégal et Niger and
the colony of Dahomey is formed, from the boundary of Togo, by

the present boundary of the cercle of Gourma until it reaches the
Atakora mountain range, whose summit it follows until it meets
the Paris meridian, from which point it runs in a straight line in a
north-easterly direction, terminating at the confluence of the River
Mekrou with the Niger”;

— a decree of 12 August 1909, Article 1 of which provided that “[t]he
boundary between the cercle of Gourma (Haut-Sénégal et Niger) and

29 FRONTIER DISPUTE (JUDGMENT ) 116

the cercle of Djougou (Dahomey)” was formed, inter alia,by

“[t]he Altacora mountain range, whose summit it follows, or, more
precisely, a line parallel to the Konkobiri-Tandangou-Sangou trail
running along the foot of the mountain, at a distance of 8 km from

the trail”;
— a decree of 23 April 1913, Article 1 of which provided that “[t]he

boundary between the cercles of Fada-N’Gourma (Haut-Sénégal et
Niger) and Atacora (Dahomey)” was determined, inter alia,by

“a line parallel, in the east, to the Compongou-Konkobiri-Batch-
ango trail running along the foot of the Atacora mountain range at
a distance of 8 km from the trail and continuing until it meets the
upper course of the River Pendjari”;

— a decree of 1 March 1919 dividing the colony of Haut-Sénégal et
Niger and creating the colony of Haute-Volta;
—an arrêté général of 16 April 1926 laying down certain conditions for
the implementation of the decree of 10 March 1925 regulating hunt-

ing and creating game parks in the AOF;
—an arrêté général adopted by the Governor-General ad interim of the
AOF on 31 August 1927, fixing the boundaries of the colonies of
Haute-Volta and Niger. Although, as stated by its text, this arrêté
related to the frontier between Haute-Volta and Niger, it provided, in

Article 1, paragraph 2, that the boundaries between the cercle of Say
and Haute-Volta were formed

“[i]n the South-West, [by] a line starting approximately from the
[River] Sirba at the level of the Say parallel and running as far as
the Mekrou;
[i]n the South-East, by the Mekrou from that point as far as its
confluence with the Niger”.

This arrêté général was amended, on this point among others, by an
erratum of 5 October 1927, published in the Journal officiel of the

AOF of 15 October 1927, in which the final subparagraph of Article 1
provided simply that the boundary of the colonies of Niger and
Haute-Volta “follows . . . the course of the Tapoa upstream until it
meets the former boundary of the cercles of Fada and Say, which it
follows as far as its intersection with the course of the Mekrou”;
— the aforementioned arrêtés généraux of 8 December 1934 and

27 October 1938, which indicated, inter alia, that the north-western
boundary of the cercle of Kandi was formed by “the boundary
between Dahomey and the colony of Niger, from the River Niger to
the confluence of the Pendjari with the Kompongou southern
‘marigot’ ”;

— local arrêté No. 1464 APA of the Governor ad interim of Dahomey,
dated 30 September 1937, laying down certain conditions for the
implementation of the decree of 13 October 1936 regulating hunting

30 FRONTIER DISPUTE (JUDGMENT ) 117

in the principal African territories under the jurisdiction of the
Ministry of the Colonies;

— local arrêté No. 1302/AE/SZ of the Governor of Niger, dated
13 November 1937, providing that part of the territory of the cercles
of Niamey and Fada N’Gourma would be set aside for the “Niger W
National Park”;
— arrêté général No. 7640 SE/F of 3 December 1952, designating part

of the cercle of Kandi (Dahomey) as the “Niger W Total Reserve”,
the boundaries of which it fixed;
— arrêté général No. 4676 SE/F of 25 June 1953, creating the “Niger W
Total Game Reserve” in an area situated in the cercle of Niamey
(Niger), the boundaries of which it fixed.

The Parties also discussed, in connection with the frontier in the River
Mekrou sector, the significance of certain documents that are posterior to

the dates of independence, in particular:
— Note Verbale No. 03498, addressed on 29 August 1973 to the Minis-
try of Foreign Affairs of Dahomey by the Ministry of Foreign Affairs

of Niger, concerning the meeting of a joint committee regarding a
joint dam project on the River Mekrou;
— the minutes of a meeting of experts of the Governments of Niger and
Dahomey, held on 8 February 1974, “concerning the Mekrou and the
dam project on that river”;

— the Agreement of 14 January 1999 between Niger and Benin, relating
to the development of a hydroelectric facility at Dyodyonga on the
River Mekrou.

*

40. The Parties also produced a large quantity of cartographic and
photographic material in support of their respective arguments, varying
in date, origin, technical quality and level of accuracy.

41. With regard to the identification of the main channel of the River
Niger and the attribution of the islands in that river between the Parties,
Niger has relied in particular on the following, among many other maps
and sketch-maps: maps of the course of the Niger prepared in 1896 fol-
lowing a mission led by Lieutenant Commander Hourst to study the
régime of the river and its navigability; the general 1:10,000 plan from

the study on the navigability of the stretch of the Niger between Niamey
and Gaya carried out by the mission led by A. Beneyton in 1929-1930;
the map annexed to the report on the survey of the river between Niamey
and Malanville carried out in 1949 on the instructions of the chef des
services of the Benin-Niger region; sheet No. 4 of the study on the navi-

gability of the river (1:10,000 survey of the shoals) prepared in 1965 by
the topographic service and land registry of the Republic of Niger; maps
Nos. 32 to 37 on a scale of 1:50,000 from the study on the navigability of

31 FRONTIER DISPUTE (JUDGMENT ) 118

the River Niger between Tossaye and Yelwa conducted from 1967
onwards by NEDECO, a Dutch firm, at the request of four riparian

States (Dahomey, Mali, Niger and Nigeria), the work on the ground
being carried out in 1968-1969 and the final report produced in Septem-
ber 1970; and sheets Nos. 1 to 4 on a scale of 1:50,000 from the study of
the River Niger in 1979 by the French Institut géographique national
(IGN) on the basis of a photographic mission in April 1975. Niger also

pointed out that the 1:200,000 maps of West Africa published by the
AOF cartographic service in Dakar in 1955 and 1960 situated the inter-
colonial boundary in the course of the river.

For its part, Benin has referred to cartographic material dating from

the colonial period, produced by one or other of the Parties, to demon-
strate that the cartographers never took it for granted that the boundary
between the colonies of Dahomey and Niger followed the navigable
channel of the River Niger. Moreover, according to Benin, the above-
mentioned sketch-maps or studies, relied on by Niger in support of its
argument, cannot be used to define the navigable channel at the dates of

independence or to determine to which of the Parties the islands in the
river belong. Finally, Benin relies on a study carried out for the purposes
of the present case by IGN-France international in December 2003,
which compared the maps of the region published by IGN in 1960 with
SPOT images on the same scale recorded in 2002, in order to show the

changes in the configuration of the widest channel and islands of the
River Niger over the last 50 years.
42. With regard to the River Mekrou sector, each Party has relied on
several maps dating from the colonial period to support its position.

According to Benin, these maps (in particular those prepared after
1919, with the exception of a map dated 1922 and republished in 1928
cited by Niger) confirm that the Mekrou was the intercolonial boundary.
Benin refers, inter alia, to the following cartographic documentation: the
“Kandi” and “Niamey” sheets of the map (1:500,000) prepared and pub-

lished in October 1926 by the AOF Geographical Service (known as the
“Blondel la Rougery map”); the map entitled “New Boundary of Haute-
Volta and Niger (according to the erratum of 5 October 1927 to the
arrêté of 31 August 1927)” (1:1,000,000); an undated map entitled
“Sketch-map of the Colony of Niger prepared by Colonel Abadie of
the Colonial Infantry” (1:4,500,000); a Dahomey-Togo road map

(1:1,000,000) prepared by the AOF Geographical Service in 1938; and a
road sketch-map entitled “Dahomey and Togo” prepared by the same
service in 1948.
Niger has relied on a large amount of cartographic material to show
that the colonial authorities had only a vague knowledge of the River

Mekrou region and of the exact course of that river, and that the bound-
ary established by the decree of 2 March 1907 had never been challenged;
in this connection, it drew the attention of the Chamber to a combined

32 FRONTIER DISPUTE (JUDGMENT ) 119

political and administrative map of the AOF published in 1928 (the
updated version of a similar map prepared in 1922) on which the dates of

2 March 1907 and 6 September 1909 are placed along the line marking
the boundary in the Mekrou sector.
43. Finally, the Parties refer to certain maps in order to determine the
indicative co-ordinates of precise points on their common frontier.
Thus Benin measures the co-ordinates of the tripoints with Burkina

Faso and Nigeria on the basis of the relevant sheets of what it regards as
the most reliable map published on the eve of the independence of the
two States, namely a 1:200,000 map of the AOF produced by the IGN in
1955.
Niger has noted that the co-ordinates of the Benin/Niger bipoint and

of the tripoint with Burkina Faso that it claims in the River Mekrou sec-
tor were plotted on 1:200,000 IGN maps (the Kandi sheet of a map of
West Africa published by the IGN which is annexed to its Memorial).

44. The Chamber would recall here the terms in which the probative
value of maps was described in the Judgment rendered in the case con-

cerning the Frontier Dispute (Burkina Faso/Republic of Mali ):

“maps merely constitute information which varies in accuracy from
case to case; of themselves, and by virtue solely of their existence,
they cannot constitute a territorial title, that is, a document endowed
by international law with intrinsic legal force for the purpose of
establishing territorial rights. Of course, in some cases maps may

acquire such legal force, but where this is so the legal force does not
arise solely from their intrinsic merits: it is because such maps fall
into the category of physical expressions of the will of the State or
States concerned. This is the case, for example, when maps are
annexed to an official text of which they form an integral part.

Except in this clearly defined case, maps are only extrinsic evidence
of varying reliability or unreliability which may be used, along with
other evidence of a circumstantial kind, to establish or reconstitute
the real facts.” (I.C.J. Reports 1986, p. 582, para. 54.)

In other words,
“except when the maps are in the category of a physical expression

of the will of the State, they cannot in themselves alone be treated as
evidence of a frontier, since in that event they would form an irre-
buttable presumption, tantamount in fact to legal title. The only
value they possess is as evidence of an auxiliary or confirmatory
kind, and this also means that they cannot be given the character of

a rebuttable or juris tantum presumption such as to effect a reversal
of the onus of proof.” (Ibid., p. 583, para. 56.)

33 FRONTIER DISPUTE (JUDGMENT ) 120

This principle will also guide the Chamber in its assessment of the
maps relied on by the Parties in the present case.

* * *

45. The Chamber is firstly asked, in accordance with Article 2, para-
graphs (a) and (b), of the Special Agreement, to determine the course of

the boundary in the sector of the River Niger and then to specify to
which Party each of the islands in the river belongs.
As the Chamber has recalled (see paragraph 23 above), the Parties
have expressly asked it to carry out its task on the basis of, in particular,
the principle of the succession of States to the frontiers inherited from

colonialism, namely the principle of the intangibility of such frontiers,
also known as the principle of uti possidetis juris.
46. In the present case these territorial boundaries were no more than
delimitations between different administrative divisions or colonies sub-
ject to the same colonial authority. Only at the moment of independence,
also called the “critical date”, did these boundaries become international

frontiers. Until that time the matter of delimitation was governed by
French colonial law, known as “droit d’outre-mer”. As noted above (see
paragraph 28), in the application of the principle of uti possidetis juris,
French law does not play a role in itself but only as one factual element
among others, or as evidence indicative of what has been called the

“colonial heritage” at the critical date.

Since the Parties achieved independence virtually simultaneously (see
paragraph 20 above), the period between 1 and 3 August 1960 can be
considered as the critical date.

47. In accordance with the approach of the Chamber in the Frontier
Dispute (Burkina Faso/Republic of Mali) case, the Chamber will first
consider the various regulative or administrative acts invoked by the
Parties; thus, pre-eminence is to be accorded to legal title over effective
possession as a basis of sovereignty (I.C.J. Reports 1986, pp. 586-587,

para. 63).
In this respect, it is relevant to recall that the Parties agree that, during
the period under consideration, the power to create colonies or territories
was vested in the President of the French Republic until 1946 and
thereafter in the French Parliament, while colonial subdivisions could
be created by the Governor-General of the AOF under the terms of

the decree of 18 October 1904. In his circular No. 114c of 3 November
1912, the Governor-General of the AOF determined that the main
subdivisions (“cercles”) would be established by the Governor-General,
but that the Lieutenant-Governors would be entitled to create further
territorial subdivisions within the “cercles” (see paragraph 30 above).

It appears that it is not disputed between the Parties that the compe-
tence to create or establish territorial entities included the power to deter-

34 FRONTIER DISPUTE JUDGMENT ) 121

mine their extent and to delimit them, although during the colonial
period this was never made explicit in any regulative or administrative

act.

**

48. As the Chamber has set out above (see paragraphs 32 to 36), the
colony of Dahomey was created by decree of 22 June 1894 and incorpo-
rated into the AOF by decree of 17 October 1899. It is not contested that,

during this period, the colony of Dahomey comprised territories situated
on both banks of the River Niger.
49. By arrêté of 23 July 1900 the Governor-General of the AOF estab-
lished a Third Military Territory, which “will encompass the areas on the
left bank of the Niger between Say and Lake Chad that were placed

within the French sphere of influence by the [Anglo-French] Convention
of 14 June 1898”.
50. On 20 December 1900 a decree of the President of the French
Republic was issued which established a Third Military Territory
“between the Niger and Lake Chad”. The decree, which was superior to
an arrêté in the hierarchy of legal acts, made no reference to the arrêté of

23 July 1900. In the Chamber’s view, the decree must nevertheless be seen
as a confirmation of the arrêté of the Governor-General; it covers, albeit
in less precise terms, the same area between (the River) Niger and (Lake)
Chad.

*

51. Benin contends that the arrêté of 23 July 1900 established the
boundary between the Third Military Territory and the colony of Daho-
mey at the left bank of the River Niger. According to Benin, by detach-
ing the areas beyond the left bank from Dahomey, the river itself and the
islands located therein remained part of that colony. Benin further con-

tends that the boundary thus established was confirmed in 1954 by
Mr. Raynier, Secretary-General and Governor ad interim of Niger, in his
letter of 27 August (see paragraph 38 above).
52. Niger, for its part, denies that the arrêté of 23 July 1900 estab-
lished a boundary; in its view the relevant wording was merely intended
to indicate the territorial extent of the newly created Territory. It further

observes that an understanding soon developed that the boundary was
constituted by “the course of the river” and that this could only mean
that the boundary was situated within the watercourse of the river. As
evidence of this understanding, Niger refers to a letter of the French Min-
ister for the Colonies dated 7 September 1901 (see paragraph 38 above).

It further contends that this understanding was formally confirmed in
two arrêtés of the Governor-General of the AOF of 8 December 1934
and 27 October 1938.

35 FRONTIER DISPUTE (JUDGMENT ) 122

Sketch-map No. 3, on page 123 below, shows the claims of the Parties
in respect of the boundary in the sector of the River Niger.

*

53. The Chamber is of the view that the arrêté of 23 July 1900 in con-
junction with the decree of 20 December 1900, which created the Third

Military Territory, cannot be read as determining the boundaries thereof.
The geographical references used can only be seen as indicating in general
terms the extent of the newly created territory; the words “the areas on
the left bank of the Niger” in the arrêté and “the Niger” in the decree
make it clear that these areas are detached from the colony of Dahomey

to which they previously belonged.

54. The conclusion that the legal instruments of 23 July and 20 Decem-
ber 1900 did not determine any boundary, and were not considered at the
time as doing so, is confirmed by the letter of 7 September 1901 of the
French Minister for the Colonies addressed to the Governor-General of

the AOF. In this letter reference is made to two political reports in which
the Governor of Dahomey indicated with regard to the delimitation
between Dahomey and the Third Military Territory that “the course of
the Niger” would constitute the best demarcation line, both from a geo-
graphical and a political point of view. The Governor-General appar-

ently supported this suggestion and in his reply the Minister wrote that
he “share[d] [the] view [of the Governor-General] on this point”.
55. Although this letter did not determine the boundary, the Chamber
considers that it provides sufficient evidence that a delimitation had not
taken place the year before. Nor has the Chamber found any document

which shows that a delimitation was carried out in subsequent years. The
Chamber notes in this respect that a preparatory draft of the arrêté
général of 23 November 1912 on the internal administrative reorganiza-
tion of the Military Territory of Niger contained a suggestion to locate
the boundary at the right bank of the River Niger, thus allocating all

islands in the river to this Territory, but that this proposal was not fol-
lowed in the arrêté itself which did not contain any delimitation clause.
56. The Chamber therefore concludes that Benin’s argument that the
arrêté of 23 July 1900 located the boundary at the left bank of the River
Niger, and that this delimitation remained in force until the date of
independence, cannot be upheld.

**

57. As noted above (see paragraph 51), Benin contends that the bound-
ary as established in the arrêté of 23 July 1900, was confirmed in a letter

of Mr. Raynier, Governor ad interim of Niger, of 27 August 1954. In this
letter, Mr. Raynier informed the chef of the subdivision of Gaya (Niger)
that “the boundary of the territory of Niger [was] constituted by the

36FRONTIER DISPUTE (JUDGMENT ) 123 FRONTIER DISPUTE (JUDGMENT ) 124

line of highest water, on the left bank of the river, from the village of
Bandofay to the frontier of Nigeria”, and that “[c]onsequently, all the

islands situated in this part of the river [formed] part of the territory of
Dahomey”.
58. According to Benin, this letter both corroborates the existence of
the boundary at the left bank and adds the further precision that it is
constituted by “the line of highest water”. Benin argues that this was not

beyond the competence of a Lieutenant-Governor; the letter must be
deemed to be declaratory in so far as it confirmed and clarified an already
existing title and constitutive in so far as it contained a specification of
that title.
59. Benin further contends that Niger is bound by the letter since it

subsequently became the subject of intercolonial correspondence and was
relied upon by the authorities of Dahomey. The letter was never with-
drawn by its author nor was it invalidated by a higher authority. In
Benin’s view, “for the purposes of applying the uti possidetis principle,
it is thus indeed the 1954 correspondence which constitutes the ‘colonial
heritage’, that is to say, the ‘photograph’ of the territory at the critical

date”.
60. Niger denies that Mr. Raynier was competent to determine an
intercolonial boundary and consequently considers that the letter lacks
any legal basis. It further contends that the letter only refers to one sec-
tion of the limit (between Bandofay and the border with Nigeria) and

therefore cannot determine the whole boundary. Niger finally asserts that
the letter was of an intra-colonial character and never led to an inter-
colonial understanding to which it could be held in good faith.

**

61. The Chamber will first analyse the context in which the letter of
27 August 1954 was written.
From the case file it is clear that in the first half of 1954 difficulties had
arisen between the local authorities in the two colonies about the legal

status of certain islands in the river.
With regard to one of these islands, (“the island opposite Gaya”), the
commandant of the cercle of Kandi (Dahomey) sent a letter dated 17 June
1954 to the Governor of Dahomey asking to whom that island belonged.
On 23 July of the same year the chef of the subdivision of Gaya (Niger)
addressed a more general request to the Governor of Niger, asking for

“all relevant information regarding the islands in the river belonging to
Niger or to Dahomey”.
62. In his response of 1 July 1954 to the first letter, the Governor of
Dahomey stated that “the arrêtés delimiting the boundary between these
two territories [were] silent” on the question of the attribution of the

islands to each colony. He requested the commandant of the cercle of
Kandi to draw up a list of those islands, the status of which could be the
source of dispute, “in order to enable [him] to settle once and for all with

38 FRONTIER DISPUTE (JUDGMENT ) 125

Niger, [with whom he intended to raise] the question, this problem of the
boundary delimitation”.

63. In his reply, dated 27 August 1954, to the request made by the chef
of the subdivision of Gaya, Mr. Raynier, the Governor ad interim of
Niger (who had arrived in Niamey on 25 August 1954), made the state-
ment referred to above (see paragraph 57). No reasoning was given nor
were any references made to earlier regulative or administrative acts. The

commandant of the cercle of Dosso (to which Gaya belonged) sent a copy
of this letter to the commandant of the cercle of Kandi, who in turn trans-
mitted it to the Governor of Dahomey.

64. On 11 December 1954 the Governor of Dahomey asked his counter-

part in Niger “to kindly provide [him] with particulars of the instru-
ments or agreements determining [the] boundaries” mentioned in the
letter of 27 August. The Governor stated that he sought this clarifi-
cation “in order that this question might be officially resolved” since
“Dahomey’s archives and arrêté général No. 3578/AP of 27 October
1938 provide[d] no specific information on the matter”.

The Governor ad interim of Niger never responded to that request.

*
65. The Chamber has already found that the arrêté of 23 July 1900 did

not establish a boundary; consequently, the letter of 27 August 1954 can-
not be seen as an authoritative confirmation of such a boundary.

The Chamber further notes that, under French colonial law, the
Lieutenant-Governor of a colony had no competence to unilaterally

delimit the external boundaries of the colony. The letter in itself cannot,
therefore, be relied on by Benin as a legal title placing the boundary on
the left bank of the river.
66. The boundary defined in the letter could have been validated by a
higher authority and it was with that in mind that the Governor of Daho-

mey asked for further information in his letter of 11 December 1954.
However, the letter of 11 December 1954 went unanswered. Moreover,
no further action was taken by either of the two colonies in order to have
the boundary indicated in the letter of 27 August 1954 validated by the
Governor-General of the AOF. The Chamber therefore cannot uphold
Benin’s claim according to which the letter of 27 August 1954 in conjunc-

tion with the arrêté of 23 July 1900 provides it with legal title to a bound-
ary on the left bank.
67. With regard to Benin’s contention that the letter led to some sort
of informal intercolonial understanding which bound Niger at the critical
date in 1960, the Chamber observes that such a legal concept did not

exist in French colonial law or “droit d’outre-mer” thus cannot provide
Benin with title.
The Chamber is, however, aware of the fact that the letter of 27 August

39 FRONTIER DISPUTE (JUDGMENT ) 126

1954 may have led to certain effectivités. Whether or not this is the case
will be considered in due course.

**

68. The Chamber will now turn to the acts invoked by Niger as evi-
dence of its legal title, namely the arrêtés issued by the Governor-General

of the AOF on 8 December 1934 and 27 October 1938 reorganizing the
internal administrative structure of the colony of Dahomey and contain-
ing a description of the boundaries of the various cercles. In both arrêtés
the north-west boundary of the cercle of Kandi is described as “the
course of the Niger as far as its confluence with the Mekrou”.

69. According to Niger these arrêtés are the formal and authoritative
confirmation that the boundary between Dahomey and the neighbouring
colony of Niger was located in the watercourse itself, as had already been
indicated in the letter of the Minister for the Colonies dated 7 September
1901. The arrêtés thus provide sufficient evidence of Niger’s title, even if

the title itself is not explicitly laid down in a prior regulative or adminis-
trative act.
70. Benin contends that these arrêtés were merely of an intra-colonial
character and were not intended to determine the boundary of Dahomey
with another colony. Benin further argues that the wording used is

imprecise and does not exclude a frontier on the left bank of the river.

*

71. The Chamber first notes that both arrêtés were issued by the
Governor-General, who was the authority competent to establish, delimit
and reorganize the cercles of colonies. In so far as they describe the boun-
daries of these cercles with the neighbouring colonies which also came
under his authority, the arrêtés do not have an exclusive internal charac-

ter but may also be relied upon in intercolonial relations. Consequently it
can be concluded on the basis of these arrêtés that the course of the River
Niger constituted the intercolonial boundary.
72. The Chamber is unable, however, to deduce therefrom that that
boundary was situated in the river, whether at the thalweg or the median
line. The Chamber notes in this regard that the terminology used in the

arrêtés is identical to that of the 1901 letter and is just as imprecise. The
notion of the “course of the river” covers a range of possibilities: a
boundary on either river bank or a boundary somewhere within the river.

73. Even if, as Niger contends, a certain practice had evolved on the

basis of a boundary within the river (see paragraph 83 below), that prac-
tice was not endorsed by the arrêtés, although it may be assumed that the
Governor-General would have been aware of the practice, which had

40 FRONTIER DISPUTE JUDGMENT ) 127

already been in existence for a considerable period of time. In the Cham-
ber’s view, it is evident that the term, “the course of the Niger”, was not

intended to indicate the precise location of the boundary but merely to
indicate the separation line between the two colonies.
74. The Chamber thus finds that the 1934 and 1938 arrêtés do not
establish a boundary in the river; it cannot therefore sustain Niger’s
claims as to title.

**

75. In view of the foregoing, the Chamber concludes that neither of
the Parties has succeeded in providing evidence of title on the basis of

regulative or administrative acts during the colonial period.
76. Therefore, the Chamber will now consider whether the evidence
furnished by the Parties with respect to effectivités can provide the basis
for it to determine the course of the frontier in the sector of the River
Niger and to which of the two States each of the islands in the river
belongs, in particular the island of Lété.

77. The Chamber recalls in this regard that the Court has previously
ruled in a number of cases on the legal relationship between effectivités
and title.
The passage most pertinent to the present case can be found in the
Judgment in the Frontier Dispute (Burkina Faso/Republic of Mali) case,

in which the Chamber of the Court, having noted that “a distinction
must be drawn among several eventualities” when evaluating the legal
relationship between effectivités and title, stated, inter alia, that: “[i]n the
event that the effectivité does not co-exist with any legal title, it must
invariably be taken into consideration” (I.C.J. Reports 1986, p. 587,

para. 63; see also Territorial Dispute (Libyan Arab Jamahiriya/Chad),
Judgment, I.C.J. Reports 1994, p. 38, paras. 75-76; Land and Maritime
Boundary between Cameroon and Nigeria (Cameroon v. Nigeria: Equa-
torial Guinea intervening), Judgment, I.C.J. Reports 2002 , p. 353,
para. 68; Sovereignty over Pulau Ligitan and Pulau Sipadan (Indonesia/

Malaysia), Judgment, I.C.J. Reports 2002 , p. 678, para. 126).

*
78. Both Parties claim that, during the colonial period, administrative

acts were carried out by their local colonial authorities on a number of
islands in the river. The Parties mention, in this regard, the provision of
licences for grazing, fishing and tree-felling, as well as the levying of
taxes, periodic sanitary control of livestock, military patrolling and police
activities.

79. With regard to the management of the river, Niger claims that, for
a certain period, it carried out management activities over the whole of
the relevant stretch of the river. Niger further maintains that, when this

41 FRONTIER DISPUTE JUDGMENT ) 128

task was subsequently entrusted to Dahomey, the latter did not manage
the whole of the river and that the colony of Niger continued to perform

certain management activities on the part of the river contiguous to it. In
Niger’s view, its continued activities negate Dahomey’s alleged rights on
the whole of the river.

Benin denies that such river management activities can be relied upon

as effectivités since, during the colonial period, such activities, even if
carried out by the authorities of individual colonies, were performed in
the exercise of a public function on behalf of the AOF as a whole.

80. Aside from documentary evidence, Benin has presented testimony

taken from certain individuals in the form of “sommations interpella-
tives” (replies to official enquiries). According to Niger, such testimony,
taken several decades after the period in question, is unreliable and
untrustworthy.
The Chamber notes that Benin did not invoke this testimony in the
later stages of the proceedings.

81. Finally, both Parties have presented a number of maps in order to
support their claims. Neither of them claims, however, that these maps
have any “intrinsic legal force” in the sense that they represent the
“physical expressions of the will of the State . . . concerned” (see Frontier
Dispute (Burkina Faso/Republic of Mali), I.C.J. Reports 1986 , p. 582,

para. 54; see also paragraph 44 above). The Chamber notes that none of
these maps were annexes to an official text.

*

82. The Chamber will first analyse the various activities prior to 1954,
presented as effectivités by the Parties.
83. On 3 July 1914 the commandant of the secteur of Gaya (Niger),
administrateur adjoint Sadoux, wrote a letter to the commandant of the
cercle of Moyen-Niger (Dahomey), in which he referred to the use of cer-

tain islands by the local inhabitants of both banks of the river. He wrote
this letter “for the sole purpose of clearly determining when grazing per-
mits [should] be issued to the Peuhls from both banks and delimiting the
territorial jurisdiction of the indigenous tribunals in the two colonies”.
Administrateur adjoint Sadoux attached to his letter a list of islands in the
border area, drawn up on the basis of an exploration of the whole stretch

of the river between Koulou and the Nigerian border, with an indication
of the colony to which each island belonged according to its position with
respect to the main navigable channel. Administrateur adjoint Sadoux
defined this channel as “the river’s main channel, not the widest channel,
but the only channel navigable at low water ” (emphasis in the original).

84. In his letter, administrateur adjoint Sadoux invited the comman-
dant of the cercle of Moyen-Niger to come to Gaya for further discus-

42 FRONTIER DISPUTE (JUDGMENT ) 129

sions if the contents of the list were contested. The case file does not
contain a reaction to the letter. However, it appears that such a meeting

did take place and led to an agreement.
Thus, in a report entitled “Monographie de Gaya” dated May 1917,
Mr. Esperet, who was heading ad interim the subdivision of Gaya, stated:

“In July 1914 the commandant of the subdivision of Gaya held
consultations on site with the commandant of the cercle of Kandy,
and they proposed to their respective heads of colony that the per-

manently navigable channel of the Niger solely be taken as the
boundary. Although those proposals were never officially approved,
they have since then always served as the basis for the settlement of
any disputes between different groups of Peuhls.”

He also mentioned that “the village of Lété” was administered by Gaya.

85. Although difficulties arose in 1919 with regard to the administra-
tion of the island of Lété by Gaya, which was contested by Dahomey, the
1914 arrangement, which became known as the 1914 modus vivendi,
seems to have been complied with in subsequent years.
In 1925 a proposal was made by Dahomey to exchange Lété for the

three islands opposite Gaya, which the Sadoux letter had attributed to
Dahomey. Asked for his reaction by the Governor of Niger, the comman-
dant of the cercle of Niamey (Niger) stated that the situation, based on
the modus vivendi, was not wholly satisfactory. He therefore suggested
that

“a clearer boundary be adopted: . . . the boundary between the two

colonies is marked by the right bank of the river at the line of highest
water. That will give all the islands to the colony of Niger without
any possibility of dispute.”

No action was taken upon either the proposal of Dahomey or that of
the commandant of the cercle of Niamey.
86. The case file does not contain other documents from that period
referring to the boundary issue; the 1914 modus vivendi seems to have

functioned satisfactorily until the events of 1954 which led to the corre-
spondence described in paragraphs 61 to 64 above. In a telegram of
10 June 1941 to the commandant of the cercle of Dosso (Niger), the chef
of the subdivision of Gaya referred to the 1914 modus vivendi. He com-
mented that:

“[t]he permanently navigable channel of the Niger was solely adopted

as boundary. Those proposals have never been officially approved
since 1914. A decision on the matter is desirable.” (Emphasis in the
original.)

43 FRONTIER DISPUTE (JUDGMENT ) 130

87. In the years prior to 1954, the island of Lété seems to have been
continuously administered by the subdivision of Gaya. The tax registers

of Gaya, in so far as they have been preserved, contain references to
“Lété” in the years 1925, 1927, 1928, 1930, 1932, 1935 and 1936.
“Lété” was included in a list of villages situated in the subdivision of
Gaya, with an indication of the number of inhabitants, in 1932, 1945,
1946 and 1954. It was also included in census lists in 1944 and 1945.

Finally, the Governor of Niger authorized the felling of palm trees on
the island of Lété in 1946.
88. Benin has not submitted any official document from colonial
authorities regarding an effective exercise of authority, during the period

under consideration, on the island of Lété or on any other island situated
to the left of the main navigable channel.

*
89. The Chamber will now turn to the effectivités in the period from

1954 until the critical date in 1960. It recalls that, on 27 August 1954, the
Governor ad interim of Niger wrote a letter in which he stated that the
boundary was situated “at the line of highest water, on the left bank of
the river, from the village of Bandofay to the frontier of Nigeria” and
that “all the islands situated in this part of the river [formed] part of the

territory of Dahomey”.
90. During this period, the claims of Dahomey to be entitled to admin-
ister the island of Lété became more frequent.
In a letter of 23 May 1955 to the commandant of the cercle of Kandi,
the chef de poste administratif at Malanville (Dahomey) mentioned cer-

tain difficulties which had arisen with respect to the collection of taxes
from inhabitants of Niger who held cattle on Lété. He raised the question
of “whether the tax collector of Dahomey [was] entitled to operate on the
island of Lété”.
In a letter of 20 June 1955 to the commandant of the cercle of Dosso

(Niger), dealing with the same incidents, the chef of the subdivision of
Gaya, “without in any way wishing to raise the question of the bound-
ary” (a clear reference to the letter of 27 August 1954), emphasized that
the island of Lété “[had] consistently been regarded as belonging to
Niger”.
91. In 1956, difficulties arose again, this time with regard to the collec-

tion of taxes on the export of smoked fish from Lété. The commandant of
the cercle of Kandi informed the Governor of Dahomey of these inci-
dents and added that he had “rediscovered” the letter of 27 August 1954
which stated that the river and all the islands belonged to Dahomey.

92. In that same year, the Director of the Geographical Service of the
AOF requested the commandants of the cercles of Dosso and Kandi to
inform him of the nature and date of the official texts that defined the

44 FRONTIER DISPUTE (JUDGMENT ) 131

boundary between Dahomey and Niger. In this regard, the chef of the
subdivision of Gaya informed the commandant of the cercle of Dosso that

he had “rediscovered” the 1914 Sadoux letter, which he called “the only
serious document on the matter”.
The commandant of the cercle of Kandi, by letter of 28 June 1956,
informed the Director of the Geographical Service that “this question of
boundaries [had], to [his] knowledge, never been dealt with in any official

text”. He added that there had been disputes in the past and attached in
this regard the letter of 27 August 1954 of the Governor ad interim of
Niger.
93. In 1955, 1957 and 1958, “Lété” is mentioned in the list of polling
stations in Niger.

94. Serious troubles arose in 1959, the year before independence. In a
letter of 16 June 1959 the chef of the subdivision of Malanville informed
the Prime Minister of Dahomey (which was at the time an autonomous
republic within the Communauté française) about a dispute between
inhabitants of Gouroubéri (Dahomey) and Peuhls from Niger who, in
violation of the property rights of the former, had occupied the island

of Lété. He added that he had had unsuccessful consultations with his
counterpart in Gaya, who seemed to support the Peuhls and “[was] . . .
unaware of the régime governing the islands”. The chef of the subdivision
of Malanville was of the view that the boundary was located on the left
bank of the river and stated that, according to his information, the island

of Lété had always belonged to the inhabitants of Gouroubéri.
95. In December 1959, the commandant of the cercle of Kandi visited
Malanville. The chef of the subdivision of Gaya was invited to meet him
on Lété but that meeting did not take place. Although the commandant
of the cercle of Kandi visited the island, the chef of the subdivision of

Gaya “did not come to the meeting”. It was said later on that he had
been unaware of the visit.
96. Riots broke out on the night of 29 June 1960, during which four
Peuhls from Niger were killed and a number of dwellings were set on fire.
In a letter dated 3 July 1960, the commandant of the cercle of Kandi

informed the Minister for the Interior of Dahomey that order had been
restored and that both Gaya (Niger) and Malanville (Dahomey) had
stationed a small police unit on the island.
97. In a letter dated 13 July 1960 to the Prime Minister of Dahomey,
the President of the Council of Ministers of Niger (which was also at the
time an autonomous republic within the Communauté française) pro-

posed to settle the dispute for once and for all through a formal agree-
ment on the question of the “island of Lété (subdivision of Gaya, Niger)”.

In his response dated 29 July 1960, the Prime Minister of Dahomey
observed that the matter had already been settled by the letter of

27 August 1954 but that he did not object to consultations in order to
reach a formal agreement.
In a letter dated 31 July 1960, the Prime Minister of Niger again

45 FRONTIER DISPUTE (JUDGMENT ) 132

pressed for a formal settlement. He referred, however, not to the 1954
letter but, inter alia, to the 1914 letter and proposed to take as the bound-

ary “the median line of the river’s permanent channel, or of its deepest
channel”.

*

98. On the basis of the evidence before it, the Chamber finds that,
from 1914 to 1954, the terms of the modus vivendi established by the 1914
Sadoux letter were in general respected and that, during this period, the
main navigable channel of the River Niger was considered by both sides
to be the boundary. As a result, administrative authority was exercised

by Niger on the islands to the left and by Dahomey on the islands to the
right of that line. The entitlement of Niger to administer the island of
Lété was sporadically called into question for practical reasons but was
neither legally nor factually contested.

99. With respect to the islands opposite Gaya, the Chamber notes

that, on the basis of the modus vivendi established by the 1914 Sadoux
letter, these islands were considered to fall under the jurisdiction of
Dahomey. It recalls in this regard that in 1925 a proposal was made to
Niger by the authorities of Dahomey for the exchange of the three islands
opposite Gaya for the island of Lété but that no action was taken on this

proposal (see paragraph 85 above). The Chamber has not received any
information to indicate that these islands were administered at that time
from anywhere else other than the cercle of Kandi (Dahomey). The
Chamber therefore concludes that, in this sector of the river, the bound-
ary was regarded as passing to the left of these three islands.

100. The situation is less clear in the period between 1954 and 1960. It
is apparent that both Parties periodically claimed rights over the islands,
in particular Lété, and also occasionally performed administrative acts as
a display of authority. However, on the basis of the evidence before it,
the Chamber cannot conclude that the administration of Lété, which

before 1954 was undoubtedly carried out by Niger, was effectively trans-
ferred to or taken over by Dahomey. In this respect, the Chamber notes
that a report of the gendarmerie of Malanville of 1 July 1960 stated that
Lété was “currently administered by the subdivision of Gaya”.

*

101. Benin contends that, even if the local authorities in Niger did
administer Lété and other islands during the period between 1914 and

1954, they could not have done so in the belief that they were acting “as
of right”.
In Benin’s view, the modus vivendi was merely a temporary and prac-

46 FRONTIER DISPUTE (JUDGMENT ) 133

tical arrangement, pending a definitive settlement of the boundary issue.
By its very nature, it precluded the existence of an intention to act “as of

right” and these administrative acts cannot therefore be relied on as
effectivités.
As regards the period after 1954, Benin contends that Niger had, in the
letter of 27 August 1954, relinquished any intention to act “as of right”.

102. The Chamber observes that the concept of the intention and will
to act as sovereign, as mentioned in the Legal Status of Eastern Green-
land (Denmark v. Norway) case (1933, P.C.I.J., Series A/B, No. 53 ,
pp. 45-46), is a concept of international law and cannot be transplanted
purely and simply to colonial law. The Chamber’s sole task in applying

the principle of uti possidetis juris is to ascertain whether it was the
colony of Dahomey or that of Niger which effectively exercised authority
over the areas which the Parties now claim as sovereign States.

*

103. For all these reasons and in the circumstances of the case, par-
ticularly in light of the evidence furnished by the Parties, the Chamber
concludes that the boundary between Benin and Niger follows the main
navigable channel of the River Niger as it existed at the dates of inde-

pendence, it being understood that, in the vicinity of the three islands
opposite Gaya, the boundary passes to the left of these islands. Conse-
quently, Benin has title to the islands situated between the boundary thus
defined and the right bank of the river and Niger has title to the islands
between that boundary and the left bank of the river.

**

104. The Chamber will now proceed to determine the precise location
of the boundary line in the main navigable channel, namely the line of

deepest soundings, as it existed at the dates of independence; it will then
determine to which of the Parties each of the islands in the river belongs.

105. Benin contends that the navigable channel of the River Niger
is unstable and has changed over the years as the result of the siltation
of the river and the formation of sandbanks of a virtually permanent

character. Benin has highlighted a number of cases in which this pheno-
menon has allegedly resulted in a change in the position of the main
navigable channel around the islands. It referred, in particular, to the
islands of Kotcha Barou, Gagno Goungou and Dolé Barou.
106. Niger does not deny the periodic occurrence of siltation which

may lead to the formation of sandbanks but contends that, under normal
circumstances, these accumulations of sand are washed away during the
high-water season when the speed and pressure of the watermass increase

47 FRONTIER DISPUTE (JUDGMENT ) 134

considerably. Niger admits that, with respect to the island of Dolé Barou,
the main channel has moved to the left side of the island since the acces-

sion of the two States to independence, but submits that this may be due
to works on dykes carried out upstream on the left bank of the river. It
further submits that a number of hydrological surveys, carried out over a
period of more than 60 years, have demonstrated that the riverbed is
remarkably stable and that the main navigable channel has remained

unchanged.

107. The Chamber initially notes that, over the course of time, a
number of hydrographic and topographic surveys have taken place. In
this respect, the following studies are the most pertinent:

1. the maps produced as a result of the mission of Lieutenant Hourst in
1896;
2. the report of the mission carried out by the engineer A. M. J. Beney-
ton between 1926 and 1932 on behalf of the AOF;
3. the final report of a study on the navigability of the Middle Niger,

carried out by the Netherlands Engineering Consultants (NEDECO)
between 1967 and 1970 at the request of the Governments of Daho-
mey, Mali, Niger and the Federation of Nigeria;
4. a series of annotated aerial photographs taken in 1975 and published
in a report of IGN-Paris in 1979.

108. The Chamber observes that the position of the main navigable
channel as determined by each of the missions is very similar. The
Chamber considers that this indicates that the riverbed is relatively
stable and that any siltation which has taken place has rarely led to a

noticeable change in the location of the main navigable channel. This
appears to have been the case in both the colonial and post-independence
period.
109. Given that the Chamber has to determine the course of the
boundary at the time of independence, the NEDECO report of 1970 pro-

vides the most useful information on the situation at the critical date. In
view of the proven stability of the riverbed, it may be assumed that the
situation between 1967 and 1970 was virtually identical with that in 1960.

110. In this respect, the Chamber considers it of great importance that
the 1967-1970 survey was carried out by an independent firm renowned

for its expertise and experience and that the results were contained in a
report presented to the Governments of four riparian States, including
the Parties to the present case. Furthermore, the findings of the NEDECO
study were not contested at the time of their publication and they are
corroborated by both earlier and later studies.

111. The report of the NEDECO study examines the navigability of
the River Niger between Tossaye in Mali and Yelwa in Nigeria. It there-

48 FRONTIER DISPUTE (JUDGMENT ) 135

fore covers the whole stretch of the river between Benin and Niger from
its confluence with the Mekrou to the frontier with Nigeria.

112. The maps annexed to the report are very detailed, each of them
covering a stretch of 25 km and showing the longitudinal profile of the
main navigable channel based on the results of echosounding carried out,
using a boat-mounted echo-sounder, on various occasions during the
high and low water season. In order to check the position of the channel,

cross-sections were made by NEDECO and the deepest point of each sec-
tion was fixed. Subsequently, the distance was measured from this point
to the two banks, or in certain cases to one of them. Finally, these dis-
tances were represented on a topographical map on a scale of 1:50,000.

The Chamber observes that the main navigable channel identified by
the report of the NEDECO study generally coincides with or is very simi-
lar to the one that is represented in the maps and sketch-maps resulting
from the 1896 Hourst mission and the 1926-1932 Beneyton mission.
113. The Chamber further notes that map No. 36 of the NEDECO

report indicates that in the sector opposite the village of Gaya, the river
has two navigable channels. On the basis of the available data, it is not
possible to say which one is consistently deeper. This is however without
consequence in the present case given the conclusions drawn by the
Chamber, in paragraphs 99 and 103 above, from the colonial effectivités

in that sector. The Chamber considers that, in the sector of the three
islands opposite Gaya, the boundary is constituted by the line of deepest
soundings of the left navigable channel. However, in the vicinity of the
last of these islands, Kata Goungou, the boundary deviates from that line
and passes to the left of that island.

114. With the exception indicated in the previous paragraph, the
boundary between the Parties therefore follows the line of deepest sound-
ings of the main navigable channel of the River Niger as it appears in the
1970 NEDECO report, from the intersection of this line with the median

line of the River Mekrou until its intersection with the boundary of the
Parties with Nigeria.
Opposite Gaya, the boundary is constituted by the line of deepest
soundings of the left navigable channel from the point situated at co-
ordinates 11°52′29″ latitude North and 3°25′34″ longitude East until
the point located at co-ordinates 11°51′55″ latitude North and 3°27′41″

longitude East, where the boundary deviates from this channel and passes
to the left of the island of Kata Goungou, subsequently rejoining the
main navigable channel at the point located at co-ordinates 11°51′41″
latitude North and 3°28′53″ longitude East.
115. It follows from the foregoing that the boundary line between

Benin and Niger in the sector of the River Niger, proceeding down-
stream, passes through the points numbered from 1 to 154, the co-ordi-
nates of which are indicated in the table below:

49 FRONTIER DISPUTE (JUDGMENT ) 136

(Clarke 1880 Ellipsoid)

Co-ordinates on the line
Point No. Latitude North Longitude East

001 12°24′31″ 2°49′36″
002 12°24′25″ 2°50′08″
003 12°24′24″ 2°50′20″
004 12°24′06″ 2°50′43″
005 12°23′54″ 2°50′55″

006 12°23′46″ 2°51′05″
007 12°23′34″ 2°51′25″
008 12°23′32″ 2°51′45″
009 12°23′25″ 2°52′07″
010 12°23′16″ 2°52′21″

011 12°22′56″ 2°52′40″
012 12°22′41″ 2°52′52″
013 12°22′38″ 2°53′04″
014 12°22′00″ 2°53′18″
015 12°21′38″ 2°53′33″
016 12°21′11″ 2°54′04″

017 12°21′07″ 2°54′16″
018 12°20′58″ 2°54′25″
019 12°20′36″ 2°54′52″
020 12°20′12″ 2°55′19″
021 12°20′09″ 2°55′25″
022 12°20′06″ 2°55′38″

023 12°19′41″ 2°56′01″
024 12°19′29″ 2°56′08″
025 12°19′06″ 2°56′29″
026 12°19′00″ 2°56′40″
027 12°18′14″ 2°57′11″

028 12°17′55″ 2°57′16″
029 12°17′15″ 2°57′47″
030 12°17′03″ 2°58′10″
031 12°16′52″ 2°58′41″
032 12°16′38″ 2°59′32″
033 12°16′10″ 3°00′35″

034 12°15′59″ 3°00′49″
035 12°15′26″ 3°01′10″
036 12°15′01″ 3°01′18″
037 12°14′27″ 3°01′31″
038 12°14′01″ 3°01′47″

039 12°13′43″ 3°02′04″
040 12°13′41″ 3°02′11″
041 12°13′34″ 3°02′24″
042 12°13′12″ 3°02′45″
043 12°12′31″ 3°03′33″

50 FRONTIER DISPUTE (JUDGMENT ) 137

Co-ordinates on the line

Point No. Latitude North Longitude East

044 12°12′22″ 3°03′36″
045 12°12′06″ 3°03′29″
046 12°11′46″ 3°03′35″
047 12°11′01″ 3°04′19″
048 12°10′36″ 3°04′56″
049 12°10′26″ 3°05′49″

050 12°10′21″ 3°06′03″
051 12°10′05″ 3°06′25″
052 12°09′46″ 3°06′50″
053 12°09′27″ 3°07′30″
054 12°09′16″ 3°07′40″

055 12°08′52″ 3°07′39″
056 12°08′25″ 3°07′38″
057 12°08′10″ 3°07′59″
058 12°07′48″ 3°08′41″
059 12°07′21″ 3°09′15″
060 12°06′49″ 3°10′07″

061 12°06′21″ 3°10′35″
062 12°05′43″ 3°10′58″
063 12°05′24″ 3°11′07″
064 12°05′01″ 3°11′20″
065 12°04′44″ 3°11′39″
066 12°04′33″ 3°11′54″

067 12°04′24″ 3°12′04″
068 12°04′09″ 3°12′22″
069 12°03′58″ 3°12′43″
070 12°03′39″ 3°13′13″
071 12°03′20″ 3°13′29″

072 12°03′01″ 3°13′49″
073 12°02′51″ 3°13′57″
074 12°02′18″ 3°14′05″
075 12°01′57″ 3°14′22″
076 12°01′53″ 3°14′36″
077 12°01′54″ 3°15′06″

078 12°01′30″ 3°15′33″
079 12°01′10″ 3°15′39″
080 12°00′53″ 3°16′13″
081 12°00′42″ 3°16′13″
082 12°00′21″ 3°15′54″

083 12°00′09″ 3°15′38″
084 11°59′52″ 3°15′25″
085 11°59′24″ 3°15′34″
086 11°58′54″ 3°16′08″
087 11°58′33″ 3°16′21″

51 FRONTIER DISPUTE (JUDGMENT ) 138

Co-ordinates on the line

Point No. Latitude North Longitude East

088 11°58′14″ 3°16′30″
089 11°57′56″ 3°16′42″
090 11°57′19″ 3°16′51″
091 11°56′40″ 3°16′45″
092 11°56′07″ 3°17′00″
093 11°56′01″ 3°17′47″

094 11°55′55″ 3°17′56″
095 11°55′48″ 3°18′00″
096 11°55′01″ 3°18′13″
097 11°54′51″ 3°18′13″
098 11°54′42″ 3°18′12″

099 11°54′12″ 3°18′15″
100 11°53′20″ 3°18′50″
101 11°53′08″ 3°19′06″
102 11°52′54″ 3°19′17″
103 11°52′53″ 3°19′43″
104 11°53′11″ 3°20′15″

105 11°53′09″ 3°20′23″
106 11°52′57″ 3°20′43″
107 11°53′08″ 3°21′38″
108 11°53′13″ 3°22′13″
109 11°53′13″ 3°22′37″
110 11°53′11″ 3°23′01″

111 11°52′59″ 3°23′37″
112 11°52′39″ 3°24′11″
113 11°52′37″ 3°24′44″
114 11°52′43″ 3°25′06″
115 11°52′29″ 3°25′34″

116 11°52′30″ 3°25′55″
117 11°52′37″ 3°26′28″
118 11°52′30″ 3°26′50″
119 11°51′55″ 3°27′41″
120 11°51′53″ 3°28′20″
121 11°51′41″ 3°28′53″

122 11°51′25″ 3°29′12″
123 11°51′03″ 3°29′22″
124 11°50′36″ 3°29′38″
125 11°50′03″ 3°30′11″
126 11°49′39″ 3°30′34″

127 11°49′22″ 3°30′53″
128 11°48′53″ 3°31′16″
129 11°48′29″ 3°31′15″
130 11°48′01″ 3°31′10″
131 11°47′34″ 3°31′13″

52 FRONTIER DISPUTE JUDGMENT ) 139

Co-ordinates on the line

Point No. Latitude North Longitude East
132 11°47′16″ 3°31′22″

133 11°47′06″ 3°31′35″
134 11°46′56″ 3°31′51″
135 11°46′46″ 3°32′06″
136 11°46′41″ 3°32′31″
137 11°46′42″ 3°32′51″

138 11°46′46″ 3°33′13″
139 11°46′45″ 3°33′31″
140 11°46′33″ 3°33′46″
141 11°46′21″ 3°33′53″
142 11°46′09″ 3°33′56″

143 11°45′53″ 3°33′55″
144 11°45′35″ 3°33′45″
145 11°45′06″ 3°33′15″
146 11°44′32″ 3°33′02″
147 11°44′05″ 3°32′59″

148 11°43′27″ 3°33′23″
149 11°43′16″ 3°33′42″
150 11°43′08″ 3°34′07″
151 11°43′11″ 3°34′16″
152 11°42′58″ 3°34′38″

153 11°42′52″ 3°34′58″
154 11°42′39″ 3°35′18″

The points that constitute the boundary line are further represented,
purely for illustrative purposes, on sketch-map No. 4 (in six sheets)
attached to the present Judgment .

*
116. The Chamber will now determine to which of the Parties each of

the islands in the River Niger belongs, following the course of the river
downstream from its confluence with the Mekrou to the frontier with
Nigeria.
The Chamber has not received reliable information that new islands
formed nor that islands disappeared between 1960 and 1967-1970. As

regards subsequent years, it observes that one of the islands identified by
Niger, namely Sandi Tounga Barou, which is not represented on any
map prepared before 1973, does appear on various aerial photographs
and SPOT images taken from 1973 onwards. The Chamber must conse-
quently determine to which of the Parties this island belongs. With

1A copy of this map will be found in a pocket at the end of this fascicle or inside the
back cover of the volume of I.C.J. Reports 2005. [Note by the Registry.]

53 FRONTIER DISPUTE (JUDGMENT ) 140

respect to the “island” of Pekinga, which Niger in its final submissions
attributed to Benin, the Chamber notes that it is not identifiable as a

separate island on the maps annexed to the NEDECO report, but instead
appears to be part of the river bank on the Benin side.

117. The Chamber finds, on the basis of paragraphs 103 et seq.,
that

1. Boumba Barou Béri belongs to Niger;
2. Boumba Barou Kaïna belongs to Niger;

3. Kouassi Barou belongs to Niger;
4. Sansan Goungou, also known as Fodofey (or Fandofay) Barou or
Koro Kouara Barou, belongs to Niger;
5. Lété Goungou belongs to Niger;
6. Tondi Kwaria Barou, also known as Faran Tounga Barou, belongs

to Benin;
7. Monboye Tounga belongs to Niger;
8. Sini Goungou, also known as Tondika Goungou, belongs to Niger;

9. Lama Barou belongs to Niger;
10. Kotcha Barou, also known as Bagou Barou, Gouandi Tounga Barou

or Ibrahim Ba Ama Founbou, belongs to Niger;
11. Koki Barou belongs to Benin;
12. Gagno Goungou, also known as Gaya Goungou or Karsani
Goungou, belongs to Benin;
13. Kata Goungou belongs to Benin;

14. Sandi Tounga Barou belongs to Benin;
15. Gandégabi Barou Kaïna belongs to Benin;
16. Gandégabi Barou Béri belongs to Niger;
17. Guirawa Barou, also known as Issa Kaïna, belongs to Niger;

18. Dan Koré Guirawa, also known as Bédari, belongs to Benin;

19. Barou Elhadji Dan Djoda, also known as Sabonbarou or Wéra
Barou, belongs to Benin;
20. Koundou Barou belongs to Benin;

21. Elhadji Chaïbou Barou Béri belongs to Niger;
22. Elhadji Chaïbou Barou Kaïna belongs to Niger;
23. Goussou Barou, also known as Gattawani Béri Barou or Dandani-
koye Barou, belongs to Niger;
24. Beyo Barou, also known as Wéra Kaïna Barou, belongs to Niger;

25. Dolé Barou, also known as Barou Béri or Bani Koubaye, belongs to
Niger.

These various islands are shown on the illustrative sketch-map referred
to in paragraph 115 above.
118. Finally, the Chamber observes that the determination in regard

54 FRONTIER DISPUTE (JUDGMENT ) 141

to the attribution of islands effected above is without prejudice to any
private law rights which may be held in respect of those islands.

**

119. Niger has also asked the Chamber to determine the frontier on
the two bridges between Gaya (Niger) and Malanville (Benin). Benin

contends that this issue is not covered by the dispute submitted to
the Chamber under the terms of the Special Agreement and that the
Chamber therefore has no jurisdiction to comply with Niger’s request.
120. The Chamber notes in this regard that, in the Special Agreement,
“[t]he Court is requested to . . . determine the course of the boundary . . .

in the River Niger sector”. Since the bridges between Gaya and Malan-
ville are located in that sector, the Chamber considers that it has juris-
diction to determine where the boundary is located on these bridges.
121. Niger contends that the boundary is situated at the middle point
of each of the bridges. It observes that the construction and maintenance
of these structures has been financed by the Parties on an equal basis and

that the bridges are their joint property. According to Niger, it logically
follows that the boundary is situated at the middle point of this joint
property and does not follow the boundary line in the river itself. Niger
further contends that this solution has been adopted in a substantial
number of previous and existing agreements.

122. Benin, for its part, submits that the arrangements for the con-
struction and maintenance of the bridges and any provisions on joint
ownership bear no relation to the issue of territorial sovereignty. It
further contends that a difference between the location of the boundary
on the bridges and the course of the boundary in the river beneath would

be incoherent and lead to legal inconsistencies.

123. The Chamber initially observes that the two bridges crossing the
River Niger between Gaya and Malanville were built in 1958 and 1988-
1989 respectively. They are more than 300 m in length and they connect

platforms built on each of the banks, which are used for customs and
other administrative purposes.
The Chamber further observes that there are a number of arrange-
ments in place which provide that the use and maintenance of these
bridges, of which the Parties have joint ownership, is to be financed by
them on an equal basis.

It finally observes that these agreements and arrangements do not con-
tain any provisions on territorial issues.
124. The Chamber notes that neither of the Parties has contended that
there is a rule of customary international law regarding territorial delimi-
tation in the case of bridges over international watercourses. It further

notes that the various precedents cited in the case file are all based on
bilateral agreements.
The Chamber observes that, in the absence of an agreement between

55 FRONTIER DISPUTE (JUDGMENT ) 142

the Parties, the solution is to extend vertically the line of the boundary on
the watercourse. This solution accords with the general theory that a

boundary represents the line of separation between areas of State sov-
ereignty, not only on the earth’s surface but also in the subsoil and in the
superjacent column of air. Moreover, the solution consisting of the ver-
tical extension of the boundary line on the watercourse avoids the diffi-
culties which could be engendered by having two different boundaries on

geometrical planes situated in close proximity to one another.
In light of the foregoing, the Chamber concludes that the boundary on
the bridges between Gaya and Malanville follows the course of the
boundary in the river. This finding is without prejudice to the arrange-
ments in force between Benin and Niger regarding the use and mainte-

nance of these bridges, which are financed by the two States on an equal
basis (see paragraph 123 above). The Chamber observes in particular
that the question of the course of the boundary on the bridges is totally
independent of that of the ownership of those structures, which belong to
the Parties jointly.

* * *

125. The Chamber is further charged under Article 2 (c) of the Special
Agreement with “determin[ing] the course of the boundary between the
two States in the River Mekrou sector”.

Although Benin contended that this issue was a “quite artificial dispute
created by Niger at the time of negotiation of the Special Agreement” for
tactical purposes and that until then there had never been any disagree-
ment between the Parties on the matter — an assertion which Niger
strongly denied —, there can be no doubt that the Chamber’s task,

according to the express terms of the Special Agreement, includes settle-
ment of this aspect of the dispute, without having to speculate on the
motives of either Party. Indeed Benin has not sought to argue otherwise.

**

126. The dispute between the Parties in regard to this sector of the
boundary may be summarized as follows.
According to Benin, the boundary follows the median line of the River
Mekrou. That is said to result, on the one hand, from the application of

the uti possidetis juris principle, since, at their dates of independence, the
territories of Dahomey and Niger were separated by the course of that
river pursuant both to the legal titles in force and to the effectivités ;on
the other hand and in any event, such a boundary is said to have been
confirmed by Niger’s formal recognition, at the time of the negotiations

between the two Parties in 1973 and 1974 with a view to the construction
of the Dyodyonga dam, that the Mekrou did indeed constitute the
boundary between their respective territories. In this connection, Benin

56 FRONTIER DISPUTE (JUDGMENT ) 143

relies on a Note Verbale from Niger dated 29 August 1973 and on the
minutes of a meeting held on 8 February 1974 between the experts of the

two Parties (see paragraph 39 above), the River Mekrou being indicated
in both of these documents as constituting the boundary between the two
States.
According to Niger, the boundary in the sector in question follows a
line comprising two parts: the first is a straight line joining the point of

confluence of the River Mekrou with the River Niger to the point where
the Paris meridian meets the Atakora mountain range: the second part
joins this latter point to the point where the former boundary between
the cercles of Say and Fada meets the former boundary between the
cercles of Fada and Atakora. That is claimed to result from the combined

effect of the regulatory instruments which, during the colonial period,
defined the boundary between Dahomey and Niger in the sector in ques-
tion, namely the decree of 2 March 1907 incorporating the cercles of
Fada-N’Gourma and Say into the colony of Haut-Sénégal et Niger (to
which Niger succeeded) and the decrees of 12 August 1909 and 23 April
1913 (see paragraph 39 above) modifying the boundary of the latter

colony with Dahomey. As regards the documents of 1973 and 1974 relied
on by Benin, Niger contends that, even assuming that they can be
regarded as creating a legal obligation, such obligation is vitiated by a
manifest error which would deprive it of any validity according to the
rules of customary law concerning defects in international agreements, as

codified in Article 48, paragraph 1, of the Vienna Convention on the Law
of Treaties.
Sketch-map No. 5, on page 144 below, shows the claims of the Parties
in respect of the boundary in the sector of the River Mekrou.

**

127. The Chamber will first ascertain, by application of the principle
of uti possidetis juris, what the course of the intercolonial boundary was

at the critical dates of independence in August 1960. Only then is it
required, if necessary, to consider the documents of 1973 and 1974 relied
on by Benin in order to determine whether they could validly have pro-
duced legal effects capable of affecting the course of the international
boundary as previously defined, that is to say the boundary resulting
from the uti possidetis of 1960.

*

128. To determine the course of the intercolonial boundary at the criti-
cal date it is necessary to examine first the legal titles relied on by the

Parties, with any effectivités being considered only on a confirmatory or
subsidiary basis, in accordance with the rules recalled above (see para-
graphs 47 and 77).

57FRONTIER DISPUTE (JUDGMENT ) 144

58 FRONTIER DISPUTE (JUDGMENT ) 145

129. The first text for consideration is the above-mentioned decree of
2 March 1907, the object of which was to change the course of the

boundary between the colony of Haut-Sénégal et Niger and that of
Dahomey by incorporating the cercles of Fada N’Gourma and Say, until
then part of Dahomey, into the neighbouring colony. Article 1 of that
decree provides that the new intercolonial boundary:

“is constituted, from the boundary of Togo, by the present bound-
ary of the cercle of Gourma until it reaches the Atakora mountain
range, whose summit it follows until it meets the Paris meridian,

from which point it runs in a straight line in a north-easterly direc-
tion, terminating at the confluence of the River Mekrou with the
Niger”.

130. That delimitation, which clearly does not coincide with the course
of the River Mekrou, tends to support the position of Niger. Indeed
Niger accordingly contends that the decree of 2 March 1907, as partially
amended in 1909 and 1913 (see paragraph 39 above), remained in force
until the critical dates of independence in 1960 and that it constitutes the

legal title to be relied on for purposes of applying the uti possidetis juris
principle.
131. Benin, however, challenges this position, arguing that the 1907
delimitation was implicitly superseded by the decree of 1 March 1919 cre-
ating the colony of Haute-Volta, and that from 1919 onwards not one of

the successive administrative instruments relating to the disputed sector
mentioned the line of 1907. On the contrary, every one of those instru-
ments, and in particular the arrêté of 31 August 1927, whereby the
Governor-General of the AOF fixed the boundaries of the colonies of
Haute-Volta and Niger, expressly or impliedly adopted the course of

the Mekrou as the intercolonial boundary, as is moreover confirmed by
abundant cartographic evidence.
132. The Chamber cannot accept the proposition that the decree of
1 March 1919 implicitly abrogated or amended that of 2 March 1907 in
relation to the intercolonial boundary in the sector in question.

The 1919 decree created the colony of Haute-Volta, which was consti-
tuted by detaching a certain number of cercles, including Fada N’Gourma
and Say, from Haut-Sénégal et Niger. The effect of this was that, in
the Mekrou sector, the colony of Dahomey, instead of bordering Haut-
Sénégal et Niger, now bordered the newly created Haute-Volta, so that

the boundary established in Article 1 of the 1907 decree could no longer
be considered as separating Dahomey from Haut-Sénégal et Niger.

However, there is nothing in the terms of the 1919 decree to suggest
that its authors intended to call into question the line defined as the inter-

colonial boundary in 1907. The two cercles detached from Dahomey in
1907 in order to be included in the neighbouring colony of Haut-Sénégal
et Niger were in 1919 incorporated into the new colony of Haute-Volta.

59 FRONTIER DISPUTE (JUDGMENT ) 146

Nonetheless, the boundary separating those cercles (and in particular the
cercle of Say) from Dahomey, was not moved in 1919: nothing in the

terms of the decree of 1 March 1919, nor any incompatibility between
two successive texts, leads to the conclusion that the boundary clearly
and precisely defined in 1907 was modified in 1919.
133. That does not suffice however to refute Benin’s argument with
respect to the course of the boundary in the sector concerned.

134. The Chamber is bound to note, first of all, that the 1919 decree
refers neither in its citations nor in its operative articles to the 1907
decree, and that it does not include any precise definition of the inter-
colonial boundary, as the earlier decree had done. In reality, the 1919
decree defines the territory of Haute-Volta solely by reference to thceercles

which compose it, and it is thus also by this means that it indirectly
defines the boundaries between Haute-Volta and the neighbouring colo-
nies, and in particular Dahomey. It is by the precise delimitation of the
cercles mentioned in Article 1 of the decree of 1 March 1919 — a delimi-
tation not effected by the decree itself — that, from this date, the inter-
colonial boundary could be defined. In particular, it was the delimitation

of the cercle of Say that would then enable the boundary between Haute-
Volta and Dahomey to be determined in the disputed sector. However, as
recalled above (see paragraphs 30, 47 and 71), the delimitation of the
cercles, the principal administrative subdivisions of the colonies, was at
that time, pursuant to Article 5 of the decree of 18 October 1904 reorganiz-

ing the AOF, a matter falling within the competence of the Governor-
General. It must therefore be concluded from the foregoing that, while the
1919 decree did not call into question the intercolonial boundary deter-
mined in 1907, it left unaffected the power of the Governor-General to
modify the boundary in the future by fixing the boundaries of the cercles

in question in accordance with his normal competence in that regard.
135. The Chamber notes that the arrêté of the Governor-General of
31 August 1927 defines the River Mekrou as the boundary of the cercle
of Say in the area contiguous with the colony of Dahomey.
That arrêté was adopted by the Governor-General following, and as a

consequence of, the decree of 28 December 1926 incorporating the cercle
of Say into the colony of Niger (created some years earlier). It was thus
for the Governor-General to define the boundaries between the colonies
of Haute-Volta and Niger, in the exercise of his power to define the
boundaries of the cercles: that was the purpose of the arrêté of 31 August
1927. That instrument, in the second paragraph of Article 1, defined the

boundary between the cercle of Say and Haute-Volta in the following
terms:

“In the South-West [by] a line starting approximately from the
[River] Sirba at the level of the Say parallel and terminating at the

Mekrou;
In the South-East, by the Mekrou from that point as far as its
confluence with the Niger.”

60 FRONTIER DISPUTE (JUDGMENT ) 147

Thus, by this arrêté the Governor-General clearly fixed the boundary of
the cercle of Say, and hence the intercolonial boundary, on the Mekrou.

136. It is true, and Niger has been at pains to point this out, that the
arrêté of 31 August 1927 was followed on 15 October by an erratum
amending its text retroactively by removing the reference to the course of
the Mekrou as the south-eastern boundary between the cercle of Say and
Haute-Volta. Article 1 of the arrêté, as amended pursuant to the erratum

of 15 October, confines itself to stating that the boundary between the
Niger and Haute-Volta “follows . . . the course of the Tapoa upstream
until it meets the former boundary between the cercles of Fada and Say,
which it follows as far as its intersection with the course of the Mekrou”.
However, the erratum would seem in effect to have been motivated

not by the fact that the Governor-General did not mean to fix the south-
eastern boundary of the cercle of Say along the Mekrou, but rather by a
wish not to define the boundary between Dahomey and Niger in anarrêté
whose purpose, as was clear from its title, was to fix the boundary
between Niger and Haute-Volta. Not only did theerratum thus not contra-
dict the fact that the boundaries of the cercle of Say were as indicated the

previous August, but it expressly confirmed that the terminal point of the
southern boundary of that cercle was situated on the Mekrou.
137. Furthermore, the Chamber must take account of the instruments
concerning the creation of game reserves and national parks in the area
known as “The Niger W”. Both the Governor-General’s arrêté of 16 April

1926 and the arrêtés of 30 September 1937 of the Governor of Dahomey
and of 13 November of the same year of the Governor of Niger — defin-
ing within the territory of each of the two colonies the provisional extent
of their nature reserves — as well as the Governor-General’s arrêtés of
3 December 1952 and 25 June 1953 definitively fixing the borders of those

reserves, use the River Mekrou for purposes of delimitation of the areas
in question. If, in the eyes of the administrative authorities competent to
promulgate the arrêtés in question, the Mekrou did not represent the
intercolonial boundary, it is difficult to see why it should have been
chosen as the boundary of these national parks and nature reserves.

138. Finally, the Chamber is bound to note that the cartographic
material in the file clearly confirms that, certainly from 1926-1927, the
Mekrou was generally regarded as the intercolonial boundary by all the
administrative authorities and institutions of the colonial Power.

Certainly, maps — unless they are annexed to an administrative instru-

ment, and hence form an integral part thereof, which is not the case
here — possess only the relative force conferred upon them by the juris-
prudence recalled above (see paragraph 44). However, in the present case
the cartographic evidence may be regarded as confirming and reinforcing
the conclusions flowing from an analysis of the above-mentioned regula-

tive texts. The same applies notably to the map prepared and published
in October 1926 by the AOF Geographical Service (known as the “Blon-
del la Rougery map”), to the map entitled “New Boundary of Haute-

61 FRONTIER DISPUTE (JUDGMENT ) 148

Volta and Niger (according to the erratum of 5 October 1927 to the
arrêté of 31 August 1927)” and to the Dahomey-Togo roadmap prepared

by the AOF Geographical Service in 1938 (see paragraph 42 above).
139. All of the foregoing considerations confirm the position that the
1907 line no longer corresponded, at the critical date, to the intercolonial
boundary and that, on the contrary, at that date, it was the course of
the Mekrou which, in the view of all the competent authorities of the

colonial administration, constituted the boundary between the adjacent
colonies — at that date the colonies of Dahomey and Niger.
140. The Chamber observes that, as argued by Niger, the decree of
2 March 1907, which clearly defined a different boundary, was never
expressly abrogated or amended, or indeed superseded by some other

instrument of at least equal authority — either a decree or a statute —
containing provisions clearly incompatible with its own. Nor indeed was
any instrument of this kind cited by Benin in reply to a question from the
Chamber on this aspect of the dispute, with the exception of the
1919 decree, which, as explained above, did not have the abrogating
effect claimed for it by Benin.

However, further to what has already been said (see paragraph 134) in
regard to the power of the Governor-General to fix the boundaries of the
cercles and, hence, to determine those of colonies, the Chamber would
emphasize that the uti possidetis juris principle requires not only that reli-

ance be placed on existing legal titles, but also that account be taken of
the manner in which those titles were interpreted and applied by the com-
petent public authorities of the colonial Power, in particular in the exer-
cise of their law-making power. The Chamber is bound to note that the
administrative instruments promulgated after 1927 were never the subject

of any challenge before the competent courts, and that there is no evi-
dence that the colonial administration was ever criticized at the time for
having improperly departed from the line resulting from the 1907 decree.
It is not for the Chamber to substitute itself for a domestic court (in this
case, the French administrative courts) by carrying out its own review of

the legality of the instruments in question in light of the 1907 decree, nor
to speculate on what the French courts might have decided had they been
seised of the matter. The fact is that they were not so seised and that
there is nothing to suggest that, in the decisions taken by them after 1927,
the administrative authorities either manifestly exceeded their powers or
acted in manifest breach of the applicable rules.

*

141. It follows from all of the foregoing that, at least from 1927
onwards, the competent administrative authorities regarded the course of

the Mekrou as the intercolonial boundary separating Dahomey from
Niger, that those authorities reflected that boundary in the successive
instruments promulgated by them after 1927, some of which expressly

62 FRONTIER DISPUTE (JUDGMENT ) 149

indicated that boundary, whilst others necessarily implied it, and that this
was the state of the law at the dates of independence in August 1960.

In these circumstances, it is unnecessary to look for any effectivités in
order to apply the uti possidetis principle, since effectivités can only be of
interest in a case in order to complete or make good doubtful or absent
legal titles, but can never prevail over titles with which they are at vari-
ance. The Chamber notes moreover, ex abundanti, that the effectivités

relied on by the Parties in the sector in question are relatively weak.

**

142. In the light of the preceding conclusion, the dispute between the
Parties regarding the legal effect of Niger’s Note Verbale of 29 August
1973 and of the minutes of the meeting of experts of 8 February 1974

becomes moot. It is thus unnecessary to decide whether those documents
could have constituted a legally binding obligation for Niger and, if so,
whether that obligation could have been vitiated by an error fulfilling the
conditions laid down by customary international law.

**

143. Lastly, it remains for the Chamber to determine the exact loca-
tion in the River Mekrou of the boundary between Benin and Niger. In
this respect, in its final submissions Benin requested the Chamber to
adjudge and declare that, in this sector, the boundary follows “the
median line of the River Mekrou”. Niger did not expressly adopt a posi-

tion on this question, even on an alternative basis; it did, however, con-
tend in its written pleadings that the eastern starting point of the bound-
ary in that sector (corresponding to the western terminal point of the
boundary in the River Niger sector) is constituted by the “confluence of
the River Niger with the Mekrou”, which it locates at “the intersection of

the thalweg of the River Mekrou with the main channel of the River
Niger” or at the “point of intersection of the axes of the River Niger and
the River Mekrou”.
144. The Chamber would recall that, in the case concerning Kasikili/
Sedudu Island (Botswana/Namibia) , the Court observed that:

“Treaties or conventions which define boundaries in watercourses
nowadays usually refer to the thalweg as the boundary when the
watercourse is navigable and to the median line between the two

banks when it is not, although it cannot be said that practice has
been fully consistent.” (I.C.J. Reports 1999 (II) , p. 1062, para. 24.)

In the present case, the Chamber notes that, during a reconnaissance
mission carried out in April 1998, the joint technical committee of the
Joint Benin-Niger Boundary Delimitation Commission

63 FRONTIER DISPUTE (JUDGMENT ) 150

“plotted the co-ordinates of the point of intersection of the axes of
the River Niger and River Mekrou, but was not able to continue its
work beyond that point because navigation on the River Mekrou

[was] not possible due to the low water level”.
Moreover, the Parties did not provide the Chamber with any docu-

ments that would enable the exact course of the thalweg of the Mekrou
to be identified. The Chamber notes that in all likelihood there is a neg-
ligible difference between the course of the thalweg and the course of the
median line of the River Mekrou, but considers that, in view of the cir-

cumstances, including the fact that the river is not navigable, a boundary
following the median line of the Mekrou would more satisfactorily meet
the requirement of legal security inherent in the determination of an
international boundary.
145. The Chamber concludes, for the foregoing reasons, that, in the

sector of the River Mekrou, the boundary between Benin and Niger is
constituted by the median line of that river.

*
* *
146. For these reasons,

T HE C HAMBER ,

(1) By four votes to one,

Finds that the boundary between the Republic of Benin and the
Republic of Niger in the River Niger sector takes the following course:

— the line of deepest soundings of the main navigable channel of that
river, from the intersection of the said line with the median line of the
River Mekrou until the point situated at co-ordinates 11°52′29″ lati-

tude North and 3°25′34″ longitude East;
— from that point, the line of deepest soundings of the left navigable
channel until the point located at co-ordinates 11°51′55″ latitude
North and 3°27′41″ longitude East, where the boundary deviates

from this channel and passes to the left of the island of Kata Goungou,
subsequently rejoining the main navigable channel at the point located
at co-ordinates 11°51′41″ latitude North and 3°28′53″ longitude
East;

— from this latter point, the line of deepest soundings of the main navi-
gable channel of the river as far as the boundary of the Parties with
Nigeria;

and that the boundary line, proceeding downstream, passes through the
points numbered from 1 to 154, the co-ordinates of which are indicated
in paragraph 115 of the present Judgment;

IN FAVOUR : Judge Ranjeva, Vice-President of the Court, President of the
Chamber; Judges Kooijmans, Abraham; Judge ad hoc Bedjaoui;
AGAINST: Judge ad hoc Bennouna;

64 FRONTIER DISPUTE (JUDGMENT ) 151

(2) By four votes to one,

Finds that the islands situated in the River Niger therefore belong to
the Republic of Benin or to the Republic of Niger as indicated in para-

graph 117 of the present Judgment;
IN FAVOUR : Judge Ranjeva, Vice-President of the Court, President of the
Chamber; Judges Kooijmans, Abraham; Judge ad hoc Bedjaoui;

AGAINST : Judge ad hoc Bennouna;

(3) By four votes to one,

Finds that the boundary between the Republic of Benin and the
Republic of Niger on the bridges between Gaya and Malanville follows
the course of the boundary in the river;

IN FAVOUR : Judge Ranjeva, Vice-President of the Court, President of the
Chamber; Judges Kooijmans, Abraham; Judge ad hoc Bedjaoui;
AGAINST : Judge ad hoc Bennouna;

(4) Unanimously,

Finds that the boundary between the Republic of Benin and the
Republic of Niger in the River Mekrou sector follows the median line of
that river, from the intersection of the said line with the line of deepest

soundings of the main navigable channel of the River Niger as far as the
boundary of the Parties with Burkina Faso.

Done in French and in English, the French text being authoritative, at
the Peace Palace, The Hague, this twelfth day of July, two thousand and
five, in three copies, one of which will be placed in the archives of the
Court and the others transmitted to the Government of the Republic of

Benin and the Government of the Republic of Niger, respectively.

(Signed) President of the Chamber.(Signed) Raymond R ANJEVA ,

President of the Chamber.

(Signed) Philippe C OUVREUR ,
Registrar.

Judge ad hoc B ENNOUNA appends a dissenting opinion to the Judgment
of the Chamber.

(Initialled) R.R.

(Initialled) Ph.C.

65

Bilingual Content

COUR INTERNATIONALE DE JUSTICE

RECUEIL DES AR|TS,
AVIS CONSULTATIFS ET ORDONNANCES

AFFAIRE

DU DIFFE uREND FRONTALIER
(BuNIN/NIGER)

ARR|T DU 12 JUILLET 2005

2005

INTERNATIONAL COURT OF JUSTICE

REPORTS OF JUDGMENTS,
ADVISORY OPINIONS AND ORDERS

CASE CONCERNING

THE FRONTIER DISPUTE
(BENIN/NIGER)

JUDGMENT OF 12 JULY 2005 Mode officiel de citation:
Différend frontalier (Bénin/Niger),
arrêt, C.I.J. Recueil 2005 ,p.90

Official citation:
Frontier Dispute (Benin/Niger),
Judgment, I.C.J. Reports 2005 ,p.90

o
N de vente:
ISSN 0074-4441 Sales number 902
ISBN 92-1-071012-6 12 JUILLET 2005

ARRE|T

DIFFuREND FRONTALIER

(BuNIN/NIGER)

FRONTIER DISPUTE

(BENIN/NIGER)

12 JULY 2005

JUDGMENT 90

COUR INTERNATIONALE DE JUSTICE

2005 ANNÉE 2005
12 juillet
Rôleogénéral
n 125 12 juillet 2005

AFFAIRE

DU DIFFE uREND FRONTALIER

(BuNIN/NIGER)

Cadre géographique — Contexte historique.

Droit applicable — Principe de l’ uti possidetis juris — Tracé de la frontière
devant être établi par référence à la situation physique à laquelle le droit colo-
nial français s’est appliqué, telle qu’elle existait à la date des indépendances
— Conséquences de ce tracé sur le terrain devant s’apprécier par rapport aux
réalités physiques contemporaines — Prise en considération des documents et
cartes postérieurs à la date des indépendances dans le cadre de l’application du
principe de l’uti possidetis juris — Valeur juridique des effectivités postcolo-
niales.
Place du droit colonial (droit français d’outre-mer) — Compétences des
autorités coloniales pour la création et la suppression de colonies et de subdivi-
sions territoriales.
Evolution du statut juridique des territoires en cause.
Principaux documents pertinents aux fins du règlement du différend.
Matériau cartographique — Valeur probante des cartes.

**

Tracé de la frontière dans le secteur du fleuve Niger et appartenance des îles
du fleuve à l’une ou l’autre des Parties.
Examen des actes réglementaires et administratifs invoqués par les Parties.
Arrêté du 23 juillet 1900 du gouverneur général de l’AOF et décret du
20 décembre 1900 du président de la République française ne fixant pas les
limites du troisième territoire militaire — Arrêté de 1900 n’ayant pas situé la
limite intercoloniale sur la rive gauche du fleuve Niger — Lettre en date du
27 août 1954 de M. Raynier, gouverneur par intérim du Niger — Contexte
de cette lettre — Lettre ne pouvant pas être considérée comme une confir-
mation autorisée d’une limite préétablie — Prétention du Bénin selon laquelle
ladite lettre constituerait, avec l’arrêté du 23 juillet 1900, un titre juridique
à l’appui de ses thèses ne pouvant être accueillie.

4 90

INTERNATIONAL COURT OF JUSTICE

YEAR 2005 2005
12 July
12 July 2005 General List
No. 125

CASE CONCERNING
THE FRONTIER DISPUTE

(BENIN/NIGER)

Geographical context — Historical background.
Applicable law — Principle of uti possidetis juris — Course of the boundary
to be determined by reference to the physical situation to which French colonial
law was applied, as that situation existed at the dates of independence — Con-
sequences of that course on the ground to be assessed in relation to present-day
physical realities — Relevance of documents and maps posterior to dates of
independence for purposes of applying the uti possidetis juris principle — Legal
value of post-colonial effectivités.

Place of colonial law (French droit d’outre-mer) — Powers of colonial

authorities to create and abolish colonies and territorial subdivisions .

Evolution of legal status of territories concerned .
Principal documents relevant to the settlement of the dispute .
Cartographic materials — Value of maps as evidence.

**

Course of boundary in River Niger sector and the question of to which Party
the islands in the river belong.
Examination of regulative and administrative acts invoked by the Parties .
Arrêté of 23 July 1900 of the Governor-General of French West Africa
(AOF) and decree of 20 December 1900 of the President of the French Repub-
lic did not fix the boundaries of the third military territory — Arrêté of 1900 did
not locate the intercolonial boundary on the left bank of the River Niger — Let-
ter of 27 August 1954 from Mr. Raynier, Governor ad interim of Niger — Con-
text of that letter — Letter cannot be seen as authoritative confirmation of a
previously established boundary — Benin’s contention that the said letter, in
conjunction with the decree of 23 July 1900, constitutes a legal title substanti-
ating its claims cannot be upheld.

491 DIFFÉREND FRONTALIER (ARRÊT )

Arrêtés des 8 décembre 1934 et 27 octobre 1938 du gouverneur général de
l’AOF — Arrêtés n’ayant pas situé la limite intercoloniale dans le fleuve — Pré-

tention du Niger selon laquelle lesdits arrêtés constitueraient un titre juridique à
l’appui de ses thèses ne pouvant être accueillie.
Absence de preuve de l’existence d’un titre fixant la limite à l’époque coloniale
— Rapport juridique entre titre et effectivités.
Examen des effectivités invoquées par les Parties — Effectivités antérieures à
1954 — Lettre de l’administrateur adjoint Sadoux en date du 3 juillet 1914 et
modus vivendi — Termes du modus vivendi ayant été dans l’ensemble respectés
jusqu’en 1954 — Ile de Lété ayant été administrée par le Niger — Iles situées en
face de Gaya ayant été administrées par le Dahomey — Situation moins claire
entre 1954 et la date critique — Administration de l’île de Lété n’ayant pas été
transférée au Dahomey ou reprise par celui-ci durant cette période.
Frontière entre les Parties suivant le chenal navigable principal du fleuve

Niger tel qu’il existait à la date des indépendances et passant à gauche des trois
îles situées en face de Gaya — Répartition des îles du fleuve suivant cette
frontière.

*

Emplacement précis de la ligne frontière dans le chenal navigable principal
— Ligne des sondages les plus profonds telle qu’elle existait à la date des indé-
pendances.
Levés hydrographiques et topographiques effectués sur le fleuve au fil des ans
— Lit du fleuve étant relativement stable — Rapport produit en 1970 par
l’entreprise NEDECO constituant la source de renseignements la plus utile sur
la situation existant à la date critique — Frontière entre les Parties suivant la
ligne des sondages les plus profonds du chenal navigable principal du fleuve
Niger telle qu’elle résulte de ce rapport, et étant constituée, face à Gaya, par la

ligne des sondages les plus profonds du chenal navigable gauche, sauf au niveau
de l’île de Kata Goungou, où elle passe à gauche de l’île — Coordonnées des
points par lesquels passe la frontière.
Détermination de l’appartenance de chacune des îles du fleuve au Bénin ou au
Niger — Réserve concernant les droits privés détenus sur les îles.

*

Tracé de la frontière sur les ponts reliant Gaya et Malanville — Compétence
de la Chambre pour déterminer ce tracé — Frontière sur ces ponts suivant le
tracé de la frontière dans le fleuve.

**
Tracé de la frontière dans le secteur de la rivière Mékrou.
Examen des documents invoqués par les Parties — Décret du 2 mars 1907
ayant procédé à une délimitation dans ce secteur — Décret du 1 er mars 1919
constitutif de la colonie de la Haute-Volta n’ayant pas implicitement abrogé ou
modifié le décret de 1907 — Arrêté du 31 août 1927 et erratum du 15 octobre

1927 définissant la limite entre les colonies de la Haute-Volta et du Niger
— Textes relatifs à la création de réserves de chasse et de parcs nationaux dans
la région «du W du Niger».
Matériau cartographique.

5 FRONTIER DISPUTE (JUDGMENT ) 91

Arrêtés of 8 December 1934 and 27 October 1938 of the Governor-General of
the AOF — Did not locate the intercolonial boundary in the river — Niger’s
contention that said arrêtés constitute a legal title substantiating its claims can-
not be upheld.
No evidence of existence of a title determining the boundary in the colonial

period — Legal relationship between title and effectivités.
Consideration of effectivités relied on by the Parties — Effectivités prior to
1954 — Letter from administrateur adjoint Sadoux of 3 July 1914 and modus
vivendi — Terms of modus vivendi generally respected until 1954 — Island of
Lété administered by Niger — Islands opposite Gaya administered by Daho-
mey — Situation less clear between 1954 and critical date — Administration of
island of Lété not transferred to or taken over by Dahomey during this period.

Boundary between the Parties follows the main navigable channel of the River
Niger as it existed at the dates of independence and passes to the left of the
three islands opposite Gaya — Attribution of islands in the river according to
this boundary.

*
Precise location of boundary line in the main navigable channel — Line of
deepest soundings as it existed at the dates of independence.

Hydrographic and topographic surveys of the river over the course of time —
Riverbed relatively stable — NEDECO report of 1970 the most useful source of
information on the situation at the critical date — Boundary between the
Parties follows the line of deepest soundings of the main navigable channel of
the River Niger as it appears in that report and to be constituted opposite Gaya
by the line of deepest soundings of the left navigable channel, except in the vicin-
ity of the island of Kata Goungou, where it passes to the left of that island —
Co-ordinates of the points through which the boundary passes .

Determination of which of the islands in the river belong to Benin and which
to Niger — Determination without prejudice to private law rights in respect of
the islands.

*
Course of the boundary on the bridges between Gaya and Malanville —
Chamber’s jurisdiction to determine that boundary — Boundary on the bridges
to follow the course of the boundary in the river.

**
Course of the boundary in the River Mekrou sector .
Consideration of the documents relied on by the Parties — Decree of 2 March

1907 effected a delimitation in this sector — Decree of 1 March 1919 creating
the colony of Haute-Volta did not implicitly abrogate or amend the decree of
1907 — Arrêté of 31 August 1927 and erratum of 15 October 1927 defining the
boundary between the colonies of Haute-Volta and Niger — Instruments con-
cerning the creation of game reserves and national parks in the “Niger W” area .

Cartographic materials.

592 DIFFÉREND FRONTALIER (ARRÊT )

Ligne définie en 1907 ne correspondant plus à la limite intercoloniale à la date
critique — Décret de 1907 n’ayant été ni expressément abrogé ou modifié ni
supplanté par un autre texte — Compétence du gouverneur général de l’AOF
pour fixer les limites des cercles et, partant, pour préciser celles des colonies
dans le cas où les limites d’un cercle sont aussi celles d’une colonie — Principe

de l’uti possidetis juris impliquant la prise en considération de la manière dont
les titres étaient interprétés et appliqués par les autorités publiques compétentes
de la puissance coloniale — Rivière Mékrou considérée comme la limite inter-
coloniale à la date critique.
Frontière entre les Parties étant constituée par la ligne médiane de la rivière
Mékrou.

ARRÊT

Présents: M. R ANJEVA, vice-président de la Cour, président de la Chambre ;
MM. K OOIJMANS,A BRAHAM , juges; MM. B EDJAOUI ,B ENNOUNA ,

juges ad hoc; M. C OUVREUR , greffier.

En l’affaire du différend frontalier,

entre

la République du Bénin,
représentée par
S. Exc. M. Rogatien Biaou, ministre des affaires étrangères et de l’intégration

africaine,
comme agent;

S. Exc. M. Dorothé C. Sossa, garde des sceaux, ministre de la justice, de la
législation et des droits de l’homme,
comme coagent;

S. Exc. M. Euloge Hinvi, ambassadeur de la République du Bénin auprès des
pays du Benelux,
comme agent adjoint;
e
M Robert Dossou, avocat au barreau du Bénin, ancien bâtonnier, doyen
honoraire de la faculté de droit de l’Université d’Abomey-Calavi,
M. Alain Pellet, professeur de droit à l’Université de Paris X-Nanterre,
membre et ancien président de la Commission du droit international,
M. Jean-Marc Thouvenin, professeur de droit à l’Université de Paris X-
Nanterre, avocat au barreau de Paris, associé du cabinet Lysias,
M. Mathias Forteau, professeur de droit à l’Université Lille 2 et à l’Institut

d’études politiques de Lille,
comme conseils et avocats;

M. Francis Lokossa, directeur des affaires juridiques et des droits de l’homme
du ministère des affaires étrangères et de l’intégration africaine,
comme conseiller spécial;

6 FRONTIER DISPUTE (JUDGMENT ) 92

Line of 1907 no longer corresponded to the intercolonial boundary at the
critical date — Decree of 1907 was never expressly abrogated or amended or
superseded by another text — Power of the Governor-General of AOF to fix the
boundaries of cercles and, hence, to determine those of colonies where the
boundaries of a cercle are also those of a colony — Uti possidetis juris principle

requires that account be taken of the manner in which titles were interpreted and
applied by the competent public authorities of the colonial Power — River
Mekrou regarded as intercolonial boundary at the critical date .

Boundary between the Parties constituted by the median line of the River
Mekrou.

JUDGMENT

Present: Judge R ANJEVA, Vice-President of the Court, President of the
Chamber; Judges K OOIJMANS,A BRAHAM ; Judges ad hoc B EDJAOUI,

BENNOUNA ; Registrar OUVREUR .

In the case concerning the frontier dispute,

between

the Republic of Benin,
represented by
H.E. Mr. Rogatien Biaou, Minister for Foreign Affairs and African Integra-

tion,
as Agent;

H.E. Mr. Dorothé C. Sossa, Keeper of the Seals, Minister of Justice, Legisla-
tion and Human Rights,
as Co-Agent;

H.E. Mr. Euloge Hinvi, Ambassador of the Republic of Benin to the Benelux
countries,
as Deputy Agent;

Maître Robert Dossou, Avocat at the Benin bar, former Bâtonnier, Honor-
ary Dean of the Law Faculty, University of Abomey-Calavi,
Mr. Alain Pellet, Professor of Law, University of Paris X-Nanterre, member
and former Chairman of the International Law Commission,
Mr. Jean-Marc Thouvenin, Professor of Law, University of Paris X-Nan-
terre, Avocat at the Paris Bar, partner in the Lysias law firm,
Mr. Mathias Forteau, Professor of Law at the University of Lille 2 and at

the Lille Institute of Political Studies,
as Counsel and Advocates;

Mr. Francis Lokossa, Director of Legal Affairs and Human Rights, Ministry
of Foreign Affairs and African Integration,
as Special Adviser;

693 DIFFÉREND FRONTALIER (ARRÊT )

M. François Noudegbessi, secrétaire permanent de la commission nationale
de délimitation des frontières,
M. Jean-Baptiste Monkotan, conseiller juridique du président de la Répu-
blique du Bénin,
M. Honoré D. Koukoui, secrétaire général du ministère de la justice, de la

législation et des droits de l’homme,
M. Jacques Migan, avocat au barreau de Cotonou, conseiller juridique du
président de la République du Bénin,
M me Héloïse Bajer-Pellet, avocat au barreau de Paris, cabinet Lysias,
M. Luke Vidal, juriste, cabinet Lysias,
M. Daniel Müller, juriste, chercheur au Centre de droit international de
Nanterre (CEDIN),
M me Christine Terriat, juriste, cabinet de M Robert M. Dossou,
e
M. Maxime Jean-Claude Hounyovi, économiste, cabinet de M Robert M.
Dossou,
M. Edouard Roko, premier secrétaire de l’ambassade de la République du
Bénin auprès des pays du Benelux,
comme conseillers;

M. Pascal Lokovi, expert cartographe,
M. Clément C. Vodouhe, expert historien,

comme conseils et experts;
M me Collette Tossouko, secrétaire à l’ambassade de la République du Bénin
auprès des pays du Benelux,

comme secrétaire,
et

la République du Niger,
représentée par

S. Exc. M me Aïchatou Mindaoudou, ministre des affaires étrangères, de la
coopération et de l’intégration africaine,

comme agent;
S. Exc. M. Maty El Hadji Moussa, ministre de la justice, garde des sceaux,
comme coagent;

S. Exc. M. Souley Hassane, ministre de la défense nationale;
S. Exc. M. Mounkaïla Mody, ministre de l’intérieur et de la décentralisation;
M. Boukar Ary Maï Tanimoune, directeur des affaires juridiques et du
contentieux au ministère des affaires étrangères, de la coopération et de
l’intégration africaine,

comme agent adjoint, conseiller juridique et coordonnateur;
M. Jean Salmon, professeur émérite de l’Université libre de Bruxelles,

comme conseil principal;
M. Maurice Kamto, professeur à l’Université de Yaoundé II,
M. Gérard Niyungeko, professeur et ancien vice-recteur à l’Université du
Burundi, ancien président de la Cour constitutionnelle du Burundi,

M. Amadou Tankoano, professeur à l’Université Abdou Moumouni de Niamey,
M. Pierre Klein, professeur à l’Université libre de Bruxelles,
comme conseils;

7 FRONTIER DISPUTE (JUDGMENT ) 93

Mr. François Noudegbessi, Permanent Secretary, National Commission for
the Delimitation of Boundaries,
Mr. Jean-Baptiste Monkotan, Legal Adviser to the President of the Republic
of Benin,
Mr. Honoré D. Koukoui, Secretary General, Ministry of Justice, Legislation

and Human Rights,
Mr. Jacques Migan, Avocat at the Cotonou Bar, Legal Adviser to the Presi-
dent of the Republic of Benin,
Ms Héloïse Bajer-Pellet, Avocat at the Paris Bar, Lysias law firm,
Mr. Luke Vidal, lawyer, Lysias law firm,
Mr. Daniel Müller, lawyer, Researcher at the Centre de droit international
de Nanterre (CEDIN),
Ms Christine Terriat, lawyer, Maître Robert M. Dossou law firm,
Mr. Maxime Jean-Claude Hounyovi, Economist, Maître Robert M. Dossou
law firm,
Mr. Edouard Roko, First Secretary, Embassy of the Republic of Benin to
the Benelux countries,

as Advisers;
Mr. Pascal Lokovi, Cartographer,

Mr. Clément C. Vodouhe, Historian,
as Counsel and Experts;
Ms Collette Tossouko, Secretarial Assistant, Embassy of the Republic of
Benin to the Benelux countries,

as Secretary,
and

the Republic of Niger,
represented by

H.E. Ms Aïchatou Mindaoudou, Minister for Foreign Affairs, Co-operation
and African Integration,
as Agent;

H.E. Mr. Maty El Hadji Moussa, Minister of Justice, Keeper of the Seals,
as Co-Agent;
H.E. Mr. Souley Hassane, Minister of National Defence;
H.E. Mr. Mounkaïla Mody, Minister of the Interior and Decentralization;

Mr. Boukar Ary Maï Tanimoune, Director of Legal Affairs and Litigation,
Ministry of Foreign Affairs, Co-operation and African Integration,

as Deputy Agent, Legal Adviser and Co-ordinator;

Mr. Jean Salmon, Professor Emeritus, Université libre de Bruxelles,
as Lead Counsel;
Mr. Maurice Kamto, Professor, University of Yaoundé II,
Mr. Gérard Niyungeko, Professor and former Vice-Recteur, University of
Burundi, former President of the Constitutional Court of Burundi,

Mr. Amadou Tankoano, Professor, Abdou Moumouni University, Niamey,
Mr. Pierre Klein, Professor, Université libre de Bruxelles,
as Counsel;

794 DIFFÉREND FRONTALIER (ARRÊT )

M. Sadé Elhadji Mahamane, conservateur en chef des bibliothèques et
archives, membre de la commission nationale des frontières,
M. Amadou Maouli Laminou, magistrat, chef de section au ministère de la

justice,
S. Exc. M. Abdou Abarry, ambassadeur de la République du Niger auprès
du Royaume des Pays-Bas,
M. Abdelkader Dodo, hydrogéologue, maître assistant à la faculté des
sciences de l’Université Abdou Moumouni de Niamey,
M. Belko Garba, ingénieur géomètre principal, membre de la commission
nationale des frontières,
M. M. Hamadou Mounkaïla, ingénieur géomètre principal, chef de service

au secrétariat permanent de la commission nationale des frontières,
M. Idrissa Y Maïga, conservateur en chef des bibliothèques et archives, directeur
des archives nationales, membre de la commission nationale des frontières,
M. Mahaman Laminou, directeur général de l’Institut géographique national
du Niger, membre de la commission nationale des frontières,
M. Mahamane Koraou, secrétaire permanent de la commission nationale des
frontières,

M. Soumaye Poutia, magistrat, conseiller technique au cabinet du premier
ministre,
Colonel Yayé Garba, secrétaire général du ministère de la défense nationale,
M. Moutari Laouali, gouverneur de la région de Dosso,
comme experts;

M. Emmanuel Klimis, assistant de recherche au centre de droit international
de l’Université libre de Bruxelles,
M. Boureima Diambeïdou, ingénieur géomètre principal,
M. Bachir Hamissou, assistant administratif,

M. Ouba Adamou, ingénieur géomètre principal, Institut géographique natio-
nal du Niger,
comme assistants de recherche;

M. Salissou Mahamane, agent comptable,
M. Adboulsalam Nouri, secrétaire principal,
M me Haoua Ibrahim, secrétaire,
M. Amadou Gagéré, agent administratif,
M. Amadou Tahirou, agent administratif,
M. Mamane Chamsou Maïgari, journaliste, directeur de la Voix du Sahel,

M. Goussama Saley Madougou, cameraman à la télévision nationale,
M. Ali Moussa, journaliste à l’agence nigérienne de presse,
M. Issoufou Guéro, journaliste,
comme personnel administratif et technique,

L A C HAMBRE DE LA C OUR INTERNATIONALE DE JUSTICE constituée pour
connaître de l’affaire susmentionnée,

ainsi composée,
après délibéré en chambre du conseil,

rend l’arrêt suivant:

1. Par une lettre de notification conjointe datée du 11 avril 2002 et déposée
au Greffe de la Cour le 3 mai 2002, la République du Bénin (dénommée ci-

8 FRONTIER DISPUTE JUDGMENT ) 94

Mr. Sadé Elhadji Mahamane, Chief Curator of Libraries and Archives,
member of the National Boundaries Commission,
Mr. Amadou Maouli Laminou, Magistrat, Head of Section at the Ministry
of Justice,
H.E. Mr. Abdou Abarry, Ambassador of the Republic of Niger to the King-
dom of the Netherlands,
Mr. Abdelkader Dodo, Hydro-geologist, Lecturer at the Faculty of Sciences,

Abdou Moumouni University, Niamey,
Mr. Belko Garba, Chief Surveyor, member of the National Boundaries
Commission,
Mr. M. Hamadou Mounkaïla, Chief Surveyor, Head of Department, Perma-
nent Secretariat of the National Boundaries Commission,
Mr. Idrissa Y Maïga, Chief Curator of Libraries and Archives, Director of
National Archives, member of the National Boundaries Commission,
Mr. Mahaman Laminou, Director-General of the National Geographical
Institute of Niger, member of the National Boundaries Commission,

Mr. Mahamane Koraou, Permanent Secretary to the National Boundaries
Commission,
Mr. Soumaye Poutia, Magistrat, Technical Adviser to the Office of the Prime
Minister,
Colonel Yayé Garba, Secretary General of the Ministry for National Defence,
Mr. Moutari Laouali, Governor of the Region of Dosso,

as Experts;
Mr. Emmanuel Klimis, Research Assistant at the Centre for International
Law, Université libre de Bruxelles,
Mr. Boureima Diambeïdou, Chief Surveyor,
Mr. Bachir Hamissou, Administrative Assistant,

Mr. Ouba Adamou, Chief Surveyor, National Geographic Institute of
Niger,
as Research Assistants;

Mr. Salissou Mahamane, Accountant,
Mr. Adboulsalam Nouri, Principal Secretary,
Ms Haoua Ibrahim, Secretary,
Mr. Amadou Gagéré, Administrative Officer,
Mr. Amadou Tahirou, Administrative Officer,
Mr. Mamane Chamsou Maïgari, journalist, Director of Voix du Sahel,
Mr. Goussama Saley Madougou, cameraman for national television,
Mr. Ali Moussa, journalist with the Niger Press Agency,

Mr. Issoufou Guéro, journalist,
as Administrative and Technical Staff,

T HE CHAMBER OF THE INTERNATIONAL C OURT OF JUSTICEformed to deal with
the above-mentioned case,

composed as above,

after deliberation,
delivers the following Judgment:

1. By a joint letter of notification dated 11 April 2002, filed in the Registry of
the Court on 3 May 2002, the Republic of Benin (hereinafter “Benin”) and the

895 DIFFÉREND FRONTALIER (ARRÊT )

après le «Bénin») et la République du Niger (dénommée ci-après le «Niger»)
ont fait tenir au greffier une copie certifiée conforme d’un compromis signé à

Cotonou le 15 juin 2001 et entré en vigueur le 11 avril 2002, par lequel les gou-
vernements de ces deux Etats sont convenus de soumettre à une chambre de la
Cour un différend concernant «la délimitation définitive de l’ensemble de leur
frontière».
2. Le texte du compromis du 15 juin 2001 est le suivant:
«Le Gouvernement de la République du Bénin et le Gouvernement de la
République du Niger, ci-après dénommés les «Parties»;

Considérant que, par l’accord signé le 8 avril 1994, entré provisoirement
en vigueur à la date de sa signature, ratifié respectivement par le Bénin le
17 juillet 1997 et par le Niger le 1 février 2001, et entré définitivement en
vigueur le 15 juin 2001, date d’échange des instruments de ratification, les
deux gouvernements ont procédé à la création de la commission mixte
paritaire de délimitation de leur frontière;

Considérant qu’en dépit de six sessions de négociations au sein de ladite
commission, les experts des deux Etats ne sont pas parvenus à se mettre
d’accord sur le tracé de la frontière commune;
Considérant que selon l’article 15 de l’accord du 8 avril 1994 précité,

«les Parties contractantes conviennent de soumettre tous différends ou
litiges nés de l’application ou de l’interprétation du présent accord à un
règlement par voie diplomatique, ou aux autres modes de règlement
pacifique prévus par les Chartes de l’Organisation de l’unité africaine et
de l’Organisation des Nations Unies»;
Désireux de parvenir dans les meilleurs délais au règlement du différend

frontalier qui les oppose en se fondant sur les dispositions de la Charte
ainsi que sur les résolutions de l’Organisation de l’unité africaine et de
soumettre la question de la délimitation définitive de l’ensemble de leur
frontière à la Cour internationale de Justice, ci-après dénommée «la
Cour»;
Sont convenus de ce qui suit:

Article premier
Constitution d’une chambre de la Cour internationale de Justice
1. Les Parties soumettent le différend défini à l’article 2 ci-dessous à une
chambre de la Cour, ci-après désignée «la Chambre», constituée confor-

mément aux dispositions du Statut de la Cour et du présent compromis.
2. Chacune des Parties exercera le droit que lui confère le paragraphe 3
de l’article 31 du Statut de la Cour de procéder à la désignation d’un juge
ad hoc.
Article 2

Objet du différend
La Cour est priée de:
a) déterminer le tracé de la frontière entre la République du Bénin et la
République du Niger dans le secteur du fleuve Niger;

b) préciser à quel Etat appartient chacune des îles dudit fleuve et en par-
ticulier l’île de Lété;
c) déterminer le tracé de la frontière entre les deux Etats dans le secteur
de la rivière Mékrou.

9 FRONTIER DISPUTE (JUDGMENT ) 95

Republic of Niger (hereinafter “Niger”) transmitted to the Registrar a certified
copy of a Special Agreement, which was signed on 15 June 2001 in Cotonou
and entered into force on 11 April 2002, whereby the Governments of the two
States agreed to submit to a Chamber of the Court a dispute concerning “the
definitive delimitation of the whole boundary between them”.

2. The Special Agreement of 15 June 2001 provides as follows:
“The Government of the Republic of Benin and the Government of the
Republic of Niger, hereinafter the ‘Parties’;

Whereas, pursuant to the Agreement signed on 8 April 1994, having
provisionally entered into force on the date of its signing, having been rati-
fied by Benin on 17 July 1997 and by Niger on 1 February 2001, and
having definitively entered into force on 15 June 2001, the date on which
the instruments of ratification were exchanged, the two Governments
created the Joint Delimitation Commission for their boundary;
Whereas, notwithstanding six negotiating sessions held by that Commis-
sion, the two States’ experts have been unable to agree on the course of the

joint boundary;
Whereas, under Article 15 of that Agreement of 8 April 1994,
‘the contracting Parties agree to submit all disputes or disagreements
arising out of the application or interpretation of this Agreement to
settlement through diplomatic channels or by the other means of

peaceful settlement provided for by the Charters of the Organization of
African Unity and the United Nations’;
Desiring to achieve as rapidly as possible the settlement of the boundary
dispute between them on the basis of the provisions of the Charter and the
resolutions of the Organization of African Unity and to submit the ques-
tion of the definitive delimitation of the whole boundary between them to
the International Court of Justice, hereinafter the ‘Court’;

Have agreed as follows:
Article 1
Formation of a Chamber of the International Court of Justice

1. The Parties submit the dispute defined in Article 2 below to a cham-
ber of the Court, hereinafter the ‘Chamber’, formed in accordance with the
provisions of the Statute of the Court and the present Special Agreement.
2. Each of the Parties shall exercise the right granted it by Article 31,
paragraph 3, of the Statute of the Court to proceed to choose a judge
ad hoc.

Article 2
Subject of the Dispute
The Court is requested to:

(a) determine the course of the boundary between the Republic of Benin
and the Republic of Niger in the River Niger sector;
(b) specify which State owns each of the islands in the said river, and in
particular Lété Island;
(c) determine the course of the boundary between the two States in the
River Mekrou sector.

996 DIFFÉREND FRONTALIER (ARRÊT )

Article 3
Procédure écrite

1. Sans préjuger d’aucune question relative à la charge de la preuve, les
Parties prient la Chambre d’autoriser la procédure suivante au regard des
pièces de procédure écrite:
a) un mémoire soumis par chacune des Parties au plus tard neuf (9) mois
après l’adoption par la Cour de l’ordonnance constituant la Chambre;
b) un contre-mémoire soumis par chacune des Parties au plus tard neuf

(9) mois après l’échange des mémoires;
c) toutes autres pièces de procédure écrite dont le dépôt, à la demande de
l’une ou l’autre des Parties, aura été autorisé par la Cour ou prescrit
par celle-ci.
2. Les pièces de la procédure écrite, déposées auprès du greffier ne
seront transmises à l’autre Partie que lorsque le greffier aura reçu de ladite
Partie la pièce de procédure correspondante.

Article 4
Procédure orale
Les Parties conviendront, avec l’approbation de la Chambre, de l’ordre
dans lequel elles seront entendues au cours de la procédure orale; à

défaut d’accord entre les Parties, cet ordre sera celui que prescrira la
Chambre.
Article 5
Langue de la procédure

Les Parties conviennent que leurs pièces de procédure écrite et leurs plai-
doiries seront présentées en langue française.
Article 6
Droit applicable

Les règles et principes du droit international qui s’appliquent au diffé-
rend sont ceux énumérés au paragraphe 1 de l’article 38 du Statut de la
Cour internationale de Justice, y compris le principe de la succession
d’Etats aux frontières héritées de la colonisation, à savoir, l’intangibilité
desdites frontières.

Article 7
Arrêt de la Chambre
1. Les Parties acceptent, comme définitif et obligatoire pour elles-
mêmes, l’arrêt de la Chambre, rendu en application du présent compro-
mis.
2. A partir du prononcé de l’arrêt, les Parties disposent de dix-huit

(18) mois pour commencer les travaux de démarcation de la frontière.

3. En cas de difficulté d’exécution de l’arrêt, l’une ou l’autre des Parties
saisira la Cour conformément à l’article 60 du Statut de la Cour.
Article 8
Entrée en vigueur

Le présent accord est soumis à ratification. Il entrera en vigueur à la
date de l’échange des instruments de ratification qui aura lieu dans les
meilleurs délais.

10 FRONTIER DISPUTE (JUDGMENT ) 96

Article 3
Written Proceedings

1. Without prejudice to any question as to the burden of proof, the
Parties request the Chamber to authorize the following procedure for the
written pleadings:
(a) a Memorial filed by each Party not later than nine (9) months after
the adoption by the Court of the Order constituting the Chamber;
(b) a Counter-Memorial filed by each Party not later than nine (9)

months after exchange of the Memorials;
(c) any other pleading whose filing, at the request of either of the Parties,
shall have been authorized or directed by the Court.

2. Pleadings submitted to the Registrar shall not be transmitted to the
other Party until the Registrar has received the corresponding pleading
from that Party.

Article 4
Oral Proceedings
The Parties shall agree, with approval from the Chamber, on the order
in which they are to be heard during the oral proceedings; if the Parties

fail to agree, the order shall be prescribed by the Chamber.

Article 5
Language of the Proceedings

The Parties agree that their written pleadings and their oral argument
shall be presented in the French language.
Article 6
Applicable Law

The rules and principles of international law applicable to the dispute
are those set out in Article 38, paragraph 1, of the Statute of the Interna-
tional Court of Justice, including the principle of State succession to the
boundaries inherited from colonization, that is to say, the intangibility of
those boundaries.

Article 7
Judgment of the Chamber
1. The Parties accept the judgment of the Chamber given pursuant to
the present Special Agreement as final and binding upon them.

2. From the day on which the judgment is rendered, the Parties shall

have eighteen (18) months in which to commence the works of demarca-
tion of the boundary.
3. In case of difficulty in the implementation of the judgment, either
Party may seise the Court pursuant to Article 60 of its Statute.
Article 8
Entry into Force

The present Agreement is subject to ratification. It shall enter into force
on the date on which the instruments of ratification are exchanged, which
shall take place as rapidly as possible.

1097 DIFFÉREND FRONTALIER (ARRÊT )

Article 9
Enregistrement et notification

Le présent accord sera enregistré au Secrétariat des Nations Unies en
application de l’article 102 de la Charte des Nations Unies à l’initiative de
la Partie la plus diligente.
1. En application de l’article 40 du Statut de la Cour, le présent com-
promis sera notifié au greffier de la Cour par une lettre conjointe des
Parties.
2. Si cette notification n’est pas effectuée conformément au paragraphe
précédent dans le délai d’un mois suivant l’entrée en vigueur du présent
compromis, celui-ci sera notifié au greffier de la Cour par la Partie la plus

diligente.
Article 10

Engagement spécial
En attendant l’arrêt de la Chambre, les Parties s’engagent à préserver la
paix, la sécurité et la quiétude au sein des populations des deux Etats.

En foi de quoi le présent compromis établi en deux exemplaires origi-
naux a été signé par les plénipotentiaires.
Fait à Cotonou, le 15 juin 2001.»

3. Conformément au paragraphe 3 de l’article 40 du Statut de la Cour et à
l’article 42 du Règlement, le greffier a transmis copie de la lettre de notification
conjointe, du compromis et du protocole d’échange des instruments de ratifi-
cation au Secrétaire général des Nations Unies, aux Membres des Nations
Unies et aux autres Etats admis à ester devant la Cour.

4. L’article premier du compromis prévoit la saisine d’une chambre devant
être constituée en application du paragraphe 2 de l’article 26 du Statut, ainsi
que la désignation d’un juge ad hoc par chacune des Parties, conformément à
l’article 31 du Statut. Les Parties, dûment consultées par le président de la Cour

au sujet de la composition de la chambre en question, conformément au para-
graphe 2 de l’article 26 du Statut et au paragraphe 2 de l’article 17 du Règle-
ment, ont indiqué qu’elles souhaitaient la formation d’une chambre de cinq
membres, dont les deux juges ad hoc à désigner par elles.
5. Par lettre du 21 août 2002, l’agent adjoint du Bénin a notifié à la Cour la
désignation par son gouvernement de M. Mohamed Bennouna pour siéger en
qualité de juge ad hoc. Par lettre du 11 septembre 2002, l’agent du Niger a noti-
fié à la Cour la désignation par son gouvernement de M. Mohammed Bedjaoui
pour siéger en qualité de juge ad hoc.
6. Par ordonnance du 27 novembre 2002, la Cour, agissant en vertu du para-
graphe 2 de l’article 26 de son Statut et de l’article 17 de son Règlement, a
décidé d’accéder à la demande des Parties tendant à ce qu’une chambre spéciale
soit constituée pour connaître de l’affaire; elle a déclaré que, le 27 novembre

2002, M. Guillaume, président de la Cour, et MM. Ranjeva et Kooijmans,
juges, avaient été élus pour former, avec les juges ad hoc susmentionnés, la
chambre qui serait saisie de l’affaire, et qu’en conséquence ladite chambre, ainsi
composée, était dûment constituée en vertu de cette ordonnance. Conformé-
ment au paragraphe 2 de l’article 18 du Règlement, il est revenu à M. Guillaume,
président de la Cour au moment de la constitution de la Chambre, de présider
la Chambre.

11 FRONTIER DISPUTE (JUDGMENT ) 97

Article 9
Registration and Notification

The present Agreement shall be registered with the Secretariat of the
United Nations pursuant to Article 102 of the United Nations Charter by
the more diligent Party.
1. In accordance with Article 40 of the Statute of the Court, the present
Special Agreement shall be notified to the Registrar of the Court by a joint
letter from the Parties.
2. If such notification is not effected in accordance with the preceding
paragraph within one month from the entry into force of the present
Special Agreement, it shall be notified to the Registrar of the Court by

the more diligent Party.
Article 10

Special Undertaking
Pending the judgment of the Chamber, the Parties undertake to preserve
peace, security and quiet among the peoples of the two States.

In witness whereof, the present Special Agreement, drawn up in two
original copies, has been signed by the plenipotentiaries.
Done at Cotonou, 15 June 2001.”

3. Pursuant to Article 40, paragraph 3, of the Statute of the Court and
Article 42 of the Rules of Court, the Registrar transmitted copies of the
joint letter of notification, of the Special Agreement and of the protocol of
exchange of the instruments of ratification to the Secretary-General of the
United Nations, the Members of the United Nations and other States entitled
to appear before the Court.
4. Article 1 of the Special Agreement provides for the submission of the dis-
pute to a Chamber to be formed in accordance with Article 26, paragraph 2,
of the Statute, with a judge ad hoc to be chosen by each Party pursuant to
Article 31 of the Statute. The Parties, having been duly consulted by the Presi-

dent of the Court regarding the composition of the Chamber, expressed their
wish, pursuant to Article 26, paragraph 2, of the Statute, and to Article 17,
paragraph 2, of the Rules of Court, for the formation of a Chamber of five
members, of whom two would be the judges ad hoc to be chosen by them.
5. By a letter of 21 August 2002 the Deputy Agent of Benin informed the
Court that his Government had chosen Mr. Mohamed Bennouna to sit as
judge ad hoc. By a letter of 11 September 2002 the Agent of Niger informed the
Court that his Government had chosen Mr. Mohammed Bedjaoui to sit as
judge ad hoc.
6. By an Order of 27 November 2002 the Court, acting pursuant to
Article 26, paragraph 2, of the Statute and Article 17 of the Rules of Court,
decided to accede to the request of the Parties that a special Chamber be formed
to deal with the case; it declared that, at an election held on 27 November 2002,

President Guillaume and Judges Ranjeva and Kooijmans had been elected
to form, together with the above-named judges ad hoc, a Chamber to deal with
the case and that accordingly the said Chamber as so composed had been
duly constituted pursuant to that Order. In accordance with Article 18,
paragraph 2, of the Rules of Court, Judge Guillaume, who held the office of
President of the Court when the Chamber was formed, was to preside over
the Chamber.

1198 DIFFÉREND FRONTALIER (ARRÊT )

7. Par la même ordonnance, la Cour, conformément au paragraphe 1 de
l’article 92 de son Règlement, a fixé au 27 août 2003 la date d’expiration du

délai pour le dépôt d’un mémoire de chaque Partie, la suite de la procédure
étant réservée. Les mémoires ont été dûment déposés dans le délai ainsi fixé.
8. Par ordonnance du 11 septembre 2003, le président de la Chambre, eu
égard au paragraphe 1 b) de l’article 3 du compromis, a fixé au 28 mai 2004 la
date d’expiration du délai pour le dépôt d’un contre-mémoire par chaque
Partie, la suite de la procédure étant réservée.
9. La Chambre a tenu une audience le 20 novembre 2003 afin de permettre
aux juges ad hoc de faire la déclaration solennelle requise par le paragraphe 6
de l’article 31 du Statut et l’article 8 du Règlement.
10. Le 28 mai 2004, dans le délai fixé par l’ordonnance du 11 septembre
2003, les Parties ont déposé au Greffe leurs contre-mémoires respectifs. Au
cours d’une réunion que le président de la Chambre a tenue avec les représen-

tants des Parties le 2 juillet 2004 afin de se renseigner auprès de celles-ci sur la
suite de la procédure, les deux Parties ont exprimé le souhait d’être autorisées à
présenter une troisième pièce de procédure écrite. Par ordonnance du
9 juillet 2004, le président de la Chambre, eu égard au paragraphe 1 c) de l’ar-
ticle 3 du compromis, a autorisé le dépôt d’une réplique par chaque Partie
et a fixé au 17 décembre 2004 la date d’expiration du délai pour le dépôt de
ces pièces, la suite de la procédure étant réservée. Les Parties ont déposé
leurs répliques au Greffe dans le délai ainsi fixé.
11. Par lettre du 11 octobre 2004, M. Guillaume, président de la Chambre, a
informé le président de la Cour, conformément au paragraphe 4 de l’article 13
du Statut, qu’il avait pris la décision de démissionner de la Cour à compter du

11 février 2005. Du fait de la vacance que cette démission devait emporter au
sein de la Chambre, le président de la Cour a de nouveau consulté les Parties,
le 11 janvier 2005, au sujet de la composition de la Chambre. Lors d’une élec-
tion tenue le 16 février 2005, M. Abraham a été élu membre de la Chambre
pour occuper le siège devenu vacant à la suite de la démission de M. Guillaume.
Par ordonnance du 16 février 2005, la Cour a déclaré que, en conséquence de
cette élection, la Chambre se trouvait ainsi composée: M. Ranjeva, devenu, en
sa qualité de vice-président de la Cour, président de la Chambre, conformément
au paragraphe 2 de l’article 18 du Règlement; MM. Kooijmans et Abraham,
juges; et MM. Bedjaoui et Bennouna, juges ad hoc.
12. Par lettre du 11 février 2005, l’agent du Niger a exprimé le vŒu de son
gouvernement de produire deux documents nouveaux, conformément aux dis-

positions de l’article 56 du Règlement. Par lettre du 25 février 2005, l’agent du
Bénin a fait savoir à la Chambre que son gouvernement ne s’opposait pas à
cette production. La Chambre ayant décidé d’autoriser la production desdits
documents par le Niger, le greffier a porté cette décision à la connaissance des
Parties par lettres datées du 2 mars 2005.
13. Conformément au paragraphe 2 de l’article 53 du Règlement, la
Chambre, après s’être renseignée auprès des Parties, a décidé que des exem-
plaires des pièces de procédure et des documents annexés seraient rendus
accessibles au public à l’ouverture de la procédure orale.
14. Des audiences ont été tenues les 7, 8, 10 et 11 mars 2005, au cours des-
quelles ont été entendus en leurs plaidoiries et réponses:

Pour le Bénin: S. Exc. M. Rogatien Biaou,
M. elain Pellet,
M Robert Dossou,

12 FRONTIER DISPUTE JUDGMENT ) 98

7. By the same Order, the Court, acting pursuant to Article 92, paragraph 1,
of the Rules of Court, fixed 27 August 2003 as the time-limit for the filing of a
Memorial by each Party and reserved the subsequent procedure for further
decision. The Memorials were duly filed within the time-limit thus fixed.
8. By Order of 11 September 2003, the President of the Chamber, having

regard to Article 3, paragraph 1 (b), of the Special Agreement, fixed 28 May
2004 as the time-limit for the filing of a Counter-Memorial by each Party and
reserved the subsequent procedure for further decision.
9. The Chamber held a public sitting on 20 November 2003 to enable the
judges ad hoc to make the solemn declaration required by Article 31, para-
graph 6, of the Statute and by Article 8 of the Rules of Court.
10. On 28 May 2004, within the time-limit fixed by the Order of 11 Septem-
ber 2003, the Parties filed their respective Counter-Memorials in the Registry.
During a meeting held by the President of the Chamber with the representatives
of the Parties on 2 July 2004, in order to ascertain their views on the subsequent
procedure, the two Parties expressed the wish to be authorized to submit a
third pleading. By Order of 9 July 2004, the President of the Chamber, having
regard to Article 3, paragraph 1 (c), of the Special Agreement, authorized the

filing of a Reply by each Party and fixed 17 December 2004 as the time-limit
therefor, reserving the subsequent procedure for further decision. The Parties
filed their Replies in the Registry within the time-limit thus fixed.

11. By a letter of 11 October 2004, Judge Guillaume, President of the Cham-
ber, informed the President of the Court, pursuant to Article 13, paragraph 4,
of the Statute, that he had decided to resign from the Court with effect from
11 February 2005. Since his resignation would leave a vacancy in the Chamber,
the President of the Court consulted the Parties again on 11 January 2005
regarding the composition of the Chamber. At an election held on 16 February
2005, Judge Abraham was elected a member of the Chamber to fill the seat left
vacant by Judge Guillaume’s resignation. By an Order of 16 February 2005, the
Court declared that, as a result of this election, the Chamber was now com-
posed as follows: Judge Ranjeva, who, in his capacity as Vice-President of the

Court, had become President of the Chamber, pursuant to Article 18, para-
graph 2, of the Rules of Court; Judges Kooijmans and Abraham; and Judges
ad hoc Bedjaoui and Bennouna.
12. By a letter of 11 February 2005, the Agent of Niger expressed his Gov-
ernment’s wish to produce two new documents pursuant to Article 56 of the
Rules of Court. By a letter of 25 February 2005, the Agent of Benin informed
the Chamber that his Government did not object to that production. Following
the decision of the Chamber to authorize the production of those documents
by Niger, the Registrar advised the Parties of that decision by letters dated
2 March 2005.
13. Pursuant to Article 53, paragraph 2, of the Rules of Court, the Chamber,
having ascertained the views of the Parties, decided to make accessible to
the public, with effect from the opening of the oral proceedings, copies of the

written pleadings and of the documents annexed thereto.
14. Public sittings were held on 7, 8, 10 and 11 March 2005, at which the
Chamber heard the oral arguments and replies of:

For Benin: H.E. Mr. Rogatien Biaou,
Mr. Alain Pellet,
Maître Robert Dossou,

1299 DIFFÉREND FRONTALIER ARRÊT )

M. Mathias Forteau,
M. Jean-Marc Thouvenin.
me
Pour le Niger: S. Exc. M Aïchatou Mindaoudou,
M. Jean Salmon,
M. Amadou Tankoano,
M. Gérard Niyungeko,
M. Pierre Klein.

A l’audience, des questions ont été posées par la Chambre, auxquelles il a été
répondu par écrit, conformément au paragraphe 4 de l’article 61 du Règlement.
Chacune des Parties a présenté des observations écrites sur les réponses de
l’autre Partie, conformément à l’article 72 du Règlement.

*

15. Dans la procédure écrite, les conclusions ci-après ont été présentées par
les Parties:

Au nom du Gouvernement du Bénin ,
dans le mémoire:

«Compte tenu de l’ensemble de ces considérations, la République du
Bénin prie la Chambre de la Cour internationale de Justice de décider:

1) que la frontière entre la République du Bénin et la République du
Niger suit le tracé suivant:

— du point de coordonnées 11°54′15″ de latitude nord et 2°25′10″ de
longitude est, elle suit la ligne médiane de la rivière Mékrou jusqu’au
point de confluence avec le fleuve Niger,
— de ce point, la frontière se prolonge jusqu’à la rive gauche du fleuve
qu’elle suit jusqu’au point d’intersection avec la frontière avec le
Nigéria, telle qu’elle est définie par les Accords franco-britanniques
des 29 mai et 19 octobre 1906;

2) que la souveraineté sur chacune des îles du fleuve, et en particulier l’île
de Lété, appartient à la République du Bénin.»
dans le contre-mémoire:

«Pour les motifs exposés tant dans son mémoire que dans le présent
contre-mémoire, la République du Bénin persiste dans ses conclusions et
prie la Chambre de la Cour internationale de Justice de bien vouloir
décider:
1) que la frontière entre la République du Bénin et la République du
Niger suit le tracé suivant:

— du point de coordonnées 11°54′15″ de latitude nord et 2°25′10″ de
longitude est, elle suit la ligne médiane de la rivière Mékrou jusqu’au
point de coordonnées 12°24′29″ de latitude nord et 2°49′38″ de
longitude est,
— de ce point, la frontière suit la rive gauche du fleuve jusqu’au point
de coordonnées 11°41′44″ nord et 3°36′44″ est;

2) que la souveraineté sur chacune des îles du fleuve, et en particulier l’île
de Lété, appartient à la République du Bénin.»

13 FRONTIER DISPUTE (JUDGMENT ) 99

Mr. Mathias Forteau,
Mr. Jean-Marc Thouvenin.

For Niger: H.E. Ms Aïchatou Mindaoudou,
Mr. Jean Salmon,
Mr. Amadou Tankoano,
Mr. Gérard Niyungeko,
Mr. Pierre Klein.
At the hearings questions were put by the Chamber, to which replies were

given in writing pursuant to Article 61, paragraph 4, of the Rules of Court.
Each Party submitted its written comments on the other’s written replies in
accordance with Article 72 of the Rules of Court.

*

15. In the course of the written proceedings, the following submissions were
presented by the Parties:
On behalf of the Government of Benin,

in the Memorial:
“Having regard to all of the foregoing considerations, the Republic of
Benin requests the Chamber of the International Court of Justice to
decide:

(1) that the boundary between the Republic of Benin and the Republic of
Niger takes the following course:
— from the point having co-ordinates 11°54′15″ latitude North and
2°25′10″ longitude East, it follows the median line of the River
Mekrou as far as its point of confluence with the River Niger,
— from that point, the boundary continues as far as the left bank of
the River [Niger], which it follows until it reaches the boundary of
Nigeria, as defined by the Franco-British Agreements of 29 May

and 19 October 1906;
(2) that sovereignty over all of the islands in the River [Niger], and in par-
ticular the island of Lété, lies with the Republic of Benin.”

in the Counter-Memorial:
“For the reasons set out in its Memorial and in the present Counter-
Memorial, the Republic of Benin maintains its submissions and requests
the Chamber of the International Court of Justice to decide:

(1) that the boundary between the Republic of Benin and the Republic of
Niger takes the following course:
— from the point having co-ordinates 11°54′15″ latitude North and
2°25′10″ longitude East, it follows the median line of the River
Mekrou as far as the point having co-ordinates 12°24′29″ latitude
North and 2°49′38″ longitude East,
— from that point, the boundary follows the left bank of the River
[Niger] as far as the point having co-ordinates 11°41′44″ North

and 3°36′44″ East;
(2) that sovereignty over all of the islands in the River [Niger], and in par-
ticular the island of Lété, lies with the Republic of Benin.”

13100 DIFFÉREND FRONTALIER (ARRÊT )

dans la réplique:

«Pour les motifs exposés tant dans son mémoire et son contre-mémoire,
que dans la présente réplique, la République du Bénin persiste dans ses
conclusions et prie la Chambre de la Cour internationale de Justice de bien
vouloir décider:
1) que la frontière entre la République du Bénin et la République du
Niger suit le tracé suivant:

— du point de coordonnées 11°54′15″ de latitude nord et 2°25′10″ de
longitude est, elle suit la ligne médiane de la rivière Mékrou jusqu’au
point de coordonnées 12°24′29″ de latitude nord et 2°49′38″ de
longitude est,
— de ce point, la frontière suit la rive gauche du fleuve jusqu’au point
de coordonnées 11°41′44″ nord et 3°36′44″ est;

2) que la souveraineté sur chacune des îles du fleuve, et en particulier l’île
de Lété, appartient à la République du Bénin.»
Au nom du Gouvernement du Niger ,

dans le mémoire:
«La République du Niger prie la Cour de dire et juger que:

— la frontière entre la République du Bénin et la République du Niger
dans le secteur du fleuve Niger, depuis le confluent de la rivière
Mékrou avec le fleuve Niger jusqu’à la frontière du Nigéria, suit la
ligne des sondages les plus profonds, étant entendu qu’en cas de chan-
gement à l’avenir de cette ligne, la frontière entre la République du
Bénin et la République du Niger suivra ce nouveau tracé;

— la ligne actuelle des sondages les plus profonds dans cette partie du
fleuve détermine l’appartenance des îles à l’une ou à l’autre des Parties;
— les îles situées entre la ligne des sondages les plus profonds et la rive
droite du fleuve, à savoir Tondi Kwaria Barou, Koki Barou, Sandi
Tounga Barou, Gandégabi Barou Kaïna, Dan Koré Guirawa, Barou
Elhadji Dan Djoda, Koundou Barou, Elhadji Chaïbou Barou Kaïna et

Dolé Barou, appartiennent à la République du Bénin;
— les îles situées entre la ligne des sondages les plus profonds et la rive
gauche du fleuve, à savoir Boumba Barou Béri, Boumba Barou Kaïna,
Kouassi Barou, Sansan Goungou, Lété Goungou, Monboye Tounga
Barou, Sini Goungou, Lama Barou, Kotcha Barou, Gagno Goungou,
Kata Goungou, Gandégabi Barou Béri, Guirawa Barou, Elhadji Chaï-
bou Barou Béri, Goussou Barou et Beyo Barou, appartiennent à la
République du Niger;
— l’attribution des îles à la République du Bénin et la République du
Niger doit être considérée comme définitive, même en cas de change-
ment à l’avenir du tracé de la ligne des sondages les plus profonds;
— la frontière entre la République du Bénin et la République du Niger
dans le secteur de la Mékrou suit une ligne composée de deux seg-
ments:

— le premier segment est une ligne droite qui relie le point situé au
confluent de la Mékrou avec le fleuve Niger au point situé à l’inter-
section du méridien de Paris et de la chaîne montagneuse de l’Ata-

14 FRONTIER DISPUTE (JUDGMENT ) 100

in the Reply:

“For the reasons set out in its Memorial and in its Counter-Memorial,
as well as in the present Reply, the Republic of Benin maintains its sub-
missions and requests the Chamber of the International Court of Justice to
decide:
(1) that the boundary between the Republic of Benin and the Republic of
Niger takes the following course:

— from the point having co-ordinates 11°54′15″ latitude North and
2°25′10″ longitude East, it follows the median line of the River
Mekrou as far as the point having co-ordinates 12°24′29″ latitude
North and 2°49′38″ longitude East,
— from that point, the boundary follows the left bank of the River
[Niger] as far as the point having co-ordinates 11°41′44″ North
and 3°36′44″ East;

(2) that sovereignty over all of the islands in the River [Niger], and in par-
ticular the island of Lété, lies with the Republic of Benin.”
On behalf of the Government of Niger,

in the Memorial:
“The Republic of Niger requests the Court to adjudge and declare that:

— the boundary between the Republic of Benin and the Republic of
Niger in the River Niger sector, from the confluence of the River
Mekrou with the River Niger as far as the boundary of Nigeria, fol-
lows the line of deepest soundings, on the understanding that, in the
event of a future change in the course of that line, the boundary
between the Republic of Benin and the Republic of Niger will follow
that new course;
— the current line of deepest soundings in this part of the river deter-
mines which islands belong to each Party;
— the islands located between the line of deepest soundings and the right
bank of the river, namely Tondi Kwaria Barou, Koki Barou, Sandi
Tounga Barou, Gandégabi Barou Kaïna, Dan Koré Guirawa, Barou
Elhadji Dan Djoda, Koundou Barou, Elhadji Chaïbou Barou Kaïna

and Dolé Barou, belong to the Republic of Benin;
— the islands located between the line of deepest soundings and the left
bank of the river, namely Boumba Barou Béri, Boumba Barou Kaïna,
Kouassi Barou, Sansan Goungou, Lété Goungou, Monboye Tounga
Barou, Sini Goungou, Lama Barou, Kotcha Barou, Gagno Goungou,
Kata Goungou, Gandégabi Barou Béri, Guirawa Barou, Elhadji
Chaïbou Barou Béri, Goussou Barou and Beyo Barou, belong to the
Republic of Niger;
— the attribution of islands to the Republic of Benin and the Republic of
Niger shall be regarded as final, even in the event of a future change in
the course of the line of deepest soundings;
— the boundary between the Republic of Benin and the Republic of
Niger in the River Mekrou sector follows a line comprising two parts:

— the first part is a straight line joining the point of confluence of the
River Mekrou with the River Niger to the point where the Paris
meridian meets the Atacora mountain range, indicative co-ordi-

14101 DIFFÉREND FRONTALIER (ARRÊT )

cora, dont les coordonnées indicatives sont les suivantes: latitude:
11°41′50″ nord; longitude: 2°20′14″ est;
— le second segment relie ce dernier point au point d’intersection des
anciennes limites des cercles de Say et de Fada, d’une part, et de
Fada et de l’Atacora, d’autre part, dont les coordonnées indi-

catives sont les suivantes: latitude: 11°44′37″ nord; longitude:
2°18′55″ est.»
dans le contre-mémoire:

«La République du Niger prie la Cour de dire et juger que:
— la frontière entre la République du Bénin et la République du Niger
dans le secteur du fleuve Niger, depuis le confluent de la rivière
Mékrou avec le fleuve Niger jusqu’à la frontière du Nigéria, suit la
ligne des sondages les plus profonds, étant entendu qu’en cas de chan-

gement à l’avenir de cette ligne, la frontière entre la République du
Bénin et la République du Niger suivra ce nouveau tracé;

— la ligne actuelle des sondages les plus profonds dans cette partie du
fleuve détermine l’appartenance des îles à l’une ou à l’autre des parties;
— les îles situées entre la ligne des sondages les plus profonds et la rive
droite du fleuve, à savoir Tondi Kwaria Barou, Koki Barou, Sandi
Tounga Barou, Gandégabi Barou Kaïna, Dan Koré Guirawa, Barou
Elhadji Dan Djoda, Koundou Barou, Elhadji Chaïbou Barou Kaïna et
Dolé Barou appartiennent à la République du Bénin;
— les îles situées entre la ligne des sondages les plus profonds et la rive
gauche du fleuve, à savoir Boumba Barou Béri, Boumba Barou Kaïna,
Kouassi Barou, Sansan Goungou, Lété Goungou, Monboye Tounga

Barou, Sini Goungou, Lama Barou, Kotcha Barou, Gagno Goungou,
Kata Goungou, Gandégabi Barou Béri, Guirawa Barou, Elhadji Chaï-
bou Barou Béri, Goussou Barou et Beyo Barou appartiennent à la
République du Niger;
— l’attribution des îles à la République du Bénin et la République du
Niger doit être considérée comme définitive, même en cas de change-
ment à l’avenir du tracé de la ligne des sondages les plus profonds;
— la frontière entre la République du Bénin et la République du Niger
dans le secteur de la Mékrou suit une ligne composée de deux segments:

— le premier segment est une ligne droite qui relie le point situé au
confluent de la Mékrou avec le fleuve Niger au point situé à l’inter-
section du méridien de Paris et de la chaîne montagneuse de l’Ata-
cora, dont les coordonnées indicatives sont les suivantes: latitude:
11°41′50″ nord; longitude: 2°20′14″ est;
— le second segment relie ce dernier point au point d’intersection des
anciennes limites des cercles de Say et de Fada, d’une part, et de
Fada et de l’Atacora, d’autre part, dont les coordonnées indi-
catives sont les suivantes: latitude: 11°44′37″ nord; longitude:
2°18′55″ est.»

dans la réplique:
«La République du Niger prie la Cour de dire et juger que:

— la frontière entre la République du Bénin et la République du Niger
dans le secteur du fleuve Niger, depuis le confluent de la rivière

15 FRONTIER DISPUTE (JUDGMENT ) 101

nates of which are as follows: latitude: 11°41′50″ North; longi-
tude: 2°20′14″ East;
— the second part of the line joins this latter point to the point where
the former boundary between the cercles of Say and Fada meets
the former boundary between the cercles of Fada and Atacora,

indicative co-ordinates of which are as follows: latitude: 11°44′37″
North; longitude: 2°18′55″ East.”
in the Counter-Memorial:

“The Republic of Niger requests the Court to adjudge and declare that:
— the boundary between the Republic of Benin and the Republic of
Niger in the River Niger sector, from the confluence of the River
Mekrou with the River Niger as far as the boundary of Nigeria, fol-
lows the line of deepest soundings, on the understanding that, in the

event of a future change in the course of that line, the boundary
between the Republic of Benin and the Republic of Niger will follow
that new course;
— the current course of the line of deepest soundings in this part of the
river determines which islands belong to each Party;
— the islands located between the line of deepest soundings and the right
bank of the river, namely Tondi Kwaria Barou, Koki Barou, Sandi
Tounga Barou, Gandégabi Barou Kaïna, Dan Koré Guirawa, Barou
Elhadji Dan Djoda, Koundou Barou, Elhadji Chaïbou Barou Kaïna
and Dolé Barou, belong to the Republic of Benin;
— the islands located between the line of deepest soundings and the left
bank of the river, namely Boumba Barou Béri, Boumba Barou Kaïna,
Kouassi Barou, Sansan Goungou, Lété Goungou, Monboye Tounga

Barou, Sini Goungou, Lama Barou, Kotcha Barou, Gagno Goungou,
Kata Goungou, Gandégabi Barou Béri, Guirawa Barou, Elhadji
Chaïbou Barou Béri, Goussou Barou and Beyo Barou, belong to the
Republic of Niger;
— the attribution of islands to the Republic of Benin and the Republic of
Niger shall be regarded as final, even in the event of a future change in
the course of the line of deepest soundings;
— the boundary between the Republic of Benin and the Republic of
Niger in the River Mekrou sector follows a line comprising two parts:

— the first part is a straight line joining the point of confluence of the
River Mekrou with the River Niger to the point where the Paris
meridian meets the Atacora mountain range, indicative co-ordi-
nates of which are as follows: latitude: 11°41′50″ North; longi-
tude: 2°20′14″ East;
— the second part of the line joins this latter point to the point where
the former boundary between the cercles of Say and Fada meets
the former boundary between the cercles of Fada and Atacora,
indicative co-ordinates of which are as follows: latitude: 11°44′37″
North; longitude: 2°18′55″ East.”

in the Reply:
“The Republic of Niger requests the Court to adjudge and declare that:

— the boundary between the Republic of Benin and the Republic of
Niger in the River Niger sector, from the confluence of the River

15102 DIFFÉREND FRONTALIER (ARRÊT )

Mékrou avec le fleuve Niger jusqu’à la frontière du Nigéria, suit la
ligne des sondages les plus profonds, telle qu’elle peut être établie à la
date de l’indépendance;
— cette ligne détermine l’appartenance des îles à l’une ou à l’autre des
parties;

— les îles entre la ligne des sondages les plus profonds et la rive droite du
fleuve, à savoir Pekinga, Tondi Kwaria Barou, Koki Barou, Sandi
Tounga Barou, Gandégabi Barou Kaïna, Dan Koré Guirawa, Barou
Elhadji Dan Djoda, Koundou Barou et Elhadji Chaïbou Barou Kaïna
appartiennent à la République du Bénin;
— les îles situées entre la ligne des sondages les plus profonds et la rive
gauche du fleuve, à savoir Boumba Barou Béri, Boumba Barou Kaïna,
Kouassi Barou, Sansan Goungou, Lété Goungou, Monboye Tounga
Barou, Sini Goungou, Lama Barou, Kotcha Barou, Gagno Goungou,
Kata Goungou, Gandégabi Barou Béri, Guirawa Barou, Elhadji Chaï-
bou Barou Béri, Goussou Barou, Beyo Barou et Dolé Barou appar-
tiennent à la République du Niger;
— l’attribution des îles à la République du Bénin et la République du

Niger selon la ligne des sondages les plus profonds déterminée à la date
de l’indépendance doit être considérée comme définitive. Il appartien-
dra aux parties de veiller à ce que ce chenal reste le principal chenal
navigable en effectuant les dragages nécessaires;
— la frontière entre la République du Bénin et la République du Niger
dans le secteur de la Mékrou suit une ligne composée de deux segments:
— le premier segment est une ligne droite qui relie le point situé au
confluent de la rivière Mékrou avec le fleuve Niger au point situé à

l’intersection du méridien de Paris et de la chaîne montagneuse de
l’Atacora, dont les coordonnées indicatives sont les suivantes: lati-
tude: 11°41′50″ nord; longitude: 2°20′14″ est;
— le second segment relie ce dernier point au point d’intersection des
anciennes limites des cercles de Say et de Fada, d’une part, et de
Fada et de l’Atacora, d’autre part, dont les coordonnées indi-
catives sont les suivantes: latitude: 11°44′37″ nord; longitude:
2°18′55″ est.»

16. Dans la procédure orale, les conclusions finales ci-après ont été présen-
tées par les Parties:

Au nom du Gouvernement du Bénin ,
«Pour les motifs exposés tant dans ses écritures qu’au cours des plaidoi-
ries orales, la République du Bénin prie la Chambre de la Cour interna-

tionale de Justice de bien vouloir décider:
1) que la frontière entre la République du Bénin et la République du
Niger suit le tracé suivant:

— du point de coordonnées 11°54′15″ de latitude nord et 2°25′10″ de
longitude est, elle suit la ligne médiane de la rivière Mékrou jusqu’au
point de coordonnées 12°24′29″ de latitude nord et 2°49′38″ de
longitude est,
— de ce point, la frontière suit la rive gauche du fleuve jusqu’au point
de coordonnées 11°41′44″ nord et 3°36′44″ est;

16 FRONTIER DISPUTE (JUDGMENT ) 102

Mekrou with the River Niger as far as the boundary of Nigeria, fol-
lows the line of deepest soundings, in so far as that line can be estab-
lished as it was at the date of independence;
— that line determines which islands belong to each Party;

— the islands between the line of deepest soundings and the right bank of
the river, namely Pekinga, Tondi Kwaria Barou, Koki Barou, Sandi
Tounga Barou, Gandégabi Barou Kaïna, Dan Koré Guirawa, Barou
Elhadji Dan Djoda, Koundou Barou and Elhadji Chaïbou Barou
Kaïna, belong to the Republic of Benin;
— the islands located between the line of deepest soundings and the left
bank of the river, namely Boumba Barou Béri, Boumba Barou Kaïna,
Kouassi Barou, Sansan Goungou, Lété Goungou, Monboye Tounga
Barou, Sini Goungou, Lama Barou, Kotcha Barou, Gagno Goungou,
Kata Goungou, Gandégabi Barou Béri, Guirawa Barou, Elhadji
Chaïbou Barou Béri, Goussou Barou, Beyo Barou and Dolé Barou,
belong to the Republic of Niger;
— the attribution of islands to the Republic of Benin and the Republic of

Niger according to the line of deepest soundings as determined at the
date of independence shall be regarded as final. It shall be for the
Parties to ensure that this channel remains the principal navigable
channel by carrying out dredging works as necessary;
— the boundary between the Republic of Benin and the Republic of
Niger in the River Mekrou sector follows a line comprising two parts:
— the first part is a straight line joining the point of confluence of the
River Mekrou with the River Niger to the point where the Paris

meridian meets the Atacora mountain range, indicative co-ordi-
nates of which are as follows: latitude: 11°41′50″ North; longi-
tude: 2°20′14″ East;
— the second part of the line joins this latter point to the point where
the former boundary between the cercles of Say and Fada meets
the former boundary between the cercles of Fada and Atacora,
indicative co-ordinates of which are as follows: latitude: 11°44′37″
North; longitude: 2°18′55″ East.”

16. At the oral proceedings, the following submissions were presented by the
Parties:

On behalf of the Government of Benin,
“For the reasons set out in its written and oral pleadings, the Republic
of Benin requests the Chamber of the International Court of Justice to

decide:
(1) that the boundary between the Republic of Benin and the Republic of
Niger takes the following course:

— from the point having co-ordinates 11°54′15″ latitude North and
2°25′10″ longitude East, it follows the median line of the River
Mekrou as far as the point having co-ordinates 12°24′29″ latitude
North and 2°49′38″ longitude East,
— from that point, the boundary follows the left bank of the River
[Niger] as far as the point having co-ordinates 11°41′44″ North
and 3°36′44″ East;

16103 DIFFÉREND FRONTALIER (ARRÊT )

2) que la souveraineté sur chacune des îles du fleuve, et en particulier l’île
de Lété, appartient à la République du Bénin.»

Au nom du Gouvernement du Niger ,
«La République du Niger prie la Cour de dire et juger que:

1) La frontière entre la République du Bénin et la République du Niger
suit la ligne des sondages les plus profonds dans le fleuve Niger, telle
qu’elle a pu être établie à la date de l’indépendance, et ce, depuis le
point de coordonnées 12°24′27″ de latitude nord et 2°49′36″ de lon-
gitude est, jusqu’au point de coordonnées 11°41′40,7″ de latitude nord
et 3°36′44″ de longitude est.
2) Cette ligne détermine l’appartenance des îles à l’une ou à l’autre des
Parties.

— Les îles situées entre la ligne des sondages les plus profonds et la
rive droite du fleuve, à savoir Pekinga, Tondi Kwaria Barou, Koki
Barou, Sandi Tounga Barou, Gandégabi Barou Kaïna, Dan Koré
Guirawa, Barou Elhadji Dan Djoda, Koundou Barou et Elhadji
Chaïbou Barou Kaïna appartiennent à la République du Bénin.
— Les îles situées entre la ligne des sondages les plus profonds et la
rive gauche du fleuve, à savoir Boumba Barou Béri, Boumba Barou
Kaïna, Kouassi Barou, Sansan Goungou, Lété Goungou, Mon-
boye Tounga Barou, Sini Goungou, Lama Barou, Kotcha Barou,
Gagno Goungou, Kata Goungou, Gandégabi Barou Béri, Guirawa
Barou, Elhadji Chaïbou Barou Béri, Goussou Barou, Beyo Barou
et Dolé Barou appartiennent à la République du Niger.

3) L’attribution des îles à la République du Bénin et la République du
Niger selon la ligne des sondages les plus profonds déterminée à la date
de l’indépendance doit être considérée comme définitive.
4) En ce qui concerne la limite frontalière sur les ponts de Gaya-Malan-
ville, celle-ci passe par le milieu de chacun de ces ouvrages.
5) La frontière entre la République du Bénin et la République du Niger
dans le secteur de la Mékrou suit une ligne composée de deux seg-
ments:

— le premier segment est une ligne droite qui relie le point situé au
confluent de la rivière Mékrou avec le fleuve Niger au point situé à
l’intersection du méridien de Paris et de la chaîne montagneuse de
l’Atacora, dont les coordonnées indicatives sont les suivantes: lati-
tude: 11°41′50″ nord; longitude: 2°20′14″ est;
— le second segment relie ce dernier point au point d’intersection des
anciennes limites des cercles de Say et de Fada, d’une part, et de
Fada et de l’Atacora, d’autre part, dont les coordonnées indicatives
sont les suivantes: latitude: 11°44′37″ nord; longitude: 2°18′55″
est.»

*
* *
17. La mission confiée à la Chambre en la présente espèce par le com-
promis du 15 juin 2001 consiste à déterminer le tracé de l’ensemble de la

frontière entre le Bénin et le Niger et à dire auquel des deux Etats appar-
tient chacune des îles du fleuve Niger dans ce secteur, notamment l’île de
Lété.

17 FRONTIER DISPUTE JUDGMENT ) 103

(2) that sovereignty over all of the islands in the River [Niger], and in par-
ticular the island of Lété, lies with the Republic of Benin.”

On behalf of the Government of Niger,
“The Republic of Niger requests the Court to adjudge and declare that:

(1) The boundary between the Republic of Benin and the Republic of
Niger follows the line of deepest soundings in the River Niger, in so
far as that line could be established at the date of independence, from
the point having co-ordinates latitude 12°24′27″ North, longitude
2°49′36″ East, as far as the point having co-ordinates latitude
11°41′40.7″ North, longitude 3°36′44″ East.
(2) That line determines which islands belong to each Party.

— The islands between the line of deepest soundings and the right
bank of the river, namely Pekinga, Tondi Kwaria Barou, Koki
Barou, Sandi Tounga Barou, Gandégabi Barou Kaïna, Dan Koré
Guirawa, Barou Elhadji Dan Djoda, Koundou Barou and Elhadji
Chaïbou Barou Kaïna, belong to the Republic of Benin.
— The islands located between the line of deepest soundings and the
left bank of the river, namely Boumba Barou Béri, Boumba Barou
Kaïna, Kouassi Barou, Sansan Goungou, Lété Goungou, Mon-
boye Tounga Barou, Sini Goungou, Lama Barou, Kotcha Barou,
Gagno Goungou, Kata Goungou, Gandégabi Barou Béri, Guirawa
Barou, Elhadji Chaïbou Barou Béri, Goussou Barou, Beyo Barou
and Dolé Barou, belong to the Republic of Niger.

(3) The attribution of islands to the Republic of Benin and the Republic
of Niger according to the line of deepest soundings as determined at
the date of independence shall be regarded as final.
(4) With regard to the Gaya-Malanville bridges, the boundary passes
through the middle of each of those structures.
(5) The boundary between the Republic of Benin and the Republic of
Niger in the River Mekrou sector follows a line comprising two parts:

— the first part is a straight line joining the point of confluence of the
River Mekrou with the River Niger to the point where the Paris
meridian meets the Atacora mountain range, indicative co-ordi-
nates of which are as follows: latitude: 11°41′50″ North; longi-
tude: 2°20′14″ East;
— the second part of the line joins this latter point to the point where
the former boundary between the cercles of Say and Fada meets
the former boundary between the cercles of Fada and Atacora,
indicative co-ordinates of which are as follows: latitude: 11°44′37″
North; longitude: 2°18′55″ East.”

*
* *
17. The task assigned to the Chamber in the present case by the
Special Agreement of 15 June 2001 is to determine the course of the

whole boundary between Benin and Niger and to specify to which State
each of the islands in the River Niger sector belongs, and in particular
the island of Lété.

17104 DIFFÉREND FRONTALIER (ARRÊT )

Le Bénin et le Niger sont situés en Afrique occidentale. La République
du Bénin, anciennement connue sous le nom de République du Dahomey

(de 1960 à 1975), puis de République populaire du Bénin (de 1975 à
1990), couvre une superficie de 112 622 kilomètres carrés; elle se trouve
limitée au sud par l’océan Atlantique, à l’ouest par le Togo, au nord-
ouest par le Burkina Faso, au nord par le Niger et à l’est par le Nigéria.
La République du Niger, dont la superficie est de 1 267 000 kilomètres

carrés, est limitée au sud par le Nigéria, au sud-ouest par le Bénin, à
l’ouest par le Burkina Faso, au nord-ouest par le Mali, au nord par la
Libye et l’Algérie, et à l’est par le Tchad. Le croquis n° 1, à la page 105
ci-après, illustre la situation générale des territoires des Parties.
18. L’article 2 du compromis divise la frontière contestée en deux sec-

teurs: celui de la rivière Mékrou, à l’ouest, et celui du fleuve Niger, à l’est.
Le croquis n° 2, à la page 106 ci-après, présente une vue générale de cette
frontière.
Dans sa partie occidentale, cette frontière suit un tracé orienté approxi-
mativement de sud-ouest en nord-est, traversant une forêt dont la végéta-
tion est de transition soudano-sahélienne, depuis un point marquant la

limite entre les deux Etats et le Burkina Faso jusqu’au confluent de la
rivière Mékrou avec le fleuve Niger.
Dans sa partie orientale, la frontière suit ce fleuve, en direction du sud-
est, sur une longueur d’environ 150 kilomètres à partir dudit confluent et
aboutit à un point marquant la limite des deux Etats avec le Nigéria. Les

Parties ont présenté des descriptions divergentes des caractéristiques du
fleuve Niger dans la région. Selon le Bénin, le fleuve subit un phénomène
d’ensablement qui entraînerait un déplacement dans le temps de son
cours et affecterait particulièrement sa rive droite, beaucoup moins stable
que la rive gauche. Bien que reconnaissant l’existence dudit phénomène,

le Niger soutient qu’il n’y a pas eu, en raison de la nature des roches du
bief fluvial concerné, de changement significatif dans le tracé du chenal
principal du fleuve sur une période de plus de cent ans, et qu’il n’y a pas
de différence importante dans la configuration de l’une et l’autre des
rives. Dans ce secteur, trois affluents (la Mékrou, l’Alibori et la Sota)

débouchent sur la rive droite du fleuve Niger, qui connaît de ce fait deux
crues annuelles, l’une en janvier-mars et l’autre en septembre-octobre.
Les Parties ont des vues opposées sur la question de savoir si dans la zone
à délimiter le fleuve est navigable en période de basses eaux: tandis que le
Bénin allègue qu’il ne l’est pas, le Niger soutient que la navigation y est
possible pendant toute l’année pour certains types d’embarcations.

19. Plusieurs îles sont situées sur le bief fluvial concerné, dont le
nombre exact et l’appartenance à l’une ou l’autre des Parties font
l’objet de contestations en la présente instance.
L’île de Lété, à laquelle se réfère explicitement l’alinéa b) de l’article 2
du compromis, est la plus grande de ces îles, couvrant une quarantaine de

kilomètres carrés. Elle s’étend sur une longueur de 16300 mètres depuis
un point situé en face des villages de Kwara Tegui (Bénin) et d’Ouna
(Niger) jusqu’à un point se trouvant face aux villages de Karimama

18 FRONTIER DISPUTE (JUDGMENT ) 104

Benin and Niger are States in western Africa. The Republic of Benin,
formerly known as the Republic of Dahomey (from 1960 to 1975) then as

the People’s Republic of Benin (from 1975 to 1990), covers an area of
112,622 sq km; it is bounded to the south by the Atlantic Ocean, to the
west by Togo, to the north-west by Burkina Faso, to the north by Niger
and to the east by Nigeria. The Republic of Niger, with an area of
1,267,000 sq km, is bounded to the south by Nigeria, to the south-west by

Benin, to the west by Burkina Faso, to the north-west by Mali, to the
north by Libya and Algeria, and to the east by Chad. Sketch-map No. 1,
on page 105 below, illustrates the general situation of the territories of
the Parties.
18. Article 2 of the Special Agreement divides the disputed boundary

into two sectors: the River Mekrou sector in the west and the River
Niger sector in the east. Sketch-map No. 2, on page 106 below, gives a
general view of this boundary.
The western part of this boundary follows a course running approxi-
mately south-west to north-east, passing through woodland composed of
transitional Sudano-Sahelian vegetation, from a point marking the

boundary between the two States and Burkina Faso as far as the conflu-
ence of the River Mekrou and the River Niger.
The eastern part of the boundary follows the River Niger in a south-
easterly direction over a distance of some 150 km from that confluence
and ends at a point marking the boundary of the two States with Nigeria.

The Parties have submitted differing descriptions of the characteristics of
the River Niger in the region. According to Benin, the river is subject to
siltation, which has led to a change in its course over time particularly
affecting the right bank, which is much less stable than the left bank.
Although it acknowledges the existence of this phenomenon, Niger main-

tains that, because of the nature of the rocks in the stretch of river con-
cerned, there has been no significant change in the course of the main
channel for more than a century, and that there is no substantial differ-
ence in the configuration of each bank. In this sector, three tributaries
(the Mekrou, the Alibori and the Sota) enter the River Niger from the

right bank, as a result of which it floods twice a year, in January-March
and in September-October. The Parties have conflicting views as to
whether, in the area subject to delimitation, the river is navigable during
the low-water season: Benin claims that it is not but Niger maintains that
navigation is possible throughout the year for certain types of craft.

19. There are several islands within the stretch concerned; their exact
number and their attribution to either Party are matters of dispute in the
present case.
The island of Lété, referred to expressly in Article 2 (b) of the Special
Agreement, is the largest, covering approximately 40 sq km. It extends

16,300 m from a point opposite the villages of Kwara Tegui (Benin) and
Ouna (Niger) to a point opposite the villages of Karimama (Benin) and
Albarkaizé (Niger). The approximate co-ordinates of the extremities of

18105 DIFFÉREND FRONTALIER (ARRÊT )

19FRONTIER DISPUTE (JUDGMENT ) 105

19106 DIFFÉREND FRONTALIER (ARRÊT )FRONTIER DISPUTE (JUDGMENT ) 106107 DIFFÉREND FRONTALIER (ARRÊT )

(Bénin) et d’Albarkaizé (Niger). Les coordonnées approximatives des

extrémités de l’île sont: en amont, 12°9’55′ de latitude nord et 3°6′47″ de
longitude est; et, en aval, 12°3′43″ de latitude nord et 3°13′39″ de lon-
gitude est. Fertile et dotée de riches pâturages, l’île est habitée en perma-
nence; selon les informations fournies par le Niger, sa population était de
quelque deux mille habitants en 2000.

**

20. Le différend frontalier qui oppose les Parties s’inscrit dans un
contexte historique marqué par l’accession à l’indépendance des terri-

toires qui relevaient de l’Afrique occidentale françaier (dénommée ci-
après l’«AOF»). Le Bénin, indépendant depuis le 1 août 1960, corres-
pond à l’ancienne colonie du Dahomey, et le Niger, indépendant depuis
le 3 août 1960, à un territoire ayant connu différents avatars adminis-

tratifs au cours de la période coloniale.

21. Les deux Parties ont fait état, dans leurs pièces de procédure,
d’incidents survenus sur l’île de Lété à la veille de leur accession à l’indé-
pendance, en 1959 et 1960. A la suite de ces événements, les deux Etats

mirent en place un processus de règlement amiable du différend frontalier
les opposant: en 1961 et 1963, deux commissions mixtes daho-nigériennes
se réunirent pour discuter de la question.
En octobre 1963, la crise s’aggrava entre le Dahomey et le Niger, en
particulier au sujet de l’île de Lété. Chacun des deux Etats publia par la

suite un livre blanc où étaient notamment exposées leurs positions res-
pectives au sujet du différend frontalier.
De nouvelles tentatives de règlement pacifique eurent lieu dans les années
suivantes, qui aboutirent à une conférence tenue à Yamoussoukro le 18 jan-
vier 1965, au cours de laquelle les Parties convinrent, «jusqu’au règlement

définitif du litige sur l’île, de permettre aux nationaux des deux pays de
vivre en parfaite harmonie sur cette île». La question de la souveraineté sur
l’île de Lété ne fut cependant pas résolue et de nouveaux incidents se pro-
duisirent dans les années suivantes, notamment en 1993 et 1998.
22. Le 8 avril 1994, le Bénin et le Niger conclurent un accord portant

création de la commission mixte paritaire de délimitation de leur fron-
tière commune, dont le mandat comprenait le recensement, la collecte et
l’analyse des documents relatifs à la frontière, ainsi que la définition pré-
cise de celle-ci. Cette commission tint six sessions entre septembre 1995
et juin 2000.

Les efforts pour parvenir à une solution négociée du différend ayant
échoué, la commission proposa aux autorités des deux Etats de saisir par
compromis la Cour internationale de Justice. Le compromis fut signé à
Cotonou le 15 juin 2001 et entra en vigueur le 11 avril 2002.

**

21 FRONTIER DISPUTE (JUDGMENT ) 107

the island are: upstream, 12°9′55″ latitude North and 3°6′47″ longitude
East; downstream, 12°3′43″ latitude North and 3°13′39″ longitude East.

The island is fertile, with rich pastures, and is permanently inhabited;
according to information supplied by Niger, its population numbered
some 2,000 in the year 2000.

**

20. The frontier dispute between the Parties is set within a historical
context marked by the accession to independence of the territories that
were formerly part of French West Africa (“Afrique occidentale

française”, hereinafter “AOF”). Benin, which has been independent since
1 August 1960, corresponds to the former colony of Dahomey, and
Niger, which has been independent since 3 August 1960, corresponds to a
territory which underwent various administrative transformations during
the colonial period.
21. In their written pleadings, both Parties referred to incidents that

occurred on the island of Lété on the eve of their independence, in 1959
and 1960. Following those events, the two States set up a process for the
friendly settlement of their frontier dispute: in 1961 and 1963 two Daho-
mey-Niger joint commissions met to discuss the matter.

In October 1963 the crisis between Dahomey and Niger deepened, in
particular regarding the island of Lété. Each State subsequently pub-
lished a White Paper setting out, inter alia, their respective positions
regarding the frontier dispute.
There were fresh attempts to reach a peaceful settlement in the years

that followed, culminating in a conference held in Yamoussoukro on
18 January 1965, in the course of which the Parties agreed “until the dis-
pute over the island is finally settled, to allow nationals of both countries
to live in perfect harmony on that island”. However, the issue of sover-
eignty over the island of Lété was not resolved and there were further

incidents in subsequent years, notably in 1993 and 1998.
22. On 8 April 1994 Benin and Niger entered into an agreement
creating a joint commission for the delimitation of their common
border, whose terms of reference included the enumeration, collection
and analysis of documents relating to the frontier and the precise
establishment thereof. The commission held six meetings between Sep-

tember 1995 and June 2000.
Since efforts to arrive at a negotiated solution to the dispute were
unsuccessful, the commission proposed that the Governments of the
two States bring the dispute before the International Court of Justice
by Special Agreement. The Special Agreement was signed in Cotonou on

15 June 2001 and entered into force on 11 April 2002.

**

21108 DIFFÉREND FRONTALIER (ARRÊT )

23. Aux termes de l’article 6 du compromis («Droit applicable»), les

règles et principes du droit international qui s’appliquent au présent dif-
férend comprennent «le principe de la succession d’Etats aux frontières
héritées de la colonisation, à savoir, l’intangibilité desdites frontières». Il
ressort des termes de cette disposition ainsi que de l’argumentation des
Parties que celles-ci conviennent de la pertinence du principe de l’uti pos-

sidetis juris pour la détermination de leur frontière commune. Comme la
Chambre constituée en l’affaire du Différend frontalier (Burkina Faso/
République du Mali) a eu l’occasion de l’indiquer, l’existence de ce prin-
cipe a été reconnue à plusieurs reprises dans le contexte africain (Diffé-
rend frontalier (Burkina Faso/République du Mali), arrêt, C.I.J. Recueil

1986, p. 565, par. 20); elle l’a été, récemment encore, à l’alinéa b) de
l’article 4 de l’acte constitutif, signé à Lomé le 11 juillet 2000, de l’Union
africaine, dont le Bénin et le Niger sont des membres. Ladite Chambre a
précisé que le principe considéré «accorde au titre juridique la préémi-

nence sur la possession effective comme base de la souveraineté» et «vise,
avant tout, à assurer le respect des limites territoriales au moment de
l’accession à l’indépendance», y compris des anciennes délimitations
administratives établies pendant l’époque coloniale et devenues frontières
internationales (C.I.J. Recueil 1986, p. 586-587, par. 63, et p. 566, par. 23).

24. En application du principe de l’uti possidetis juris, la présente
Chambre doit donc rechercher quelle est, dans l’affaire dont elle est sai-
sie, la frontière héritée de l’administration française. Les Parties s’accor-
dent pour dire que les dates à prendre en considération à cet effet sont

celles auxquerles elles ont respectivement accédé à l’indépendance, à
savoir les 1 et 3 août 1960; la Chambre observe qu’aucune modification
de la frontière n’est intervenue entre ces deux moments très proches dans
le temps.
25. Néanmoins, les Parties ont parfois formulé des opinions diffé-

rentes s’agissant de certains aspects de l’application du principe de l’uti
possidetis juris en l’espèce.
En premier lieu, le Niger soutient que ce principe n’exclut pas que la
Chambre puisse tenir compte, le cas échéant, des réalités physiques pos-
térieures à l’accession à l’indépendance, afin de s’assurer que l’arrêt rendu

aura une portée effective et concrète entre les Parties: ainsi, tout en priant
la Chambre de préciser à quel Etat appartient chacune des îles du fleuve
Niger par référence à la ligne des sondages les plus profonds à la date de
l’indépendance, le Niger lui demande de considérer à cet effet unique-
ment les îles existant à l’heure actuelle.

Le Bénin souligne quant à lui qu’en application stricte du principe de
l’uti possidetis juris il serait inacceptable de se référer à la situation
actuelle pour déterminer l’appartenance des îles au moment où les Parties
ont accédé à l’indépendance.
La Chambre constate qu’en tout état de cause les Parties s’accordent

sur le fait que le tracé de leur frontière commune doit être établi, confor-
mément au principe de l’uti possidetis juris, par référence à la situation

22 FRONTIER DISPUTE JUDGMENT ) 108

23. Under Article 6 of the Special Agreement (“Applicable Law”), the
rules and principles of international law applicable to the present dispute

include “the principle of State succession to the boundaries inherited
from colonization, that is to say, the intangibility of those boundaries”. It
follows from the wording of this provision and from the arguments of the
Parties that they are in agreement on the relevance of the principle of uti
possidetis juris for the purposes of determining their common border. As

the Chamber formed in the case concerning the Frontier Dispute (Burkina
Faso/Republic of Mali) had occasion to state, the existence of this prin-
ciple has been recognized on several occasions in the African context
(Frontier Dispute (Burkina Faso/Republic of Mali), Judgment, I.C.J.
Reports 1986, p. 565, para. 20); it was recognized again recently, in

Article 4 (b) of the Constitutive Act of the African Union, of which
Benin and Niger are members, signed in Lomé on 11 July 2000. That
Chamber stated that, according to the principle in question, “pre-
eminence [is] accorded to legal title over effective possession as a basis
of sovereignty” and that its essence lies “in its primary aim of securing
respect for the territorial boundaries at the moment when independence

is achieved”, including former administrative delimitations established
during the colonial period that became international frontiers (I.C.J.
Reports 1986, pp. 586-587, para. 63, and p. 566, para. 23).
24. On the basis of the principle of uti possidetis juris, the present
Chamber must thus seek to determine, in the case before it, the boundary

that was inherited from the French administration. The Parties agree that
the dates to be taken into account for this purpose are those of their
respective independence, namely 1 and 3 August 1960; the Chamber
would observe that there was no change in the frontier between these two
very close dates.

25. The Parties have nonetheless sometimes expressed differing
opinions regarding certain aspects of the application of the uti possidetis
juris principle in the present case.
Firstly, Niger maintains that this principle does not preclude the Cham-

ber from taking account, where appropriate, of the physical realities sub-
sequent to independence, in order to ensure that the Judgment will have
meaningful and practical significance between the Parties. Consequently,
in requesting the Chamber to indicate to which State each of the islands
in the River Niger belongs, by reference to the line of deepest soundings
at the date of independence, Niger asks it to consider for this purpose

only those islands that exist at the present time.
Benin, for its part, argues that, if the uti possidetis juris principle is to
be applied strictly, it would be unacceptable to refer to the present situa-
tion in order to determine to which Party the islands belonged at the date
of independence.

The Chamber observes that, in any event, the Parties agree that the
course of their common boundary should be determined, in accordance
with the uti possidetis juris principle, by reference to the physical situa-

22109 DIFFÉREND FRONTALIER (ARRÊT )

physique à laquelle le droit colonial français s’est appliqué, telle qu’elle
existait à la date des indépendances. Les conséquences de ce tracé sur le

terrain, notamment en ce qui concerne l’appartenance des îles du fleuve à
l’une ou l’autre des Parties, doivent cependant s’apprécier par rapport
aux réalités physiques contemporaines et la Chambre ne saurait ignorer,
dans l’accomplissement de la tâche qui lui est confiée par les Parties aux
termes de l’article 2 du compromis, l’apparition ou la disparition éven-

tuelle de certaines îles sur le bief fluvial concerné.
26. En deuxième lieu, le Bénin et le Niger ont avancé des vues diver-
gentes à propos des documents ou des cartes sur lesquels la Chambre doit
fonder sa détermination de leur frontière commune.
Le Niger invoque, à l’appui de la délimitation qu’il revendique, cer-

tains documents et cartes postérieurs à la date des indépendances, et ce
non seulement pour démontrer des réalités physiques actuelles, mais éga-
lement aux fins de déterminer la situation existant à l’époque coloniale.
Selon le Niger, il doit être procédé à une telle détermination sur la base
des études les plus proches dans le temps de l’accession des Parties à
l’indépendance, sans se limiter aux études antérieures à la date des indé-

pendances.
Le Bénin estime au contraire que la Chambre devrait fonder sa déci-
sion sur des études et documents antérieurs à la date critique.
La Chambre ne saurait exclure à priori que des cartes, études ou autres
documents postérieurs à cette date puissent être pertinents pour établir,

en application du principe de l’uti possidetis juris, la situation qui existait
alors. En tout état de cause, le principe de l’uti possidetis ayant pour effet
de geler le titre territorial (Différend frontalier (Burkina Faso/République
du Mali), arrêt, C.I.J. Recueil 1986 , p. 568, par. 29), la prise en consi-
dération de documents postérieurs à la date des indépendances ne saurait

conduire à une quelconque modification de l’«instantané territorial» à la
date critique sauf, bien entendu, dans l’hypothèse où semblables docu-
ments exprimeraient clairement l’accord des Parties à une telle fin.
27. Les Parties ont, en troisième lieu, débattu de la valeur juridique, au
regard du principe de l’uti possidetis juris, des effectivités postcoloniales.

La Chambre note que les deux Parties ont parfois cherché à confirmer
le titre juridique dont elles se réclament en faisant valoir des actes par
lesquels leurs autorités auraient, après 1960, exercé la souveraineté sur les
territoires contestés; de telles effectivités ont, entre autres, été invoquées
par le Niger à propos d’activités intéressant le fleuve et ses îles, et par le
Bénin à propos d’activités intéressant la rive droite de la rivière Mékrou.

Une telle démarche ne doit pas nécessairement être exclue. En effet,
comme l’a indiqué la Chambre chargée de connaître de l’affaire du Dif-
férend frontalier terrestre, insulaire et maritime (El Salvador/Honduras;
Nicaragua (intervenant)) , il peut être tenu

«compte, dans certains cas, d’éléments de preuve documentaire qui
découlent d’effectivités postérieures à l’indépendance quand ... ces

23 FRONTIER DISPUTE (JUDGMENT ) 109

tion to which French colonial law was applied, as that situation existed at
the dates of independence. However, the consequences of such a course

on the ground, particularly with regard to the question of to which Party
the islands in the River Niger belong, must be assessed in relation to
present-day physical realities and, in carrying out the task assigned to it
under Article 2 of the Special Agreement, the Chamber cannot disregard
the possible appearance or disappearance of certain islands in the stretch

concerned.
26. Secondly, Benin and Niger have put forward differing views with
respect to the documents or maps on which the Chamber should base its
determination of their common boundary.
In support of its delimitation claims, Niger relies on certain documents

and maps that are posterior to the dates of independence, not only to
demonstrate current physical realities but also to establish the situation
existing in the colonial era. According to Niger, that situation must be
determined on the basis of the studies conducted closest in time to the
Parties’ accession to independence, without being confined to those con-
ducted prior to the dates of independence.

Benin considers, to the contrary, that the Chamber should base its
decision on research and documents prior to the critical date.
The Chamber cannot exclude a priori the possibility that maps, research
or other documents subsequent to that date may be relevant in order to

establish, in application of the uti possidetis juris principle, the situation
that existed at the time. In any event, since the effect of the uti possidetis
principle is to freeze the territorial title (Frontier Dispute (Burkina Faso/
Republic of Mali), Judgment, I.C.J. Reports 1986 , p. 568, para. 29), the
examination of documents posterior to independence cannot lead to any

modification of the “photograph of the territory” at the critical date
unless, of course, such documents clearly express the Parties’ agreement
to such a change.
27. Thirdly, the Parties have discussed the legal value, in the light of
the uti possidetis juris principle, of post-colonial effectivités.

The Chamber notes that both Parties have on occasion sought to con-
firm the legal title which they claim by relying on acts whereby their
authorities allegedly exercised sovereignty over the disputed territories
after 1960; such effectivités have been invoked by Niger inter alia in
respect of activities relating to the River Niger and its islands, and by
Benin in respect of activities relating to the right bank of the River

Mekrou.
Such an approach should not necessarily be excluded. As stated by the
Chamber formed in the case concerning the Land, Island and Maritime
Frontier Dispute (El Salvador/Honduras: Nicaragua intervening) ,tisi
possible to

“have regard . . . in certain instances, to documentary evidence of
post-independence effectivités w en..hyardiosni

23110 DIFFÉREND FRONTALIER (ARRÊT )

éléments apportent des précisions sur la frontière de l’uti possidetis ...,
à condition qu’il existe une relation entre les effectivités en cause et

la détermination de cette frontière» (arrêt, C.I.J. Recueil 1992 ,
p. 399, par. 62).

*

28. Les Parties s’accordent à reconnaître que la détermination du tracé
de la frontière et l’attribution des îles du fleuve Niger à l’une ou l’autre
d’entre elles doit, en application du principe de l’uti possidetis juris,
s’apprécier à la lumière du droit colonial français, dit «droit d’outre-
mer». Elles se disent également d’accord sur l’identification des règles

pertinentes de ce droit, mais en offrent des interprétations divergentes.
Avant de se pencher sur ces règles, la Chambre rappellera que, lorsque
référence est faite à un droit interne en pareil contexte, ce droit intervient,

«non en tant que tel (comme s’il y avait un continuum juris, un relais
juridique entre ce droit et le droit international), mais seulement
comme un élément de fait, parmi d’autres, ou comme moyen de
preuve et de démonstration ... [du] «legs colonial»» (Différend fron-
talier (Burkina Faso/République du Mali), arrêt, C.I.J. Recueil

1986, p. 568, par. 30).
29. Ainsi que l’a déjà exposé la Chambre constituée en l’affaire du Dif-

férend frontalier (Burkina Faso/République du Mali) (C.I.J. Recueil 1986,
p. 568-569, par. 31), les possessions françaises en Afrique occidentale
furent dotées, par décret du président de la République française en date
du 16 juin 1895, d’une organisation administrative territoriale centralisée,
placée sous l’autorité d’un gouverneur général. L’AOF ainsi créée était

divisée en colonies, à la tête desquelles se trouvaient des lieutenants-gou-
verneurs, elles-mêmes constituées de circonscriptions de base dénommées
cercles et administrées par des commandants de cercle; chaque cercle
était à son tour composé de subdivisions, administrées par des chefs de
subdivision, comprenant des cantons, qui regroupaient plusieurs villages.

30. Les Parties reconnaissent que la création et la suppression des
colonies étaient du ressort des autorités métropolitaines: le président de
la République française, agissant par décret, sous l’empire de la constitu-
tion de la Troisième République, puis le Parlement français, après l’adop-
tion de la constitution du 27 octobre 1946.
La compétence pour créer des subdivisions territoriales au sein d’une

même colonie relevait en revanche de l’autorité de l’AOF jusqu’en 1957,
lorsqu’elle fut transférée aux institutions représentatives locales.
L’article 5 du décret du président de la République française, du
18 octobre 1904, portant réorganisation de l’AOF, attribua au gouver-
neur général compétence pour «détermin[er] en conseil de gouvernement

et sur la proposition des lieutenants-gouverneurs intéressés les circons-
criptions administratives dans chacune des colonies».
Dans sa circulaire n° 114c du 3 novembre 1912, relative à la forme à

24 FRONTIER DISPUTE JUDGMENT ) 110

respect of the . . . uti possidetis juris boundary, providing a relation-
ship exists between the effectivités concerned and the determination

of that boundary” (Judgment, I.C.J. Reports 1992, p. 399, para. 62).

*

28. The Parties both acknowledge that, in accordance with the prin-
ciple of uti possidetis juris, the course of the frontier and the attribution
of islands in the River Niger to either one of them must be determined in
the light of French colonial law, known as “droit d’outre-mer”. They
also agree on the identification of the relevant rules of that law, but do

not share the same interpretation thereof.
Before turning to those rules, the Chamber would recall that, when ref-
erence is made to domestic law in such a context, that law is applicable

“not in itself (as if there were a sort of continuum juris, a legal relay
between such law and international law), but only as one factual ele-
ment among others, or as evidence indicative of . . . the ‘colonial
heritage’ ” (Frontier Dispute (Burkina Faso/Republic of Mali), Judg-
ment, I.C.J. Reports 1986 , p. 568, para. 30).

29. As the Chamber in the case concerning the Frontier Dispute

(Burkina Faso/Republic of Mali) (I.C.J. Reports 1986, pp. 568-569,
para. 31) already observed, the territorial administration of the French
possessions in West Africa was centralized by a decree of the President of
the French Republic of 16 June 1895 and placed under the authority of a
Governor-General. The entity of the AOF thus created was divided into

colonies, headed by Lieutenant-Governors and themselves made up of
basic units called “cercles” which were administered by commandants de
cercle; each cercle was in turn composed of subdivisions, each adminis-
tered by a chef de subdivision. The subdivisions consisted of cantons,
which grouped together a number of villages.

30. The Parties acknowledge that the creation and abolition of colo-
nies fell within the jurisdiction of the authorities of metropolitan France:
the President of the French Republic, acting by decree, under the Con-
stitution of the Third Republic, and subsequently the French Parliament,
following the adoption of the Constitution of 27 October 1946.
The power to create territorial subdivisions within a single colony, on

the other hand, was vested in the AOF until being transferred to the local
representative institutions in 1957.
Article 5 of the decree of the President of the French Republic, dated
18 October 1904, providing for the reorganization of the AOF, vested the
Governor-General with authority to “determine in government council

(conseil de gouvernement) , and on the proposal of the Lieutenant-Gov-
ernors concerned, the administrative districts in each of the colonies”.
In his circular No. 114c of 3 November 1912, concerning the form of

24111 DIFFÉREND FRONTALIER (ARRÊT )

donner aux actes portant organisation des circonscriptions et subdivi-
sions administratives, le gouverneur général interpréta ce texte comme lui

réservant «le droit de fixer ... le nombre et l’étendue des cercles qui cons-
titu[aient], dans l’intérieur des Colonies, l’unité administrative réelle»,
mais précisa qu’il était «admis que les Lieutenants-Gouverneurs conser-
veraient la faculté de déterminer, par des actes émanant de leur propre
autorité, les subdivisions territoriales créées dans l’intérieur de ces

cercles». D’après cette circulaire, «toute mesure intéressant la circons-
cription administrative, l’unité territoriale proprement dite, c’est-à-dire
affectant le cercle, soit dans son existence (créations ou suppressions),
soit dans son étendue, soit dans sa dénomination, soit dans l’emplacement
de son chef-lieu», devait être sanctionnée par un arrêté général pris en

conseil de gouvernement; il appartenait aux lieutenants-gouverneurs «de
préciser, par des arrêtés, dont [le gouverneur général se] réserv[ait] l’appro-
bation, les limites topographiques exactes et détaillées de chacune de ces
circonscriptions», ainsi que, «dans l’intérieur des cercles, [de] fixer ... le
nombre et l’étendue des subdivisions territoriales ... et l’emplacement de
leur centre» par des actes locaux.

31. Le Bénin allègue qu’au vu de ces textes il convient de distinguer les
règles applicables à la création des colonies et de leurs subdivisions de
celles relatives à la fixation des limites territoriales. A l’audience, le Bénin
n’en a pas moins reconnu que le principe selon lequel les mêmes autorités
habilitées à créer des colonies ou des circonscriptions administratives

avaient le pouvoir d’en définir ou d’en modifier les limites s’appliquait
certainement aux colonies. Il a toutefois maintenu que ce pouvoir n’était
pas exclusif et que ledit principe ne s’appliquait sans doute pas s’agissant
des limites internes aux colonies. En tout état de cause, les autorités
locales, au premier chef les lieutenants-gouverneurs, auraient eu compé-

tence, en vertu des règles relatives à la fixation des limites territoriales,
pour préciser les décisions des autorités centrales.
Le Niger soutient en revanche que le pouvoir de créer une colonie,
reconnu par les textes susmentionnés, emportait le pouvoir implicite d’en
fixer l’étendue globale, de laquelle pouvaient être déduites des limites plus

ou moins précises selon le cas. Il s’ensuivait, selon le Niger, que les règles
en matière de création et d’organisation des circonscriptions administra-
tives coloniales attribuaient des compétences implicites aux autorités
métropolitaines, en matière de détermination des limites interterritoriales,
et aux autorités de l’AOF, pour la délimitation des circonscriptions et
subdivisions administratives. Les lieutenants-gouverneurs n’auraient eu

compétence en cette matière que dans certaines circonstances précises et
suivant une procédure et des formalités prescrites par lesdits textes.

**

32. Aux fins de mieux comprendre le contexte historique dans lequel se
placent les revendications des Parties en ce qui concerne la détermination

25 FRONTIER DISPUTE (JUDGMENT ) 111

instruments for the organization of administrative districts and subdivi-
sions, the Governor-General interpreted this text as conferring upon him

“the right to establish . . . the number and extent of the cercles which,
within the colonies, constitute[d] the actual administrative unit”, but
pointed out that it was “acknowledged that the Lieutenant-Governors
would retain the power to determine the territorial subdivisions created
within these cercles by measures adopted under their own authority”.

According to that circular, “any measure concerning the administrative
district, the territorial unit proper, i.e. affecting the cercle, in terms of its
existence (creation or abolition), its extent, its name, or the location of its
administrative centre”, was to be confirmed by an arrêté général adopted
in government council; it lay with the Lieutenant-Governors “to define,

by means of arrêtés, the approval of which [was] reserved to [the Gover-
nor-General], the exact and detailed topographical boundaries of each of
these districts”, as well as “within the cercles, [to] fix . . . the number and
extent of the territorial subdivisions . . . and the location of their centre”
by means of local decisions.

31. Benin submits that, in the light of these texts, the rules applicable
to the creation of colonies and their subdivisions should be distinguished
from those relating to the establishment of territorial boundaries. At the
hearings, Benin nevertheless acknowledged that the principle whereby
authorities empowered to create colonies or administrative districts were

also competent to define or modify the boundaries thereof was certainly
applicable to colonies. However, Benin contended that such competence
was not exclusive and that in all likelihood the said principle did not
apply in respect of the internal boundaries within colonies. In any event,
the local authorities, headed by the Lieutenant-Governors, had author-

ity, by virtue of the rules governing the fixing of territorial boundaries, to
clarify central authorities’ decisions.
Niger, on the other hand, contends that the power to create colonies,
as conferred by the above-mentioned texts, entailed the implicit power to
establish their overall extent, from which boundaries of varying precision

could be determined on a case-by-case basis. According to Niger, it fol-
lowed from this that the rules concerning the creation and organization
of colonial administrative districts gave implicit prerogatives to the French
metropolitan authorities for the determination of inter-territorial bounda-
ries, and to the authorities of the AOF for the delimitation of adminis-
trative districts and their subdivisions. The Lieutenant-Governors’ com-

petence in this matter was confined to certain specific circumstances,
according to a procedure and formalities laid down by the above-
mentioned texts.

**

32. For a better understanding of the historical context in which the
Parties’ claims stand in relation to the determination of the frontier and

25112 DIFFÉREND FRONTALIER (ARRÊT )

de la frontière et l’appartenance des îles du fleuve Niger, il convient de
retracer brièvement l’évolution du statut juridique des territoires concer-
nés pendant la période coloniale.
33. Dans la seconde moitié du XIX siècle, la France s’était d’abord

implantée le long du littoral du Dahomey, à Cotonou et à Porto Novo.
Au terme d’un conflit armé avec le souverain local dans les années 1880 et
1890, elle consolida sa présence dans la région en plaçant d’abord le
Dahomey sous protectorat (1892), puis en créant la «colonie du Daho-
mey et dépendances» (décret du 22 juin 1894). La France lança ensuite

des expéditions depuis ses possessions du Dahomey vers le nord, ainsi
que depuis le Soudan vers le sud et l’est, qui lui permirent, à l’automne
1897, d’occuper la vallée du fleuve Niger (notamment le secteur entre Say
et Boussa).
L’occupation française fut consacrée, pour la région du nord-ouest du

Dahomey, par une convention conclue avec l’Allemagne le 23 juillet 1897
et, pour celle du nord-est du Dahomey, par une convention conclue avec
la Grande-Bretagne le 14 juin 1898. Par une convention du 8 avril 1904,
certains ajustements furent apportés à la ligne établie en 1898 aux fins de

séparer les zones d’influence française et britannique; les parties à cette
convention fixèrent les limites de leurs possessions respectives suivant ces
ajustements par une convention du 29 mai 1906, pour ce qui est de la
région à l’est du fleuve Niger, et par un accord du 19 octobre 1906, pour
les territoires se trouvant entre le golfe de Guinée et ce fleuve; des opé-

rations d’abornement, consignées dans un procès-verbal en date du
19 février 1910, furent par la suite réalisées par la commission franco-
anglaise de délimitation des territoires situés entre le Niger et le lac
Tchad.
34. AlafinduXIX e siècle, lorsque la colonie du Dahomey fut incor-

porée à l’AOF par décret du 17 octobre 1899, elle englobait, dans la
région concernée par le présent différend, des territoires situés sur les
deux rives du fleuve Niger. En vertu du même décret, qui avait décidé la
dislocation du Soudan français et la répartition des territoires qui appar-

tenaient à celui-ci entre différentes colonies et deux territoires militaires
spécialement créés, le territoire de Say fut également attribué au Daho-
mey; ce rattachement fut rendu effectif par arrêté du gouverneur du
Dahomey en date du 20 mars 1901.
Par arrêté du 23 juillet 1900, le gouverneur général de l’AOF décida

la création d’un troisième territoire militaire s’étendant sur les régions
de la rive gauche du fleuve Niger de Say au lac Tchad. Cet arrêté de
1900 fut suivi d’un décret du président de la République française du
20 décembre 1900 ayant le même objet. La limite entre le troisième

territoire militaire et le premier territoire militaire créé en 1899 fut par la
suite fixée par arrêté du gouverneur général de l’AOF du 20 mars 1902.

Par décret du 18 octobre 1904 portant réorganisation du gouvernement
général de l’AOF, le président de la République française créa notam-

ment la colonie du Haut-Sénégal et Niger comprenant «les anciens terri-

26 FRONTIER DISPUTE (JUDGMENT ) 112

to the question of to whom the islands in the River Niger belong, the
evolution of the legal status of the territories concerned during the colo-

nial period should be briefly recapitulated.
33. In the second half of the nineteenth century, France initially estab-
lished settlements along the coast of Dahomey, at Cotonou and Porto
Novo. Following an armed conflict with the local chieftain in the 1880s
and 1890s, it consolidated its presence in the region first by placing

Dahomey under protectorate (1892), and then by creating the “colony of
Dahomey and dependencies” (decree of 22 June 1894). France subse-
quently launched expeditions northwards from its possessions in Daho-
mey, as well as southwards and eastwards from Sudan, which enabled it,
in the autumn of 1897, to occupy the valley of the River Niger (in par-

ticular the sector between Say and Boussa).
The French occupation was expressly formalized, as regards the region
of north-western Dahomey, by a convention concluded with Germany on
23 July 1897, and as regards north-eastern Dahomey, by a convention
concluded with Great Britain on 14 June 1898. By means of a convention
of 8 April 1904, certain adjustments were made to the line established in

1898 in order to separate the French and British areas of influence. The
parties to that convention fixed the boundaries of their respective posses-
sions in accordance with those adjustments by means of a convention of
29 May 1906 in respect of the region to the east of the River Niger, and
by means of an agreement of 19 October 1906 in respect of the territories

between the Gulf of Guinea and that river; demarcation operations,
documented in an official record dated 19 February 1910, were subse-
quently carried out by the Anglo-French Commission for the delimita-
tion of the territories situated between the Niger and Lake Chad.
34. At the end of the nineteenth century, when the colony of Dahomey

was incorporated into the AOF by decree of 17 October 1899, it encom-
passed, in the region concerned by the present dispute, territories situated
on both banks of the River Niger. By virtue of the same decree, which
had provided for the dissolution of French Sudan and the apportionment
of the territories it had comprised among different colonies and two spe-

cially created military territories, the territory of Say was also attributed
to Dahomey. This territorial incorporation was put into effect by an
arrêté of the Governor of Dahomey dated 20 March 1901.
By arrêté of 23 July 1900, the Governor-General of the AOF decided
to establish a third military territory encompassing the regions on the left
bank of the River Niger from Say to Lake Chad. That 1900 arrêté was

followed by a decree of the President of the French Republic dated
20 December 1900 with the same object. The boundary between the
Third Military Territory and the First Military Territory created in 1899
was subsequently determined by an arrêté of the Governor-General of
the AOF, dated 20 March 1902.

By a decree of 18 October 1904 on the reorganization of the General
Government of the AOF, the President of the French Republic inter alia
established the colony of Haut-Sénégal et Niger comprising “the former

26113 DIFFÉREND FRONTALIER (ARRÊT )

toires du Haut-Sénégal et du Moyen-Niger et ceux qui form[aient] le
troisième territoire militaire». La colonie nouvellement créée était com-
posée de «cercles d’administration civile», ainsi que du «territoire mili-
taire du Niger», formé par les anciens premier et troisième territoires

militaires.
Par décret du 2 mars 1907, les cercles de Fada-N’Gourma et de Say
furent détachés du Dahomey pour être rattachés à la colonie du Haut-
Sénégal et Niger. La limite intercoloniale fixée par ce décret fut revue à
deux reprises dans sa partie occidentale, d’abord par un décret du

12 août 1909, puis par un décret du 23 avril 1913.
35. Le 7 septembre 1911, un autre décret détacha le territoire militaire
du Niger de la colonie du Haut-Sénégal et Niger (le cercle de Say demeu-
rant une circonscription de cette dernière), pour en faire une subdivision
administrative dépendant directement du gouvernement général de
er
l’AOF. Ce territoire militaire devint, le 1 janvier 1921, le territoire
civil du Niger, puis fut transformé en colonie autonome par décret du
13 octobre 1922.
Entre-temps, le décret du 1 ermars 1919 avait décidé la création de la

colonie de la Haute-Volta, qui s’était vu attribuer notamment les cercles
de Say et de Fada-N’Gourma faisant jusqu’alors partie du Haut-Sénégal
et Niger.
Par décret du 28 décembre 1926, certains cantons du cercle de Dori et
le cercle de Say (à l’exception du canton Gourmanché-de-Botou) furent

détachés de la Haute-Volta pour être rattachés au Niger. Un arrêté
général du 31 août 1927 et son erratum du 5 octobre de la même année
fixèrent la limite entre les colonies de la Haute-Volta et du Niger.

La colonie de la Haute-Volta fut supprimée par décret du 5 sep-

tembre 1932, puis reconstituée avec la même assise territoriale par la
loi n° 47-1707 du 4 septembre 1947; pendant la période intermédiaire,
les cercles de Fada et de Dori (à l’exception du canton d’Aribinda)
furent rattachés au Niger.

36. Au cours de la période coloniale, l’organisation administrative du
Dahomey et du Niger fit l’objet de plusieurs dispositions successives.
Après sa création en 1894, la colonie du Dahomey et dépendances fut
organisée par arrêté du gouverneur par intérim en date du 11 août 1898:
cet arrêté instituait quatre cercles dans la colonie, dont celui du Moyen-

Niger, qui comprenait notamment «les territoires du Zaberma ou Dendi
situés sur les deux rives du Niger et leurs dépendances», et celui du
Gourma, qui était constitué par «les provinces de Fada N’Gourma, de
Pama, de Matiacouali, de Kodjar, de Botou et leurs dépendances». Les

divisions territoriales de la colonie furent réorganisées par des arrêtés du
gouverneur général de l’AOF des 8 décembre 1934 et 27 octobre 1938:
ces deux arrêtés identifiaient notamment les limites des cercles de Kandi
et de Natitingou, contigus à la colonie du Niger.
Le Niger fit l’objet de réorganisations internes successives par arrêtés

du gouverneur général de l’AOF du 26 décembre 1904, du 31 décembre

27 FRONTIER DISPUTE JUDGMENT ) 113

territories of Haut-Sénégal and Moyen-Niger and those which form[ed]
the Third Military Territory”. The newly created colony was composed

of “cercles under civil administration” as well as the “Military Territory
of Niger”, constituted by the former First and Third Military Territories.

By decree of 2 March 1907, the cercles of Fada-N’Gourma and Say
were detached from Dahomey and incorporated into the colony of Haut-

Sénégal et Niger. The intercolonial boundary fixed by that decree was
revised on two occasions in its western part, first by a decree of 12 August
1909, and subsequently by a decree of 23 April 1913.
35. On 7 September 1911, a further decree separated the Military Ter-
ritory of Niger from the colony of Haut-Sénégal et Niger (the cercle of

Say remaining as a district of that colony), in order to make it an admin-
istrative subdivision under the direct control of the office of the Govern-
ment-General of the AOF. On 1 January 1921, that military territory
became the Civil Territory of Niger, and was then made an autonomous
colony by decree of 13 October 1922.
In the meantime, the decree of 1 March 1919 had provided for the

establishment of the colony of Haute-Volta, to which were attributed,
inter alia, the cercles of Say and Fada-N’Gourma, which had hitherto
formed part of Haut-Sénégal et Niger.
By decree of 28 December 1926, certain cantons in the cercle of Dori
and the cercle of Say (with the exception of the canton of Gourmanché-

de-Botou) were detached from Haute-Volta and incorporated into Niger.
An arrêté général of 31 August 1927 and the erratum thereto of 5 Octo-
ber of the same year determined the boundary between the colonies of
Haute-Volta and Niger.
The colony of Haute-Volta was abolished by decree of 5 September

1932, then reconstituted with the same territorial basis by Law No. 47-
1707 of 4 September 1947; in the intervening period, the cercles of Fada
and Dori (excluding the canton of Aribinda) were incorporated into
Niger.
36. During the colonial period, the administrative organization of

Dahomey and Niger was the subject of several successive enactments.
Following its establishment in 1894, the colony of Dahomey and
dependencies was organized by arrêté of the Governor ad interim, dated
11 August 1898; that arrêté established four cercles in the colony, includ-
ing that of Moyen-Niger, which comprised inter alia “the territories of
Zaberma or Dendi situated on either side of the Niger and their depen-

dencies” and that of Gourma, which comprised “the provinces of Fada
N’Gourma, Pama, Matiacouali, Kodjar, Botou and their dependencies”.
The territorial divisions of the colony were reorganized by arrêtés of the
Governor-General of the AOF, dated 8 December 1934 and 27 October
1938; those two arrêtés inter alia defined the boundaries of the cercles of

Kandi and of Natitingou, adjoining the colony of Niger.
The internal reorganization of Niger was the subject of successive
arrêtés of the Governor-General of the AOF, dated 26 December 1904,

27114 DIFFÉREND FRONTALIER (ARRÊT )

1907, du 14 décembre 1908, du 22 juin 1910, du 23 novembre 1912 et du
22 janvier 1927; à la veille de l’indépendance, à la suite d’un arrêté géné-

ral du 30 mars 1956 ajoutant sept nouveaux cercles dans la colonie, le
Niger comptait seize cercles.

**

37. La Chambre décrira à présent les principaux documents pertinents
aux fins du règlement du différend frontalier. Il convient de distinguer, à
cet égard, les documents concernant la détermination du tracé de la fron-

tière dans le secteur du fleuve Niger et l’appartenance des îles de ce fleuve
à l’une ou l’autre des Parties, d’une part, et ceux relatifs à la délimitation
dans le secteur de la rivière Mékrou, d’autre part.
38. S’agissant du secteur du fleuve Niger et des îles, les documents
essentiels sont, par ordre chronologique, les suivants:

— l’arrêté général du 23 juillet 1900 créant un troisième territoire mili-
taire dont le chef-lieu était établi à Zinder. L’article premier de cet

arrêté disposait que ce territoire «s’étend[ait] sur les régions de la rive
gauche du Niger de Say au lac Tchad qui [avaient] été placées dans la
sphère d’influence française par la convention du 14 juin 1898»;

— le décret du 20 décembre 1900 constituant un troisième territoire mili-

taire entre le Niger et le Tchad;
— la lettre n° 163 du ministre des colonies en date du 7 septembre 1901
adressée au gouverneur général de l’AOF. Dans cette lettre, le mi-
nistre se référait à une communication antérieure par laquelle le gou-
verneur général lui avait transmis deux rapports du gouverneur du

Dahomey «envisagea[nt] la question de la délimitation entre le Daho-
mey et le troisième territoire militaire, et indiqua[nt] le cours du Niger
comme la meilleure ligne de démarcation, au double point de vue
géographique et politique». En réponse à l’avis du gouverneur géné-
ral selon lequel cette proposition semblait «très acceptable», le mi-

nistre indiquait dans sa lettre qu’il «partage[ait] sur ce point [la]
manière de voir» de celui-ci;
— la lettre n° 54 du 3 juillet 1914, par laquelle l’administrateur adjoint
Sadoux, commandant du secteur de Gaya (Niger), communiquait au
commandant du cercle du Moyen-Niger (Dahomey) «[un] tableau
des îles du [fleuve] Niger avec l’indication du grand bras du fleuve et

de la colonie à laquelle par suite ces îles appart[enaient]», établi par
ses soins «dans le but unique de déterminer nettement le cas dans
lequel des laissez-passer de pacage d[evai]ent être délivrés aux Peuhls
des deux rives et de délimiter la compétence territoriale des tribunaux
indigènes des deux colonies». Dans sa lettre, l’administrateur adjoint

indiquait qu’il «cro[yait] ... que c’[était] le chenal principal qui [devait]
servir de délimitation» entre les territoires concernés, «le comman-
dant du secteur de Guéné [lui] ayant cité [l’année précédente] à ce

28 FRONTIER DISPUTE (JUDGMENT ) 114

31 December 1907, 14 December 1908, 22 June 1910, 23 November 1912
and 22 January 1927. On the eve of independence, as a result of an arrêté

général of 30 March 1956 adding seven new cercles to the colony, Niger
comprised 16 cercles.

**

37. The Chamber will now describe the main documents relevant to
the settlement of the frontier dispute. In this connection, a distinction
should be made between those documents that concern the determination

of the course of the boundary in the River Niger sector and the question
of to whom the islands in that river belong and those documents that
relate to the delimitation in the River Mekrou sector.
38. As regards the sector of the River Niger and the islands therein,
the essential documents, in chronological order, are as follows:

— the arrêté général of 23 July 1900 creating a Third Military Territory,
the administrative centre of which was established at Zinder. Article 1

of this arrêté stated that this territory “encompass[ed] the areas on
the left bank of the Niger between Say and Lake Chad that [had
been] placed within the French sphere of influence by the Convention
of 14 June 1898”;
— the decree of 20 December 1900 creating a Third Military Territory

between the Niger and Lake Chad;
— letter No. 163 from the Minister for the Colonies, dated 7 September
1901, addressed to the Governor-General of the AOF. In this letter,
the Minister referred to a previous communication, by which the
Governor-General had transmitted two reports to him from the Gov-

ernor of Dahomey “regarding the question of the delimitation between
Dahomey and the Third Military Territory, and indicating the course
of the Niger as the best demarcation line, both from a geographical
and political perspective”. In response to the Governor-General’s
view that this proposal seemed “highly acceptable”, the Minister indi-

cated in his letter that “on this point, he share[d] [the] view” of the
Governor-General;
— letter No. 54 of 3 July 1914, under cover of which administrateur
adjoint Sadoux, commandant of the secteur of Gaya (Niger), sent to
the commandant of the cercle of Moyen-Niger (Dahomey) “a table of
the islands in the River Niger indicating the major branch of the river

and the colony to which the islands therefore belong[ed]”, which he
had prepared “for the sole purpose of clearly determining when graz-
ing permits [should] be issued to the Peuhls from both banks and
delimiting the territorial jurisdiction of the indigenous tribunals in the
two colonies”. In his letter, the administrateur adjoint indicated that

he “believe[d] . . . that it [was] the main channel that [should] serve as
delimitation” between the territories concerned, “the commandant of
the secteur of Guéné having cited to [him the previous year] a text on

28115 DIFFÉREND FRONTALIER (ARRÊT )

sujet un texte qui se trouv[ait] à Kandi mais [qu’il] ne poss[édait] pas
à Gaya»;
— l’arrêté général n 2812/AP du 8 décembre 1934 et l’arrêté général
n 3578/AP du 27 octobre 1938, portant tous deux réorganisation des

divisions territoriales de la colonie du Dahomey. Ce dernier arrêté,
dont le texte est quasi identique à celui de 1934 dans sa partie perti-
nente pour la présente affaire, indiquait à son article premier que le
cercle de Kandi était limité

«[à] l’est, par la frontière de la Nigéria [l’arrêté de 1934 se référait
à «la frontière nigérienne»] jusqu’au Niger;
[a]u nord-est, par le cours du Niger jusqu’à son confluent avec la
Mékrou ...».

L’article 2 précisait que les limites des cercles étaient celles qui étaient
tracées sur une carte du Dahomey à l’échelle de 1/500000 jointe à
l’arrêté (l’article 2 de l’arrêté de 1934 ayant un contenu identique);

aucune des Parties n’a cependant pu retrouver, aux fins de la présente
affaire, les cartes sur lesquelles avaient été reportées ces limites;
— la lettre n° 3722/APA du 27 août 1954, par laquelle le secrétaire géné-
ral Raynier, gouverneur par intérim du Niger, faisait savoir au chef
de la subdivision de Gaya (Niger), sous couvert du commandant du

cercle de Dosso (Niger), «que la limite du territoire du Niger [était]
constituée de la ligne des plus hautes eaux, côté rive gauche du fleuve,
à partir du village de Bandofay, jusqu’à la frontière du Nigéria» et
que «[e]n conséquence toutes les îles situées dans cette partie du

fleuve [faisaient] partie du territoire du Dahomey». Les Parties ont
appelé l’attention de la Chambre sur d’autres correspondances rela-
tives à la limite intercoloniale, échangées entre les autorités du Niger,
entre celles du Dahomey et entre les deux colonies au cours de l’année
1954, ainsi que dans les années suivantes (notamment en 1956), qui

permettraient d’apprécier la valeur juridique et la portée de la lettre
susmentionnée.

39. S’agissant du secteur de la rivière Mékrou, les documents essentiels
de l’époque coloniale sont, par ordre chronologique, les suivants:

— un décret du 2 mars 1907, rattachant à la colonie du Haut-Sénégal et
Niger les cercles de Fada N’Gourma et de Say. L’article premier de ce
décret établissait ce qui suit:

«[l]a limite entre la colonie du Haut-Sénégal et Niger et celle du
Dahomey est constituée, à partir de la frontière du Togo, par les
limites actuelles du cercle du Gourma jusqu’à la rencontre de la
chaîne montagneuse de l’Atakora dont elle suit le sommet jusqu’au
point d’intersection avec le méridien de Paris, d’où elle suit une

ligne droite dans la direction nord-est et aboutissant au confluent
de la rivière Mékrou avec le Niger»;
— un décret du 12 août 1909, dont l’article premier disposait que «[l]a

limite entre le cercle du Gourma (Haut-Sénégal et Niger) et le cercle

29 FRONTIER DISPUTE (JUDGMENT ) 115

this subject, which [was] in Kandi, but [which he] [did] not have in
Gaya”;

— arrêté général No. 2812/AP of 8 December 1934 and arrêté général
No. 3578/AP of 27 October 1938, both reorganizing the territorial
divisions of the colony of Dahomey. The latter, whose text is virtually
identical to that of 1934 in the part relevant to the present case, indi-
cated in Article 1 that the cercle of Kandi was bounded

“[in] the east, by the frontier of Nigeria [the 1934 arrêté referred to
‘the frontier of Niger’] as far as the Niger;
[i]n the north-east, by the course of the Niger to its confluence with

the Mekrou . . .”.
Article 2 stated that the boundaries of the cercles were those drawn
on a 1:500,000 map of Dahomey appended to the arrêté (Article 2 of

the 1934 arrêté being identical in content). However, neither of the
Parties has been able, for the purposes of the present case, to locate
the maps on which those boundaries had been drawn;
— letter No. 3722/APA of 27 August 1954, by which Secretary-General
Raynier, Governor ad interim of Niger, informed the chef of the sub-

division of Gaya (Niger), through the commandant of the cercle of
Dosso (Niger), “that the boundary of the Territory of Niger [was]
constituted by the line of highest water, on the left bank of the river,
from the village of Bandofay to the frontier of Nigeria” and that
“[c]onsequently, all the islands situated in this part of the river
[formed] part of the Territory of Dahomey”. The Parties have drawn

the attention of the Chamber to other letters relating to the inter-
colonial boundary exchanged between the authorities of Niger,
between the authorities of Dahomey and between the two colonies
during 1954, as well as in subsequent years (in 1956 for example),
which would allegedly make it possible to assess the legal value and

the significance of the aforementioned letter.
39. With respect to the River Mekrou sector, the essential documents

from the colonial period are, in chronological order, as follows:
— a decree of 2 March 1907, incorporating the cercles of Fada
N’Gourma and Say into the colony of Haut-Sénégal et Niger.

Article 1 of this decree provided as follows:
“[t]he boundary between the colony of Haut-Sénégal et Niger and
the colony of Dahomey is formed, from the boundary of Togo, by

the present boundary of the cercle of Gourma until it reaches the
Atakora mountain range, whose summit it follows until it meets
the Paris meridian, from which point it runs in a straight line in a
north-easterly direction, terminating at the confluence of the River
Mekrou with the Niger”;

— a decree of 12 August 1909, Article 1 of which provided that “[t]he
boundary between the cercle of Gourma (Haut-Sénégal et Niger) and

29116 DIFFÉREND FRONTALIER (ARRÊT )

de Djougou (Dahomey)» était constituée notamment par

«[l]a chaîne de l’Altacora, dont elle suit le sommet, ou, plus exac-
tement, une ligne parallèle à la piste Konkobiri, Tandangou,

Sangou qui longe le pied de la montagne, distante de celle-ci
de 8 kilomètres»;

— un décret du 23 avril 1913, dont l’article premier établissait que «[l]a
limite entre le cercle de Fada-N’Gourma (Haut-Sénégal et Niger) et
de l’Atacora (Dahomey)» était déterminée notamment par

«une ligne parallèle, à l’est, à la piste de Compongou, Konkobiri,
Batchango, qui longe le pied de la chaîne de l’Atacora, distante de
celle-ci de 8 kilomètres et prolongée, jusqu’à sa rencontre, avec le

cours supérieur de la rivière Pendjari»;
— un décret du 1 ermars 1919 portant division de la colonie du Haut-

Sénégal et Niger et création de la colonie de la Haute-Volta;
— un arrêté général du 16 avril 1926 fixant certaines conditions d’exécu-
tion du décret du 10 mars 1925 portant réglementation de la chasse et
institution de parcs de refuge en AOF;
— un arrêté général pris par le gouverneur général par intérim de l’AOF

le 31 août 1927, fixant les limites des colonies de la Haute-Volta et
du Niger. Bien que concernant, ainsi que son texte le précise, la fron-
tière entre la Haute-Volta et le Niger, cet arrêté prévoyait, au para-
graphe 2 de l’article premier, que les limites entre le cercle de Say et
la Haute-Volta étaient constituées

«[a]u Sud-Ouest, [par] une ligne partant approximativement de la
Sirba à hauteur du parallèle de Say pour aboutir à la Mékrou;

[a]u Sud-Est, par la Mékrou de ce point jusqu’à son confluent avec
le Niger».

Cet arrêté général fut modifié, entre autres sur ce point, par un «erra-
tum» du 5 octobre 1927, publié au Journal officiel de l’AOF du
15 octobre 1927, dont le dernier alinéa de l’article premier établissait
uniquement que la limite des colonies du Niger et de la Haute-Volta

«remont[ait] ... le cours de la Tapoa jusqu’au point où elle rencon-
tr[ait] l’ancienne limite des cercles de Fada et de Say, qu’elle sui[vait]
jusqu’à son intersection avec le cours de la Mékrou»;
— les arrêtés généraux des 8 décembre 1934 et 27 octobre 1938 susmen-
tionnés, qui indiquaient notamment que la limite nord-ouest du cercle

de Kandi était constituée par «la limite Dahomey-colonie du Niger,
du fleuve Niger au confluent de la Pendjari avec le marigot Sud de
Kompongou»;

— l’arrêté local n° 1464 APA du gouverneur par intérim du Dahomey,

en date du 30 septembre 1937, fixant certaines conditions d’applica-
tion du décret du 13 octobre 1936 portant réglementation de la chasse

30 FRONTIER DISPUTE (JUDGMENT ) 116

the cercle of Djougou (Dahomey)” was formed, inter alia,by

“[t]he Altacora mountain range, whose summit it follows, or, more
precisely, a line parallel to the Konkobiri-Tandangou-Sangou trail
running along the foot of the mountain, at a distance of 8 km from

the trail”;
— a decree of 23 April 1913, Article 1 of which provided that “[t]he

boundary between the cercles of Fada-N’Gourma (Haut-Sénégal et
Niger) and Atacora (Dahomey)” was determined, inter alia,by

“a line parallel, in the east, to the Compongou-Konkobiri-Batch-
ango trail running along the foot of the Atacora mountain range at
a distance of 8 km from the trail and continuing until it meets the
upper course of the River Pendjari”;

— a decree of 1 March 1919 dividing the colony of Haut-Sénégal et
Niger and creating the colony of Haute-Volta;
—an arrêté général of 16 April 1926 laying down certain conditions for
the implementation of the decree of 10 March 1925 regulating hunt-

ing and creating game parks in the AOF;
—an arrêté général adopted by the Governor-General ad interim of the
AOF on 31 August 1927, fixing the boundaries of the colonies of
Haute-Volta and Niger. Although, as stated by its text, this arrêté
related to the frontier between Haute-Volta and Niger, it provided, in

Article 1, paragraph 2, that the boundaries between the cercle of Say
and Haute-Volta were formed

“[i]n the South-West, [by] a line starting approximately from the
[River] Sirba at the level of the Say parallel and running as far as
the Mekrou;
[i]n the South-East, by the Mekrou from that point as far as its
confluence with the Niger”.

This arrêté général was amended, on this point among others, by an
erratum of 5 October 1927, published in the Journal officiel of the

AOF of 15 October 1927, in which the final subparagraph of Article 1
provided simply that the boundary of the colonies of Niger and
Haute-Volta “follows . . . the course of the Tapoa upstream until it
meets the former boundary of the cercles of Fada and Say, which it
follows as far as its intersection with the course of the Mekrou”;
— the aforementioned arrêtés généraux of 8 December 1934 and

27 October 1938, which indicated, inter alia, that the north-western
boundary of the cercle of Kandi was formed by “the boundary
between Dahomey and the colony of Niger, from the River Niger to
the confluence of the Pendjari with the Kompongou southern
‘marigot’ ”;

— local arrêté No. 1464 APA of the Governor ad interim of Dahomey,
dated 30 September 1937, laying down certain conditions for the
implementation of the decree of 13 October 1936 regulating hunting

30117 DIFFÉREND FRONTALIER (ARRÊT )

dans les principaux territoires africains relevant du ministère des

colonies;
— l’arrêté local n° 1302/AE/SZ du gouverneur du Niger, en date du
13 novembre 1937, établissant que serait réservée sous l’appellation
«Parc national du W» une partie du territoire des cercles de Niamey
et de Fada N’Gourma;

— l’arrêté général n° 7640 SE/F du 3 décembre 1952, constituant en
«Réserve totale du W du Niger» une partie du cercle de Kandi
(Dahomey), dont il fixait les limites;
— l’arrêté général n° 4676 SE/F du 25 juin 1953, portant création de la
«Réserve totale de faune du W du Niger» dans une zone située dans

le cercle de Niamey (Niger), dont il fixait les limites.

Les Parties ont également débattu, à propos de la frontière dans le sec-
teur de la rivière Mékrou, de la portée de certains documents postérieurs
à la date des indépendances, notamment:

— la note verbale n° 03498 adressée le 29 août 1973 au ministère des
affaires étrangères du Dahomey par le ministère des affaires étran-
gères du Niger, au sujet de la réunion d’une commission paritaire
concernant un projet commun de barrage sur la rivière Mékrou;

— le procès verbal d’une réunion d’experts des Gouvernements du Niger
et du Dahomey, tenue le 8 février 1974, «au sujet de la Mékrou et du
projet de barrage à réaliser sur son cours»;
— l’accord du 14 janvier 1999 entre le Niger et le Bénin, relatif à la réa-
lisation de l’aménagement hydroélectrique au site de Dyodyonga sur

la rivière Mékrou.

*

40. Les Parties ont également produit, à l’appui de leurs thèses respec-

tives, un matériau cartographique et photographique volumineux, diver-
sifié tant par la date que par l’origine, la qualité technique et le degré de
précision.
41. En vue d’identifier le chenal principal du fleuve Niger et d’établir la
répartition des îles du fleuve entre les Parties, le Niger s’est fondé en par-

ticulier, parmi de nombreux autres cartes et croquis, sur: les cartes du
cours du Niger préparées en 1896 à la suite d’une mission, conduite par le
lieutenant de vaisseau Hourst, chargée d’étudier le régime du fleuve et sa
navigabilité; le plan général à l’échelle de 1/10000 de l’étude sur la navi-
gabilité du bief fluvial du Niger entre Niamey et Gaya effectuée par la

mission conduite par A. Beneyton en 1929-1930; la carte annexée au rap-
port sur la reconnaissance du fleuve entre Niamey et Malanville qui fut
effectuée en 1949 suivant un ordre de mission du chef des services de la
région Bénin-Niger; la feuille n° 4 de la mission d’étude sur la navigabi-
lité du fleuve (relevé des hauts-fonds à l’échelle de 1/10000) réalisée en

1965 par le serviceosopographique et du cadastre de la République du
Niger; les cartes n 32 à 37 à l’échelle de 1/50000 de l’étude sur la navi-

31 FRONTIER DISPUTE (JUDGMENT ) 117

in the principal African territories under the jurisdiction of the
Ministry of the Colonies;

— local arrêté No. 1302/AE/SZ of the Governor of Niger, dated
13 November 1937, providing that part of the territory of the cercles
of Niamey and Fada N’Gourma would be set aside for the “Niger W
National Park”;
— arrêté général No. 7640 SE/F of 3 December 1952, designating part

of the cercle of Kandi (Dahomey) as the “Niger W Total Reserve”,
the boundaries of which it fixed;
— arrêté général No. 4676 SE/F of 25 June 1953, creating the “Niger W
Total Game Reserve” in an area situated in the cercle of Niamey
(Niger), the boundaries of which it fixed.

The Parties also discussed, in connection with the frontier in the River
Mekrou sector, the significance of certain documents that are posterior to

the dates of independence, in particular:
— Note Verbale No. 03498, addressed on 29 August 1973 to the Minis-
try of Foreign Affairs of Dahomey by the Ministry of Foreign Affairs

of Niger, concerning the meeting of a joint committee regarding a
joint dam project on the River Mekrou;
— the minutes of a meeting of experts of the Governments of Niger and
Dahomey, held on 8 February 1974, “concerning the Mekrou and the
dam project on that river”;

— the Agreement of 14 January 1999 between Niger and Benin, relating
to the development of a hydroelectric facility at Dyodyonga on the
River Mekrou.

*

40. The Parties also produced a large quantity of cartographic and
photographic material in support of their respective arguments, varying
in date, origin, technical quality and level of accuracy.

41. With regard to the identification of the main channel of the River
Niger and the attribution of the islands in that river between the Parties,
Niger has relied in particular on the following, among many other maps
and sketch-maps: maps of the course of the Niger prepared in 1896 fol-
lowing a mission led by Lieutenant Commander Hourst to study the
régime of the river and its navigability; the general 1:10,000 plan from

the study on the navigability of the stretch of the Niger between Niamey
and Gaya carried out by the mission led by A. Beneyton in 1929-1930;
the map annexed to the report on the survey of the river between Niamey
and Malanville carried out in 1949 on the instructions of the chef des
services of the Benin-Niger region; sheet No. 4 of the study on the navi-

gability of the river (1:10,000 survey of the shoals) prepared in 1965 by
the topographic service and land registry of the Republic of Niger; maps
Nos. 32 to 37 on a scale of 1:50,000 from the study on the navigability of

31118 DIFFÉREND FRONTALIER (ARRÊT )

gabilité du fleuve Niger entre Tossaye et Yelwa, réalisée à partir de 1967

par l’entreprise néerlandaise NEDECO sur demande de quatre Etats rive-
rains du fleuve (Dahomey, Mali, Niger et Nigéria), dont les travaux sur le
terrain furent effectués en 1968-1969 et le rapport final produit en sep-
tembre 1970; et les feuilles nos 1à4àl’échellede1/50000del’étudedu
fleuve Niger établie en 1979 par l’Institut géographique national de

France (IGN) à partir d’une mission photographique effectuée en avril
1975. Le Niger a également signalé que les cartes de l’Afrique de l’Ouest
à l’échelle de 1/200000 éditées par le service cartographique de l’AOF à
Dakar en 1955 et 1960 faisaient courir la limite intercoloniale dans le
cours du fleuve.

Le Bénin s’est, pour sa part, référé au matériau cartographique datant
de l’époque coloniale, produit par l’une ou l’autre des Parties, afin de
démontrer que les cartographes n’auraient jamais tenu pour établi que la
limite entre les colonies du Dahomey et du Niger suivait le chenal navi-

gable du fleuve Niger. Par ailleurs, selon le Bénin, les croquis ou études
susmentionnés, invoqués par le Niger à l’appui de son argumentation, ne
permettraient pas d’établir le chenal navigable à la date des indépen-
dances ou l’appartenance des îles du fleuve à l’une ou l’autre des Parties.
Le Bénin invoque enfin une étude, réalisée aux fins de la présente affaire

par l’IGN-France international en décembre 2003, qui a effectué une
comparaison des cartes de la région publiées par l’IGN en 1960 avec
des images SPOT recueillies à la même échelle en 2002, pour montrer
les changements de la configuration du bras le plus large et des îles du
fleuve Niger au cours des cinquante dernières années.

42. S’agissant du secteur de la rivière Mékrou, chacune des Parties a
invoqué, à l’appui de sa position, plusieurs cartes datant de la période
coloniale.
Selon le Bénin, ces cartes (et notamment toutes celles réalisées après
1919, à l’exception d’une carte datée de 1922, et rééditée en 1928, dont

fait mention le Niger) confirment que la rivière constituait la limite inter-
coloniale; il se réfère notamment au matériau cartographique suivant: les
feuilles de «Kandi» et de «Niamey» de la carte (à l’échelle de 1/500000)
dressée et publiée en octobre 1926 par le service géographique de l’AOF
(connue sous le nom de «carte Blondel la Rougery»); la carte intitulée

«Nouvelle frontière de la Haute-Volta et du Niger (suivant erratum du
5 octobre 1927 à l’arrêté du 31 août 1927)» (à l’échelle de 1/1000000);
une carte sans date intitulée «Croquis de la colonie du Niger, dressé par
le colonel Abadie, de l’infanterie coloniale» (à l’échelle de 1/4500000);
une carte routière Dahomey-Togo (à l’échelle de 1/1000000) établie par

le service géographique de l’AOF en 1938; et un croquis routier intitulé
«Dahomey et Togo», préparé par ce même service en 1948.
Le Niger s’est appuyé sur un matériau cartographique abondant pour
montrer que les autorités coloniales n’auraient eu qu’une connaissance
approximative de la région de la rivière Mékrou, ainsi que du tracé exact

du cours de cette rivière, et que la limite établie par le décret du 2 mars
1907 n’aurait jamais été remise en cause; il a appelé à cet égard l’atten-

32 FRONTIER DISPUTE (JUDGMENT ) 118

the River Niger between Tossaye and Yelwa conducted from 1967
onwards by NEDECO, a Dutch firm, at the request of four riparian

States (Dahomey, Mali, Niger and Nigeria), the work on the ground
being carried out in 1968-1969 and the final report produced in Septem-
ber 1970; and sheets Nos. 1 to 4 on a scale of 1:50,000 from the study of
the River Niger in 1979 by the French Institut géographique national
(IGN) on the basis of a photographic mission in April 1975. Niger also

pointed out that the 1:200,000 maps of West Africa published by the
AOF cartographic service in Dakar in 1955 and 1960 situated the inter-
colonial boundary in the course of the river.

For its part, Benin has referred to cartographic material dating from

the colonial period, produced by one or other of the Parties, to demon-
strate that the cartographers never took it for granted that the boundary
between the colonies of Dahomey and Niger followed the navigable
channel of the River Niger. Moreover, according to Benin, the above-
mentioned sketch-maps or studies, relied on by Niger in support of its
argument, cannot be used to define the navigable channel at the dates of

independence or to determine to which of the Parties the islands in the
river belong. Finally, Benin relies on a study carried out for the purposes
of the present case by IGN-France international in December 2003,
which compared the maps of the region published by IGN in 1960 with
SPOT images on the same scale recorded in 2002, in order to show the

changes in the configuration of the widest channel and islands of the
River Niger over the last 50 years.
42. With regard to the River Mekrou sector, each Party has relied on
several maps dating from the colonial period to support its position.

According to Benin, these maps (in particular those prepared after
1919, with the exception of a map dated 1922 and republished in 1928
cited by Niger) confirm that the Mekrou was the intercolonial boundary.
Benin refers, inter alia, to the following cartographic documentation: the
“Kandi” and “Niamey” sheets of the map (1:500,000) prepared and pub-

lished in October 1926 by the AOF Geographical Service (known as the
“Blondel la Rougery map”); the map entitled “New Boundary of Haute-
Volta and Niger (according to the erratum of 5 October 1927 to the
arrêté of 31 August 1927)” (1:1,000,000); an undated map entitled
“Sketch-map of the Colony of Niger prepared by Colonel Abadie of
the Colonial Infantry” (1:4,500,000); a Dahomey-Togo road map

(1:1,000,000) prepared by the AOF Geographical Service in 1938; and a
road sketch-map entitled “Dahomey and Togo” prepared by the same
service in 1948.
Niger has relied on a large amount of cartographic material to show
that the colonial authorities had only a vague knowledge of the River

Mekrou region and of the exact course of that river, and that the bound-
ary established by the decree of 2 March 1907 had never been challenged;
in this connection, it drew the attention of the Chamber to a combined

32119 DIFFÉREND FRONTALIER (ARRÊT )

tion de la Chambre sur une carte d’ensemble politique et administrative
de l’AOF éditée en 1928 (version actualisée d’une carte de même objet

établie en 1922), où les dates du 2 mars 1907 et du 6 septembre 1909 figu-
raient le long de la ligne marquant la limite dans le secteur de la Mékrou.
43. Les Parties se réfèrent enfin à certaines cartes pour déterminer les
coordonnées indicatives de points précis de leur frontière commune.
Le Bénin mesure ainsi les coordonnées des points triples avec le Bur-

kina Faso et le Nigéria sur la base des feuilles pertinentes de la carte qu’il
considère comme étant la carte la plus fiable publiée à la veille des indé-
pendances, à savoir une carte de l’AOF à l’échelle de 1/200000 établie par
l’IGN en 1955.
Le Niger a quant à lui indiqué que les coordonnées du point double

Bénin/Niger et du point triple avec le Burkina Faso qu’il revendique dans
le secteur de la rivière Mékrou ont été relevées sur les cartes de l’IGN à
l’échelle de 1/200000 (la feuille de Kandi d’une carte de l’Afrique de
l’Ouest publiée par l’IGN étant annexée à son mémoire).
44. La Chambre rappellera ici les termes dans lesquels la valeur pro-
bante des cartes a été précisée dans l’arrêt rendu en l’affaire du Différend

frontalier (Burkina Faso/République du Mali) :

«les cartes ne sont que de simples indications, plus ou moins exactes
selon les cas; elles ne constituent jamais — à elles seules et du seul
fait de leur existence — un titre territorial, c’est-à-dire un document
auquel le droit international confère une valeur juridique intrinsèque
aux fins de l’établissement des droits territoriaux. Certes, dans

quelques cas, les cartes peuvent acquérir une telle valeur juridique
mais cette valeur ne découle pas alors de leurs seules qualités intrin-
sèques: elle résulte de ce que ces cartes ont été intégrées parmi les élé-
ments qui constituent l’expression de la volonté de l’Etat ou des Etats
concernés. Ainsi en va-t-il, par exemple, lorsque des cartes sont

annexées à un texte officiel dont elles font partie intégrante. En
dehors de cette hypothèse clairement définie, les cartes ne sont que
des éléments de preuve extrinsèques, plus ou moins fiables, plus ou
moins suspects, auxquels il peut être fait appel, parmi d’autres élé-
ments de preuve de nature circonstancielle, pour établir ou reconsti-

tuer la matérialité des faits.» (C.I.J. Recueil 1986, p. 582, par. 54.)

En d’autres mots,
«hormis l’hypothèse où elles sont intégrées parmi les éléments qui

constituent l’expression de la volonté de l’Etat les cartes ne peuvent
à elles seules être considérées comme des preuves d’une frontière car
elles constitueraient dans ce cas une présomption irréfragable, équi-
valant en réalité à un titre juridique. Elles n’ont de valeur que
comme preuves à caractère auxiliaire ou confirmatif, ce qui exclut

également la possibilité de leur conférer la qualité de présomptions
juris tantum ou réfragables, ayant pour effet de renverser le fardeau
de la preuve.» (Ibid., p. 583, par. 56.)

33 FRONTIER DISPUTE (JUDGMENT ) 119

political and administrative map of the AOF published in 1928 (the
updated version of a similar map prepared in 1922) on which the dates of

2 March 1907 and 6 September 1909 are placed along the line marking
the boundary in the Mekrou sector.
43. Finally, the Parties refer to certain maps in order to determine the
indicative co-ordinates of precise points on their common frontier.
Thus Benin measures the co-ordinates of the tripoints with Burkina

Faso and Nigeria on the basis of the relevant sheets of what it regards as
the most reliable map published on the eve of the independence of the
two States, namely a 1:200,000 map of the AOF produced by the IGN in
1955.
Niger has noted that the co-ordinates of the Benin/Niger bipoint and

of the tripoint with Burkina Faso that it claims in the River Mekrou sec-
tor were plotted on 1:200,000 IGN maps (the Kandi sheet of a map of
West Africa published by the IGN which is annexed to its Memorial).

44. The Chamber would recall here the terms in which the probative
value of maps was described in the Judgment rendered in the case con-

cerning the Frontier Dispute (Burkina Faso/Republic of Mali ):

“maps merely constitute information which varies in accuracy from
case to case; of themselves, and by virtue solely of their existence,
they cannot constitute a territorial title, that is, a document endowed
by international law with intrinsic legal force for the purpose of
establishing territorial rights. Of course, in some cases maps may

acquire such legal force, but where this is so the legal force does not
arise solely from their intrinsic merits: it is because such maps fall
into the category of physical expressions of the will of the State or
States concerned. This is the case, for example, when maps are
annexed to an official text of which they form an integral part.

Except in this clearly defined case, maps are only extrinsic evidence
of varying reliability or unreliability which may be used, along with
other evidence of a circumstantial kind, to establish or reconstitute
the real facts.” (I.C.J. Reports 1986, p. 582, para. 54.)

In other words,
“except when the maps are in the category of a physical expression

of the will of the State, they cannot in themselves alone be treated as
evidence of a frontier, since in that event they would form an irre-
buttable presumption, tantamount in fact to legal title. The only
value they possess is as evidence of an auxiliary or confirmatory
kind, and this also means that they cannot be given the character of

a rebuttable or juris tantum presumption such as to effect a reversal
of the onus of proof.” (Ibid., p. 583, para. 56.)

33120 DIFFÉREND FRONTALIER (ARRÊT )

Ce principe guidera également l’appréciation par la Chambre des
cartes invoquées par les Parties en l’espèce.

*
* *

45. La Chambre est tout d’abord invitée, selon les termes des alinéas
a) et b) de l’article 2 du compromis, à déterminer le tracé de la frontière
dans le secteur du fleuve Niger, puis à préciser à laquelle des Parties
appartient chacune des îles dudit fleuve.

Ainsi que la Chambre l’a rappelé (voir paragraphe 23 ci-dessus), les
Parties lui ont expressément demandé de s’acquitter de sa tâche en appli-
quant, en particulier, le principe de la succession des Etats aux frontières
héritées de la colonisation, à savoir le principe de l’intangibilité desdites
frontières, ou encore principe de l’uti possidetis juris.

46. En la présente instance, ces limites territoriales n’étaient rien de
plus que des délimitations entre différentes divisions administratives ou
colonies relevant de la même autorité coloniale. Ce n’est qu’au moment
de l’indépendance, autrement dit de la «date critique», que ces limites

sont devenues des frontières internationales. Auparavant, la question de
la délimitation était régie par le droit colonial français, ou «droit d’outre-
mer». Ainsi qu’il a été relevé plus haut (voir paragraphe 28), dans l’appli-
cation du principe de l’uti possidetis juris, le droit français n’intervient
pas en tant que tel, mais seulement comme un élément de fait parmi

d’autres, ou comme moyen de preuve et de démonstration concernant ce
que l’on a pu appeler le «legs colonial» à la date critique.
Les Parties ayant accédé à l’indépendance quasiment à la même
époque (voir paragraphe 20 ci-dessus), la période comprise entre le 1 er
et le 3 août 1960 peut être retenue comme date critique.

47. Conformément à la démarche adoptée par la Chambre en l’affaire
du Différend frontalier (Burkina Faso/République du Mali) , la Chambre
commencera par examiner les divers actes réglementaires ou adminis-
tratifs invoqués par les Parties; en effet, aux fins de l’établissement de la

souveraineté, le titre juridique l’emporte sur la possession effective
(C.I.J. Recueil 1986, p. 586-587, par. 63).
A cet égard, il convient de le rappeler, les Parties s’accordent à recon-
naître que, durant la période considérée, la création de colonies ou de ter-
ritoires releva, jusqu’en 1946, de la compétence du président de la Répu-

blique française, puis de celle du Parlement français, la création de
subdivisions coloniales relevant quant à elle, aux termes du décret du
18 octobre 1904, de celle du gouverneur général de l’AOF. Dans sa
circulaire n 114c du 3 novembre 1912, le gouverneur général de l’AOF

précisa que les principales subdivisions («cercles») seraient déterminées
par le gouverneur général, mais que les lieutenants-gouverneurs seraient
habilités à créer de nouvelles subdivisions territoriales à l’intérieur
des «cercles» (voir paragraphe 30 ci-dessus).
La Chambre note que les Parties s’accordent également à reconnaître

que la compétence de créer ou d’établir des entités territoriales incluait le

34 FRONTIER DISPUTE (JUDGMENT ) 120

This principle will also guide the Chamber in its assessment of the
maps relied on by the Parties in the present case.

* * *

45. The Chamber is firstly asked, in accordance with Article 2, para-
graphs (a) and (b), of the Special Agreement, to determine the course of

the boundary in the sector of the River Niger and then to specify to
which Party each of the islands in the river belongs.
As the Chamber has recalled (see paragraph 23 above), the Parties
have expressly asked it to carry out its task on the basis of, in particular,
the principle of the succession of States to the frontiers inherited from

colonialism, namely the principle of the intangibility of such frontiers,
also known as the principle of uti possidetis juris.
46. In the present case these territorial boundaries were no more than
delimitations between different administrative divisions or colonies sub-
ject to the same colonial authority. Only at the moment of independence,
also called the “critical date”, did these boundaries become international

frontiers. Until that time the matter of delimitation was governed by
French colonial law, known as “droit d’outre-mer”. As noted above (see
paragraph 28), in the application of the principle of uti possidetis juris,
French law does not play a role in itself but only as one factual element
among others, or as evidence indicative of what has been called the

“colonial heritage” at the critical date.

Since the Parties achieved independence virtually simultaneously (see
paragraph 20 above), the period between 1 and 3 August 1960 can be
considered as the critical date.

47. In accordance with the approach of the Chamber in the Frontier
Dispute (Burkina Faso/Republic of Mali) case, the Chamber will first
consider the various regulative or administrative acts invoked by the
Parties; thus, pre-eminence is to be accorded to legal title over effective
possession as a basis of sovereignty (I.C.J. Reports 1986, pp. 586-587,

para. 63).
In this respect, it is relevant to recall that the Parties agree that, during
the period under consideration, the power to create colonies or territories
was vested in the President of the French Republic until 1946 and
thereafter in the French Parliament, while colonial subdivisions could
be created by the Governor-General of the AOF under the terms of

the decree of 18 October 1904. In his circular No. 114c of 3 November
1912, the Governor-General of the AOF determined that the main
subdivisions (“cercles”) would be established by the Governor-General,
but that the Lieutenant-Governors would be entitled to create further
territorial subdivisions within the “cercles” (see paragraph 30 above).

It appears that it is not disputed between the Parties that the compe-
tence to create or establish territorial entities included the power to deter-

34121 DIFFÉREND FRONTALIER (ARRÊT )

pouvoir d’en déterminer l’étendue et les limites, bien que, durant la
période coloniale, ce principe n’ait jamais été rendu explicite dans aucun

acte réglementaire ou administratif.

**

48. Ainsi que la Chambre l’a exposé ci-dessus (voir paragraphes 32
à 36), la colonie du Dahomey fut créée par décret du 22 juin 1894 et inté-
grée à l’AOF par décret du 17 octobre 1899. Il n’est pas contesté que,

durant cette période, la colonie du Dahomey englobait des territoires
situés sur les deux rives du fleuve Niger.
49. Par arrêté du 23 juillet 1900, le gouverneur général de l’AOF éta-
blit un troisième territoire militaire, appelé à «s’étendr[e] sur les régions
de la rive gauche du Niger de Say au lac Tchad qui [avaient] été placées

dans la sphère d’influence française par la convention [anglo-française]
du 14 juin 1898».
50. Le 20 décembre 1900, un décret du président de la République
française fut promulgué, établissant un troisième territoire militaire «entre
le Niger et le Tchad». Le décret, supérieur à un arrêté dans la hiérarchie
des actes juridiques, ne contenait pas de référence à l’arrêté du

23 juillet 1900. De l’avis de la Chambre, le décret n’en doit pas moins être
considéré comme venant confirmer l’arrêté du gouverneur général; il
couvre, quoique en termes moins précis, la même zone située entre le
(fleuve) Niger et le (lac) Tchad.

*

51. Le Bénin soutient que l’arrêté du 23 juillet 1900 fixait la limite
entre le troisième territoire militaire et la colonie du Dahomey sur la rive
gauche du fleuve Niger. Selon lui, les zones situées au-delà de la rive
gauche ayant été dissociées du Dahomey, le fleuve lui-même et ses îles
sont demeurés partie intégrante de cette colonie. Il soutient également

que la limite ainsi établie fut confirmée en 1954 par M. Raynier, secrétaire
général et gouverneur par intérim du Niger, dans sa lettre du 27 août
(voir paragraphe 38 ci-dessus).
52. Le Niger, pour sa part, conteste que l’arrêté du 23 juillet 1900 ait
fixé une limite; selon lui, le libellé pertinent visait simplement à indiquer
l’étendue géographique du territoire nouvellement créé. Il fait aussi obser-

ver qu’une entente ne tarda pas à se dégager, selon laquelle la limite était
située sur «le cours du fleuve», ce qui ne pouvait que signifier qu’elle se
trouvait dans le lit du fleuve. Pour prouver l’existence de cette entente, le
Niger fait état d’une lettre du ministre français des colonies en date du
7 septembre 1901 (voir paragraphe 38 ci-dessus). Il soutient aussi que

cette entente fut confirmée officiellement dans deux arrêtés du gouver-
neur général de l’AOF, des 8 décembre 1934 et 27 octobre 1938.

35 FRONTIER DISPUTE JUDGMENT ) 121

mine their extent and to delimit them, although during the colonial
period this was never made explicit in any regulative or administrative

act.

**

48. As the Chamber has set out above (see paragraphs 32 to 36), the
colony of Dahomey was created by decree of 22 June 1894 and incorpo-
rated into the AOF by decree of 17 October 1899. It is not contested that,

during this period, the colony of Dahomey comprised territories situated
on both banks of the River Niger.
49. By arrêté of 23 July 1900 the Governor-General of the AOF estab-
lished a Third Military Territory, which “will encompass the areas on the
left bank of the Niger between Say and Lake Chad that were placed

within the French sphere of influence by the [Anglo-French] Convention
of 14 June 1898”.
50. On 20 December 1900 a decree of the President of the French
Republic was issued which established a Third Military Territory
“between the Niger and Lake Chad”. The decree, which was superior to
an arrêté in the hierarchy of legal acts, made no reference to the arrêté of

23 July 1900. In the Chamber’s view, the decree must nevertheless be seen
as a confirmation of the arrêté of the Governor-General; it covers, albeit
in less precise terms, the same area between (the River) Niger and (Lake)
Chad.

*

51. Benin contends that the arrêté of 23 July 1900 established the
boundary between the Third Military Territory and the colony of Daho-
mey at the left bank of the River Niger. According to Benin, by detach-
ing the areas beyond the left bank from Dahomey, the river itself and the
islands located therein remained part of that colony. Benin further con-

tends that the boundary thus established was confirmed in 1954 by
Mr. Raynier, Secretary-General and Governor ad interim of Niger, in his
letter of 27 August (see paragraph 38 above).
52. Niger, for its part, denies that the arrêté of 23 July 1900 estab-
lished a boundary; in its view the relevant wording was merely intended
to indicate the territorial extent of the newly created Territory. It further

observes that an understanding soon developed that the boundary was
constituted by “the course of the river” and that this could only mean
that the boundary was situated within the watercourse of the river. As
evidence of this understanding, Niger refers to a letter of the French Min-
ister for the Colonies dated 7 September 1901 (see paragraph 38 above).

It further contends that this understanding was formally confirmed in
two arrêtés of the Governor-General of the AOF of 8 December 1934
and 27 October 1938.

35122 DIFFÉREND FRONTALIER (ARRÊT )

Le croquis n° 3, à la page 123 ci-après, illustre les revendications des
Parties en ce qui concerne la frontière dans le secteur du fleuve Niger.

*

53. De l’avis de la Chambre, on ne saurait considérer l’arrêté du
23 juillet 1900 et le décret du 20 décembre 1900, créant à eux deux le troi-

sième territoire militaire, comme fixant les limites de celui-ci. Les réfé-
rences géographiques employées ne peuvent être envisagées que comme
servant à délimiter d’une manière générale le territoire nouvellement
créé; les expressions «les régions de la rive gauche du Niger» et «le
Niger», figurant respectivement dans l’arrêté et dans le décret, montrent

clairement que ces zones sont alors dissociées de la colonie du Daho-
mey, à laquelle elles appartenaient précédemment.
54. La conclusion selon laquelle les instruments juridiques des 23 juillet
et 20 décembre 1900 ne fixaient pas de limite et n’étaient pas considérés à
l’époque comme le faisant est confirmée par la lettre du ministre français
des colonies au gouverneur général de l’AOF en date du 7 septembre

1901. Dans cette lettre, il est fait référence à deux rapports politiques,
dans lesquels le gouverneur du Dahomey indique, à propos de la délimi-
tation entre le Dahomey et le troisième territoire militaire, que «le cours
du Niger» constituerait la meilleure ligne de démarcation, au double
point de vue géographique et politique, suggestion apparemment appuyée

par le gouverneur général puisque, dans sa réponse, le ministre écrit qu’il
«partage sur ce point [la] manière de voir» du gouverneur général.
55. Bien que cette lettre ne fixe pas de limite, la Chambre estime qu’elle
représente un moyen de preuve suffisant pour établir qu’il n’y avait pas
eu de délimitation l’année précédente. La Chambre n’a pas davantage

trouvé de document indiquant qu’une limite aurait été fixée au cours des
années suivantes. Elle relève à ce propos qu’une version préparatoire de
l’arrêté général du 23 novembre 1912 sur la réorganisation administrative
interne du territoire militaire du Niger prévoyait la possibilité de situer la
limite sur la rive droite du fleuve Niger, attribuant ainsi toutes les îles du

fleuve à ce territoire, mais que cette proposition ne fut pas retenue dans
l’arrêté lui-même, qui ne contenait pas de clause de délimitation.
56. La Chambre conclut donc qu’elle ne saurait accueillir la thèse du
Bénin selon laquelle l’arrêté du 23 juillet 1900 situait la limite sur la rive
gauche du fleuve Niger, délimitation qui serait demeurée en vigueur
jusqu’à la date de l’indépendance.

**

57. Ainsi qu’il a été indiqué plus haut (voir paragraphe 51), le Bénin
soutient que la limite établie par l’arrêté du 23 juillet 1900 fut confirmée

dans une lettre de M. Raynier, gouverneur par intérim du Niger, en date
du 27 août 1954. Dans cette lettre, M. Raynier informait le chef de la
subdivision de Gaya (Niger) que «la limite du territoire du Niger [était]

36 FRONTIER DISPUTE (JUDGMENT ) 122

Sketch-map No. 3, on page 123 below, shows the claims of the Parties
in respect of the boundary in the sector of the River Niger.

*

53. The Chamber is of the view that the arrêté of 23 July 1900 in con-
junction with the decree of 20 December 1900, which created the Third

Military Territory, cannot be read as determining the boundaries thereof.
The geographical references used can only be seen as indicating in general
terms the extent of the newly created territory; the words “the areas on
the left bank of the Niger” in the arrêté and “the Niger” in the decree
make it clear that these areas are detached from the colony of Dahomey

to which they previously belonged.

54. The conclusion that the legal instruments of 23 July and 20 Decem-
ber 1900 did not determine any boundary, and were not considered at the
time as doing so, is confirmed by the letter of 7 September 1901 of the
French Minister for the Colonies addressed to the Governor-General of

the AOF. In this letter reference is made to two political reports in which
the Governor of Dahomey indicated with regard to the delimitation
between Dahomey and the Third Military Territory that “the course of
the Niger” would constitute the best demarcation line, both from a geo-
graphical and a political point of view. The Governor-General appar-

ently supported this suggestion and in his reply the Minister wrote that
he “share[d] [the] view [of the Governor-General] on this point”.
55. Although this letter did not determine the boundary, the Chamber
considers that it provides sufficient evidence that a delimitation had not
taken place the year before. Nor has the Chamber found any document

which shows that a delimitation was carried out in subsequent years. The
Chamber notes in this respect that a preparatory draft of the arrêté
général of 23 November 1912 on the internal administrative reorganiza-
tion of the Military Territory of Niger contained a suggestion to locate
the boundary at the right bank of the River Niger, thus allocating all

islands in the river to this Territory, but that this proposal was not fol-
lowed in the arrêté itself which did not contain any delimitation clause.
56. The Chamber therefore concludes that Benin’s argument that the
arrêté of 23 July 1900 located the boundary at the left bank of the River
Niger, and that this delimitation remained in force until the date of
independence, cannot be upheld.

**

57. As noted above (see paragraph 51), Benin contends that the bound-
ary as established in the arrêté of 23 July 1900, was confirmed in a letter

of Mr. Raynier, Governor ad interim of Niger, of 27 August 1954. In this
letter, Mr. Raynier informed the chef of the subdivision of Gaya (Niger)
that “the boundary of the territory of Niger [was] constituted by the

36123 DIFFÉREND FRONTALIER (ARRÊT )FRONTIER DISPUTE (JUDGMENT ) 123124 DIFFÉREND FRONTALIER (ARRÊT )

constituée de la ligne des plus hautes eaux, côté rive gauche du fleuve à

partir du village de Bandofay, jusqu’à la frontière d[u] Nigéria» et que,
«[e]n conséquence, toutes les îles situées dans cette partie du fleuve [fai-
saient] partie du territoire du Dahomey.»
58. D’après le Bénin, cette lettre confirme l’existence de la limite sur la
rive gauche et précise qu’elle est constituée par «la ligne des plus hautes

eaux». Le Bénin fait valoir que l’auteur de cette lettre n’a nullement
outrepassé les compétences qui étaient les siennes en tant que lieutenant-
gouverneur, et que ce texte doit être considéré comme ayant un caractère
déclaratoire dans la mesure où il confirme et précise un titre préexistant,
et un caractère constitutif dans la mesure où il explicite ce titre.

59. Le Bénin soutient en outre que le Niger est lié par cette lettre,
celle-ci ayant par la suite fait l’objet d’une correspondance intercoloniale,
sur laquelle les autorités du Dahomey se sont fondées. La lettre n’a
jamais été désavouée par son auteur, ni invalidée par une autorité supé-

rieure. De l’avis du Bénin, «[a]ux fins de l’application du principe de l’uti
possidetis, ce sont donc bien les échanges de correspondance de 1954 qui
constituent «le legs colonial», c’est-à-dire l’instantané territorial à la date
critique».
60. Le Niger conteste que M. Raynier ait été compétent pour établir

une limite intercoloniale et considère donc que la lettre est dénuée de tout
fondement juridique. Il soutient également que la lettre ne portait que sur
une portion de la limite (entre Bandofay et la frontière avec le Nigéria), et
qu’elle ne saurait donc en déterminer l’intégralité. Le Niger affirme enfin
que la lettre avait un caractère intracolonial et qu’elle n’a jamais conduit

à une entente intercoloniale susceptible d’être invoquée de bonne foi.

**

61. La Chambre examinera tout d’abord le contexte dans lequel fut

rédigée la lettre du 27 août 1954.
Il ressort du dossier que, au cours de la première moitié de l’année 1954,
des difficultés s’étaient fait jour entre les autorités locales des deux colo-
nies sur la question du statut juridique de certaines îles du fleuve.
S’agissant de l’une d’entre elles («l’île en face de Gaya»), le comman-

dant du cercle de Kandi (Dahomey) adressa, le 17 juin 1954, une lettre au
gouverneur du Dahomey, lui demandant à qui appartenait cette île. Le
23 juillet de cette même année, le chef de la subdivision de Gaya (Niger)
adressa une demande plus générale au gouverneur du Niger, sollicitant
«tous renseignements utiles sur les îles du fleuve appartenant au Niger ou

au Dahomey». er
62. Dans sa réponse du 1 juillet 1954 à la première lettre, le gouver-
neur du Dahomey indiqua que «les arrêtés ayant délimité la frontière
entre ces deux territoires [étaient] muets» sur la question de l’attribution
des îles à chacune des colonies. Il priait le commandant du cercle de

Kandi d’établir la liste des îles dont le statut risquait d’entraîner des
litiges, «pour [lui] permettre de régler une fois pour toutes avec le

38 FRONTIER DISPUTE (JUDGMENT ) 124

line of highest water, on the left bank of the river, from the village of
Bandofay to the frontier of Nigeria”, and that “[c]onsequently, all the

islands situated in this part of the river [formed] part of the territory of
Dahomey”.
58. According to Benin, this letter both corroborates the existence of
the boundary at the left bank and adds the further precision that it is
constituted by “the line of highest water”. Benin argues that this was not

beyond the competence of a Lieutenant-Governor; the letter must be
deemed to be declaratory in so far as it confirmed and clarified an already
existing title and constitutive in so far as it contained a specification of
that title.
59. Benin further contends that Niger is bound by the letter since it

subsequently became the subject of intercolonial correspondence and was
relied upon by the authorities of Dahomey. The letter was never with-
drawn by its author nor was it invalidated by a higher authority. In
Benin’s view, “for the purposes of applying the uti possidetis principle,
it is thus indeed the 1954 correspondence which constitutes the ‘colonial
heritage’, that is to say, the ‘photograph’ of the territory at the critical

date”.
60. Niger denies that Mr. Raynier was competent to determine an
intercolonial boundary and consequently considers that the letter lacks
any legal basis. It further contends that the letter only refers to one sec-
tion of the limit (between Bandofay and the border with Nigeria) and

therefore cannot determine the whole boundary. Niger finally asserts that
the letter was of an intra-colonial character and never led to an inter-
colonial understanding to which it could be held in good faith.

**

61. The Chamber will first analyse the context in which the letter of
27 August 1954 was written.
From the case file it is clear that in the first half of 1954 difficulties had
arisen between the local authorities in the two colonies about the legal

status of certain islands in the river.
With regard to one of these islands, (“the island opposite Gaya”), the
commandant of the cercle of Kandi (Dahomey) sent a letter dated 17 June
1954 to the Governor of Dahomey asking to whom that island belonged.
On 23 July of the same year the chef of the subdivision of Gaya (Niger)
addressed a more general request to the Governor of Niger, asking for

“all relevant information regarding the islands in the river belonging to
Niger or to Dahomey”.
62. In his response of 1 July 1954 to the first letter, the Governor of
Dahomey stated that “the arrêtés delimiting the boundary between these
two territories [were] silent” on the question of the attribution of the

islands to each colony. He requested the commandant of the cercle of
Kandi to draw up a list of those islands, the status of which could be the
source of dispute, “in order to enable [him] to settle once and for all with

38125 DIFFÉREND FRONTALIER (ARRÊT )

Niger, [qu’il entendait saisir] de la question, ce problème de délimitation

de la frontière».
63. Dans sa réponse à la demande du chef de la subdivision de Gaya,
le gouverneur par intérim du Niger, M. Raynier (qui était arrivé à
Niamey le 25 août 1954), fournit, par lettre en date du 27 août 1954, les
précisions précédemment citées (voir paragraphe 57), sans toutefois les

assortir d’aucun motif ni faire référence à un quelconque acte réglemen-
taire ou administratif antérieur. Le commandant du cercle de Dosso
(dont relevait Gaya) communiqua une copie de cette lettre au comman-
dant du cercle de Kandi, lequel la transmit ensuite au gouverneur du
Dahomey.

64. Le 11 décembre 1954, le gouverneur du Dahomey demanda à son
homologue du Niger «de bien vouloir [lui] indiquer les références des
textes ou accords déterminant [les] limites» précisées dans sa lettre du
27 août. Il expliqua qu’il demandait ces éclaircissements «[a]fin de pou-

voir régler cette question sur le plan formol», étant donné que «[l]es
archives du Dahomey et l’arrêté général n 3578/AP du 27 octobre 1938
ne fourniss[aient] aucune précision à ce sujet».
Le gouverneur par intérim du Niger ne répondit jamais à cette demande.

*

65. La Chambre a déjà indiqué que l’arrêté du 23 juillet 1900 n’éta-
blissait aucune limite et que, par conséquent, la lettre du 27 août 1954 ne
pouvait être considérée comme une confirmation autorisée d’une telle

limite.
La Chambre relève en outre que, en droit colonial français, le lieute-
nant-gouverneur d’une colonie n’avait pas compétence pour déterminer
unilatéralement les limites extérieures de celle-ci. Par conséquent, le Bénin
n’est pas fondé à invoquer cette lettre en tant que titre juridique fixant la

limite à la rive gauche du fleuve.
66. La limite telle que définie dans la lettre aurait pu être validée par
une autorité supérieure, et c’est dans une telle perspective que le gouver-
neur du Dahomey demanda un complément d’information dans sa lettre
en date du 11 décembre 1954. Toutefois, cette lettre du 11 décembre 1954

demeura sans réponse. Par ailleurs, aucune des deux colonies ne prit de
mesure aux fins de faire valider par le gouverneur général de l’AOF la
limite indiquée dans la lettre du 27 août 1954. La Chambre ne saurait dès
lors accueillir la prétention du Bénin selon laquelle la lettre du
27 août 1954 constituerait, avec l’arrêté du 23 juillet 1900, un titre juri-

dique fixant la frontière à la rive gauche du fleuve.
67. S’agissant de la prétention du Bénin selon laquelle la lettre aurait
été à l’origine d’une sorte d’accord intercolonial informel liant le Niger à
la date critique de 1960, la Chambre note qu’un tel concept juridique
n’existait pas en droit colonial français ou «droit d’outre-mer» et qu’il ne

saurait dès lors conférer un titre au Bénin.
La Chambre a toutefois conscience que la lettre du 27 août 1954 a pu

39 FRONTIER DISPUTE (JUDGMENT ) 125

Niger, [with whom he intended to raise] the question, this problem of the
boundary delimitation”.

63. In his reply, dated 27 August 1954, to the request made by the chef
of the subdivision of Gaya, Mr. Raynier, the Governor ad interim of
Niger (who had arrived in Niamey on 25 August 1954), made the state-
ment referred to above (see paragraph 57). No reasoning was given nor
were any references made to earlier regulative or administrative acts. The

commandant of the cercle of Dosso (to which Gaya belonged) sent a copy
of this letter to the commandant of the cercle of Kandi, who in turn trans-
mitted it to the Governor of Dahomey.

64. On 11 December 1954 the Governor of Dahomey asked his counter-

part in Niger “to kindly provide [him] with particulars of the instru-
ments or agreements determining [the] boundaries” mentioned in the
letter of 27 August. The Governor stated that he sought this clarifi-
cation “in order that this question might be officially resolved” since
“Dahomey’s archives and arrêté général No. 3578/AP of 27 October
1938 provide[d] no specific information on the matter”.

The Governor ad interim of Niger never responded to that request.

*
65. The Chamber has already found that the arrêté of 23 July 1900 did

not establish a boundary; consequently, the letter of 27 August 1954 can-
not be seen as an authoritative confirmation of such a boundary.

The Chamber further notes that, under French colonial law, the
Lieutenant-Governor of a colony had no competence to unilaterally

delimit the external boundaries of the colony. The letter in itself cannot,
therefore, be relied on by Benin as a legal title placing the boundary on
the left bank of the river.
66. The boundary defined in the letter could have been validated by a
higher authority and it was with that in mind that the Governor of Daho-

mey asked for further information in his letter of 11 December 1954.
However, the letter of 11 December 1954 went unanswered. Moreover,
no further action was taken by either of the two colonies in order to have
the boundary indicated in the letter of 27 August 1954 validated by the
Governor-General of the AOF. The Chamber therefore cannot uphold
Benin’s claim according to which the letter of 27 August 1954 in conjunc-

tion with the arrêté of 23 July 1900 provides it with legal title to a bound-
ary on the left bank.
67. With regard to Benin’s contention that the letter led to some sort
of informal intercolonial understanding which bound Niger at the critical
date in 1960, the Chamber observes that such a legal concept did not

exist in French colonial law or “droit d’outre-mer” thus cannot provide
Benin with title.
The Chamber is, however, aware of the fact that the letter of 27 August

39126 DIFFÉREND FRONTALIER (ARRÊT )

produire certaines effectivités. Cette éventualité sera examinée ultérieure-
ment.

**

68. La Chambre examinera à présent les actes invoqués par le Niger
comme preuve de son titre juridique, à savoir les arrêtés pris par le gou-

verneur général de l’AOF le 8 décembre 1934 et le 27 octobre 1938, les-
quels portent réorganisation de la structure administrative interne de la
colonie du Dahomey et offrent une description des limites des différents
cercles. Dans les deux arrêtés, la limite nord-ouest du cercle de Kandi est
décrite comme étant constituée par «le cours du Niger jusqu’à son

confluent avec la Mékrou».
69. D’après le Niger, ces arrêtés sont la confirmation officielle et auto-
risée de ce que la limite entre le Dahomey et la colonie voisine du Niger
était située à l’intérieur même du cours d’eau, tel qu’indiqué dans la lettre
du ministre des colonies en date du 7 septembre 1901. Ces arrêtés suffi-
raient dès lors à prouver le titre du Niger, même si ce titre ne figure

expressément dans aucun acte réglementaire ou administratif antérieur.

70. Le Bénin soutient que ces arrêtés n’étaient que des actes de nature
intracoloniale et n’étaient pas destinés à définir une limite entre le Daho-
mey et une autre colonie. Il ajoute que la formulation en est imprécise et

n’exclut pas la possibilité que la frontière ait pu être fixée sur la rive
gauche du fleuve.

*

71. La Chambre relève tout d’abord que les deux arrêtés ont été pris
par le gouverneur général, autorité compétente pour établir, délimiter et
réorganiser les cercles des colonies. Dans la mesure où ils offrent une des-
cription des limites entre ces cercles et les colonies voisines relevant éga-
lement de son autorité, ces arrêtés n’ont pas un caractère exclusivement

interne et peuvent aussi être invoqués dans le cadre de relations inter-
coloniales. Aussi peut-on conclure, en vertu de ces arrêtés, que le cours
du fleuve Niger constituait la limite intercoloniale.
72. La Chambre n’est toutefois pas en mesure de déduire de ce qui pré-
cède que cette limite était située dans le fleuve, que ce soit sur le thalweg
ou sur la ligne médiane. Elle note à cet égard que la formulation employée

dans les arrêtés est la même que celle utilisée dans la lettre de 1901 et
qu’elle est tout aussi imprécise. La notion de «cours du fleuve» recouvre
plusieurs possibilités: une frontière sur l’une ou l’autre rive du fleuve ou
une frontière à un endroit quelconque dans le fleuve.
73. Même si, comme le soutient le Niger, une certaine pratique se

développa en partant de l’hypothèse que la limite se serait située à l’inté-
rieur du fleuve (voir paragraphe 83 ci-après), elle ne fut pas confirmée par
les arrêtés, bien que l’on puisse présumer que le gouverneur général

40 FRONTIER DISPUTE (JUDGMENT ) 126

1954 may have led to certain effectivités. Whether or not this is the case
will be considered in due course.

**

68. The Chamber will now turn to the acts invoked by Niger as evi-
dence of its legal title, namely the arrêtés issued by the Governor-General

of the AOF on 8 December 1934 and 27 October 1938 reorganizing the
internal administrative structure of the colony of Dahomey and contain-
ing a description of the boundaries of the various cercles. In both arrêtés
the north-west boundary of the cercle of Kandi is described as “the
course of the Niger as far as its confluence with the Mekrou”.

69. According to Niger these arrêtés are the formal and authoritative
confirmation that the boundary between Dahomey and the neighbouring
colony of Niger was located in the watercourse itself, as had already been
indicated in the letter of the Minister for the Colonies dated 7 September
1901. The arrêtés thus provide sufficient evidence of Niger’s title, even if

the title itself is not explicitly laid down in a prior regulative or adminis-
trative act.
70. Benin contends that these arrêtés were merely of an intra-colonial
character and were not intended to determine the boundary of Dahomey
with another colony. Benin further argues that the wording used is

imprecise and does not exclude a frontier on the left bank of the river.

*

71. The Chamber first notes that both arrêtés were issued by the
Governor-General, who was the authority competent to establish, delimit
and reorganize the cercles of colonies. In so far as they describe the boun-
daries of these cercles with the neighbouring colonies which also came
under his authority, the arrêtés do not have an exclusive internal charac-

ter but may also be relied upon in intercolonial relations. Consequently it
can be concluded on the basis of these arrêtés that the course of the River
Niger constituted the intercolonial boundary.
72. The Chamber is unable, however, to deduce therefrom that that
boundary was situated in the river, whether at the thalweg or the median
line. The Chamber notes in this regard that the terminology used in the

arrêtés is identical to that of the 1901 letter and is just as imprecise. The
notion of the “course of the river” covers a range of possibilities: a
boundary on either river bank or a boundary somewhere within the river.

73. Even if, as Niger contends, a certain practice had evolved on the

basis of a boundary within the river (see paragraph 83 below), that prac-
tice was not endorsed by the arrêtés, although it may be assumed that the
Governor-General would have been aware of the practice, which had

40127 DIFFÉREND FRONTALIER (ARRÊT )

n’était pas sans connaître une pratique existant depuis fort longtemps
déjà. De l’avis de la Chambre, il est évident que l’expression «le cours du

Niger» ne visait pas à préciser la localisation exacte de la limite, mais
simplement à indiquer la ligne de séparation entre les deux colonies.
74. La Chambre conclut dès lors que les arrêtés de 1934 et 1938 n’éta-
blissent pas une limite dans le fleuve; elle ne peut donc retenir la préten-
tion du Niger quant au titre qu’il revendique.

**

75. Compte tenu de ce qui précède, la Chambre conclut qu’aucune des
Parties n’a apporté la preuve de l’existence, durant la période coloniale,

d’un titre issu d’actes réglementaires ou administratifs.
76. La Chambre se penchera donc à présent sur la question de savoir
si les éléments de preuve fournis par les Parties s’agissant des effectivités
permettent de déterminer le tracé de la frontière dans le secteur du fleuve
Niger et d’indiquer auquel des deux Etats appartient chacune des îles du
fleuve, en particulier l’île de Lété.

77. La Chambre rappelle à cet égard que la Cour s’est déjà prononcée,
dans un certain nombre d’affaires, sur le rapport juridique entre effecti-
vités et titre.
Le passage le plus pertinent aux fins de la présente espèce figure dans
l’arrêt rendu en l’affaire du Différend frontalier (Burkina Faso/Répu-

blique du Mali), dans lequel la Chambre de la Cour, ayant dit que
«plusieurs éventualités d[evai]ent être distinguées», a notamment indi-
qué, lorsqu’elle a examiné le rapport juridique entre effectivités et titre,
que: «[d]ans l’éventualité où l’«effectivité» ne coexiste avec aucun
titre juridique, elle doit inévitablement être prise en considération»

(C.I.J. Recueil 1986, p. 587, par. 63; voir également Différend territorial
(Jamahiriya arabe libyenne/Tchad), arrêt, C.I.J. Recueil 1994 ,p .,
par. 75-76; Frontière terrestre et maritime entre le Cameroun et le Nigé-
ria (Cameroun c. Nigéria; Guinée équatoriale (intervenant)), arrêt,
C.I.J. Recueil 2002, p. 353, par. 68; Souveraineté sur Pulau Ligitan et

Pulau Sipadan (Indonésie/Malaisie), arrêt, C.I.J. Recueil 2002 , p. 678,
par. 126).

*
78. Les Parties font l’une et l’autre valoir que, pendant la période colo-

niale, des actes d’administration furent accomplis par leurs autorités
coloniales locales sur un certain nombre d’îles du fleuve. Elles évoquent,
à cet égard, l’octroi de permis de pacage, de pêche et d’abattage d’arbres,
ainsi que la perception de taxes, la surveillance sanitaire périodique du
cheptel, les patrouilles militaires et des activités de police.

79. S’agissant de l’administration du fleuve, le Niger soutient que,
pendant une période donnée, il a accompli des actes d’administration à
l’égard de l’ensemble de la partie pertinente du fleuve. Il affirme en

41 FRONTIER DISPUTE JUDGMENT ) 127

already been in existence for a considerable period of time. In the Cham-
ber’s view, it is evident that the term, “the course of the Niger”, was not

intended to indicate the precise location of the boundary but merely to
indicate the separation line between the two colonies.
74. The Chamber thus finds that the 1934 and 1938 arrêtés do not
establish a boundary in the river; it cannot therefore sustain Niger’s
claims as to title.

**

75. In view of the foregoing, the Chamber concludes that neither of
the Parties has succeeded in providing evidence of title on the basis of

regulative or administrative acts during the colonial period.
76. Therefore, the Chamber will now consider whether the evidence
furnished by the Parties with respect to effectivités can provide the basis
for it to determine the course of the frontier in the sector of the River
Niger and to which of the two States each of the islands in the river
belongs, in particular the island of Lété.

77. The Chamber recalls in this regard that the Court has previously
ruled in a number of cases on the legal relationship between effectivités
and title.
The passage most pertinent to the present case can be found in the
Judgment in the Frontier Dispute (Burkina Faso/Republic of Mali) case,

in which the Chamber of the Court, having noted that “a distinction
must be drawn among several eventualities” when evaluating the legal
relationship between effectivités and title, stated, inter alia, that: “[i]n the
event that the effectivité does not co-exist with any legal title, it must
invariably be taken into consideration” (I.C.J. Reports 1986, p. 587,

para. 63; see also Territorial Dispute (Libyan Arab Jamahiriya/Chad),
Judgment, I.C.J. Reports 1994, p. 38, paras. 75-76; Land and Maritime
Boundary between Cameroon and Nigeria (Cameroon v. Nigeria: Equa-
torial Guinea intervening), Judgment, I.C.J. Reports 2002 , p. 353,
para. 68; Sovereignty over Pulau Ligitan and Pulau Sipadan (Indonesia/

Malaysia), Judgment, I.C.J. Reports 2002 , p. 678, para. 126).

*
78. Both Parties claim that, during the colonial period, administrative

acts were carried out by their local colonial authorities on a number of
islands in the river. The Parties mention, in this regard, the provision of
licences for grazing, fishing and tree-felling, as well as the levying of
taxes, periodic sanitary control of livestock, military patrolling and police
activities.

79. With regard to the management of the river, Niger claims that, for
a certain period, it carried out management activities over the whole of
the relevant stretch of the river. Niger further maintains that, when this

41128 DIFFÉREND FRONTALIER (ARRÊT )

outre que, lorsque cette tâche a ensuite été confiée au Dahomey, ce der-
nier n’a pas administré l’ensemble du fleuve et que la colonie du Niger a

continué d’accomplir certains actes d’administration sur la partie du
fleuve qui touchait son territoire. De l’avis du Niger, ses activités conti-
nues excluent l’existence des droits allégués du Dahomey sur l’ensemble
du fleuve.
Le Bénin conteste que ces actes d’administration du fleuve puissent être

invoqués en tant qu’effectivités étant donné que, même si, à l’époque
coloniale, ces actes furent accomplis par les autorités d’une colonie don-
née, ils traduisaient l’exercice d’une fonction publique pour le compte de
l’AOF dans son ensemble.
80. Outre des éléments documentaires, le Bénin a produit, sous la

forme de «sommations interpellatives» (réponses à des demandes offi-
cielles), un certain nombre de témoignages. Pour le Niger, ces témoi-
gnages, recueillis plusieurs dizaines d’années après l’époque en question,
sont douteux et sujets à caution.
La Chambre note que le Bénin n’a pas invoqué lesdits témoignages au
cours des dernières phases de la procédure.

81. Enfin, les Parties ont toutes deux présenté plusieurs cartes à l’appui
de leur thèse. Toutefois, ni l’une ni l’autre ne soutient que ces cartes
revêtent la moindre «valeur juridique intrinsèque» en tant qu’elles cons-
titueraient l’«expression de la volonté de l’Etat ... concern[é]» (voir Diffé-
rend frontalier (Burkina Faso/République du Mali), C.I.J. Recueil 1986 ,

p. 582, par. 54; voir également paragraphe 44 ci-dessus). La Chambre
observe qu’aucune de ces cartes ne figurait en annexe à un texte officiel.

*

82. La Chambre examinera tout d’abord les diverses activités anté-
rieures à 1954 que les Parties présentent comme des effectivités.
83. Le 3 juillet 1914, le commandant du secteur de Gaya (Niger) et
administrateur adjoint, M. Sadoux, adressa au commandant du cercle du
Moyen-Niger (Dahomey) une lettre dans laquelle il se référait à l’utilisa-

tion de certaines îles par les habitants des deux rives du fleuve, lettre qu’il
avait rédigée «dans le but unique de déterminer nettement le cas dans
lequel des laissez-passer de pacage d[evai]ent être délivrés aux Peuhls des
deux rives et de délimiter la compétence territoriale des tribunaux indi-
gènes des deux colonies». Il avait annexé à cette lettre une liste d’îles
situées dans la zone frontalière, établie sur la base d’une reconnaissance

de l’ensemble du secteur du fleuve entre Koulou et la frontière nigériane
et indiquant à quelle colonie chacune des îles appartenait d’après son
emplacement par rapport au chenal navigable principal. Ce chenal était
défini par l’administrateur adjoint Sadoux comme étant le «grand bras
du fleuve, non le bras le plus large, mais le bras qui seul est navigable aux

basses eaux » (les italiques sont dans l’original).
84. Dans sa lettre, l’administrateur adjoint Sadoux invitait le comman-
dant du cercle du Moyen-Niger à venir le rencontrer à Gaya si la liste

42 FRONTIER DISPUTE JUDGMENT ) 128

task was subsequently entrusted to Dahomey, the latter did not manage
the whole of the river and that the colony of Niger continued to perform

certain management activities on the part of the river contiguous to it. In
Niger’s view, its continued activities negate Dahomey’s alleged rights on
the whole of the river.

Benin denies that such river management activities can be relied upon

as effectivités since, during the colonial period, such activities, even if
carried out by the authorities of individual colonies, were performed in
the exercise of a public function on behalf of the AOF as a whole.

80. Aside from documentary evidence, Benin has presented testimony

taken from certain individuals in the form of “sommations interpella-
tives” (replies to official enquiries). According to Niger, such testimony,
taken several decades after the period in question, is unreliable and
untrustworthy.
The Chamber notes that Benin did not invoke this testimony in the
later stages of the proceedings.

81. Finally, both Parties have presented a number of maps in order to
support their claims. Neither of them claims, however, that these maps
have any “intrinsic legal force” in the sense that they represent the
“physical expressions of the will of the State . . . concerned” (see Frontier
Dispute (Burkina Faso/Republic of Mali), I.C.J. Reports 1986 , p. 582,

para. 54; see also paragraph 44 above). The Chamber notes that none of
these maps were annexes to an official text.

*

82. The Chamber will first analyse the various activities prior to 1954,
presented as effectivités by the Parties.
83. On 3 July 1914 the commandant of the secteur of Gaya (Niger),
administrateur adjoint Sadoux, wrote a letter to the commandant of the
cercle of Moyen-Niger (Dahomey), in which he referred to the use of cer-

tain islands by the local inhabitants of both banks of the river. He wrote
this letter “for the sole purpose of clearly determining when grazing per-
mits [should] be issued to the Peuhls from both banks and delimiting the
territorial jurisdiction of the indigenous tribunals in the two colonies”.
Administrateur adjoint Sadoux attached to his letter a list of islands in the
border area, drawn up on the basis of an exploration of the whole stretch

of the river between Koulou and the Nigerian border, with an indication
of the colony to which each island belonged according to its position with
respect to the main navigable channel. Administrateur adjoint Sadoux
defined this channel as “the river’s main channel, not the widest channel,
but the only channel navigable at low water ” (emphasis in the original).

84. In his letter, administrateur adjoint Sadoux invited the comman-
dant of the cercle of Moyen-Niger to come to Gaya for further discus-

42129 DIFFÉREND FRONTALIER (ARRÊT )

devait donner lieu à des contestations. Le dossier de l’affaire ne révèle
aucune réaction à cette lettre. Il semble toutefois qu’une telle rencontre

ait eu lieu et débouché sur un arrangement.
Ainsi, dans un rapport intitulé «Monographie de Gaya» et daté de
mai 1917, M. Esperet, commandant par intérim de la subdivision de
Gaya, indiquait-il ceci:

«En juillet 1914 le commandant de subdivision de Gaya s’était
concerté sur place avec le commandant de cercle de Kandy, et ils
avaient [sou]mis des propositions à leurs chefs de colonie respectifs

tendant à ce que le bras toujours navigable du Niger fût uniquement
pris comme frontière. Quoique ces propositions n’aient reçu aucune
approbation officielle elles ont toujours depuis servi de bases au
règlement des contestations qui ont pu s’élever entre les différents
groupes peuhls.»

Il indiquait également que «le village de Lété» était administré depuis

Gaya.
85. Bien que des difficultés aient vu le jour en 1919 concernant l’admi-
nistration de l’île de Lété depuis Gaya, état de fait que le Dahomey
contestait, l’arrangement de 1914 — baptisé par la suite modus vivendi
de 1914 — semble avoir été respecté dans les années qui suivirent.
En 1925, le Dahomey suggéra d’échanger Lété contre les trois îles

situées en face de Gaya, qui lui avaient été attribuées dans la lettre de
M. Sadoux. Interrogé sur cette question par le gouverneur du Niger, le
commandant du cercle de Niamey (Niger) indiqua que la situation basée
sur le modus vivendi n’était pas pleinement satisfaisante. Aussi proposa-
t-il de

«prendre une limite plus nette ... [de telle manière que] la frontière

entre les deux colonies [soit] marquée par la rive droite du fleuve aux
plus hautes eaux [, afin que] toutes les îles appartiennent à la colonie
du Niger, sans contestation possible».

Il ne fut donné suite ni à la proposition du Dahomey, ni à celle du
commandant du cercle de Niamey.
86. Le dossier de l’affaire ne contient pas d’autres documents datant
de cette période et se rapportant à la question frontalière; le modus

vivendi de 1914 semble avoir donné satisfaction jusqu’aux événements
de 1954, qui furent à l’origine de l’échange de lettres décrit plus haut,
aux paragraphes 61 à 64. Le modus vivendi de 1914 est évoqué dans un
télégramme du 10 juin 1941 adressé au commandant du cercle de
Dosso (Niger) par le chef de la subdivision de Gaya, qui fait observer

que
«[l]e bras toujours navigable du Niger était uniquement pris comme

frontière. Les propositions n’ont jamais reçu aucune approbation
officielle depuis 1914. Il serait souhaitable qu’une décision inter-
vienne à ce sujet.» (Les italiques sont dans l’original.)

43 FRONTIER DISPUTE (JUDGMENT ) 129

sions if the contents of the list were contested. The case file does not
contain a reaction to the letter. However, it appears that such a meeting

did take place and led to an agreement.
Thus, in a report entitled “Monographie de Gaya” dated May 1917,
Mr. Esperet, who was heading ad interim the subdivision of Gaya, stated:

“In July 1914 the commandant of the subdivision of Gaya held
consultations on site with the commandant of the cercle of Kandy,
and they proposed to their respective heads of colony that the per-

manently navigable channel of the Niger solely be taken as the
boundary. Although those proposals were never officially approved,
they have since then always served as the basis for the settlement of
any disputes between different groups of Peuhls.”

He also mentioned that “the village of Lété” was administered by Gaya.

85. Although difficulties arose in 1919 with regard to the administra-
tion of the island of Lété by Gaya, which was contested by Dahomey, the
1914 arrangement, which became known as the 1914 modus vivendi,
seems to have been complied with in subsequent years.
In 1925 a proposal was made by Dahomey to exchange Lété for the

three islands opposite Gaya, which the Sadoux letter had attributed to
Dahomey. Asked for his reaction by the Governor of Niger, the comman-
dant of the cercle of Niamey (Niger) stated that the situation, based on
the modus vivendi, was not wholly satisfactory. He therefore suggested
that

“a clearer boundary be adopted: . . . the boundary between the two

colonies is marked by the right bank of the river at the line of highest
water. That will give all the islands to the colony of Niger without
any possibility of dispute.”

No action was taken upon either the proposal of Dahomey or that of
the commandant of the cercle of Niamey.
86. The case file does not contain other documents from that period
referring to the boundary issue; the 1914 modus vivendi seems to have

functioned satisfactorily until the events of 1954 which led to the corre-
spondence described in paragraphs 61 to 64 above. In a telegram of
10 June 1941 to the commandant of the cercle of Dosso (Niger), the chef
of the subdivision of Gaya referred to the 1914 modus vivendi. He com-
mented that:

“[t]he permanently navigable channel of the Niger was solely adopted

as boundary. Those proposals have never been officially approved
since 1914. A decision on the matter is desirable.” (Emphasis in the
original.)

43130 DIFFÉREND FRONTALIER (ARRÊT )

87. Pendant les années précédant 1954, l’île de Lété semble avoir été
administrée de manière ininterrompue par la subdivision de Gaya. Les

rôles d’impôts de Gaya — du moins ce qu’il en reste — font référence à
«Lété» pour les années 1925, 1927, 1928, 1930, 1932, 1935 et 1936.
«Lété» apparaît dans une liste de villages situés dans la subdivision de
Gaya, avec l’indication du nombre d’habitants pour les années 1932,
1945, 1946 et 1954. Elle figure également sur les listes issues des recense-

ments de 1944 et de 1945.
Enfin, en 1946, le gouverneur du Niger donna l’autorisation d’abattre
des palmiers sur l’île de Lété.
88. Le Bénin n’a pas produit de document officiel émanant d’autorités
coloniales et concernant un exercice effectif d’autorité, au cours de la

période considérée, sur l’île de Lété ou sur toute autre île située à gauche
du chenal navigable principal.

*
89. La Chambre abordera maintenant la question des effectivités pour

la période allant de 1954 à la date critique de 1960. Elle rappelle que,
dans une lettre datée du 27 août 1954, le gouverneur par intérim du Niger
écrivait que la frontière se situait à «la ligne des plus hautes eaux, côté
rive gauche du fleuve, à partir du village de Bandofay, jusqu’à la frontière
du Nigéria» et que «toutes les îles situées dans cette partie du fleuve f[ai-

saient] partie du territoire du Dahomey».
90. Pendant la période considérée, le Dahomey a de plus en plus sou-
vent prétendu détenir le droit d’administrer l’île de Lété.
Dans une lettre adressée le 23 mai 1955 au commandant du cercle de
Kandi, le chef de poste administratif de Malanville (Dahomey) men-

tionna l’apparition de certaines difficultés concernant la perception de
taxes auprès d’habitants du Niger possédant du bétail à Lété. Il demanda
«si l’agent percepteur du Dahomey [pouvait] opérer sur l’île de Lété».

Dans une lettre du 20 juin 1955 adressée au commandant du cercle de

Dosso (Niger) et concernant cette même question, le chef de la subdivi-
sion de Gaya, «sans vouloir soulever le moins du monde la question des
limites» (référence manifeste à la lettre du 27 août 1954), souligna que
l’île de Lété «[avait] constamment été tenue pour nigérienne».

91. En 1956, d’autres difficultés survinrent, concernant cette fois la

perception de taxes sur les exportations de poisson fumé à partir de Lété.
Le commandant du cercle de Kandi informa le gouverneur du Dahomey
de ces incidents et ajouta qu’il avait «retrouvé» la lettre du 27 août 1954,
dans laquelle il était indiqué que le fleuve ainsi que toutes les îles appar-
tenaient au Dahomey.

92. Cette même année, le directeur du service géographique de l’AOF
demanda aux commandants des cercles de Dosso et de Kandi de lui faire
connaître la nature et la date des textes officiels délimitant la frontière

44 FRONTIER DISPUTE (JUDGMENT ) 130

87. In the years prior to 1954, the island of Lété seems to have been
continuously administered by the subdivision of Gaya. The tax registers

of Gaya, in so far as they have been preserved, contain references to
“Lété” in the years 1925, 1927, 1928, 1930, 1932, 1935 and 1936.
“Lété” was included in a list of villages situated in the subdivision of
Gaya, with an indication of the number of inhabitants, in 1932, 1945,
1946 and 1954. It was also included in census lists in 1944 and 1945.

Finally, the Governor of Niger authorized the felling of palm trees on
the island of Lété in 1946.
88. Benin has not submitted any official document from colonial
authorities regarding an effective exercise of authority, during the period

under consideration, on the island of Lété or on any other island situated
to the left of the main navigable channel.

*
89. The Chamber will now turn to the effectivités in the period from

1954 until the critical date in 1960. It recalls that, on 27 August 1954, the
Governor ad interim of Niger wrote a letter in which he stated that the
boundary was situated “at the line of highest water, on the left bank of
the river, from the village of Bandofay to the frontier of Nigeria” and
that “all the islands situated in this part of the river [formed] part of the

territory of Dahomey”.
90. During this period, the claims of Dahomey to be entitled to admin-
ister the island of Lété became more frequent.
In a letter of 23 May 1955 to the commandant of the cercle of Kandi,
the chef de poste administratif at Malanville (Dahomey) mentioned cer-

tain difficulties which had arisen with respect to the collection of taxes
from inhabitants of Niger who held cattle on Lété. He raised the question
of “whether the tax collector of Dahomey [was] entitled to operate on the
island of Lété”.
In a letter of 20 June 1955 to the commandant of the cercle of Dosso

(Niger), dealing with the same incidents, the chef of the subdivision of
Gaya, “without in any way wishing to raise the question of the bound-
ary” (a clear reference to the letter of 27 August 1954), emphasized that
the island of Lété “[had] consistently been regarded as belonging to
Niger”.
91. In 1956, difficulties arose again, this time with regard to the collec-

tion of taxes on the export of smoked fish from Lété. The commandant of
the cercle of Kandi informed the Governor of Dahomey of these inci-
dents and added that he had “rediscovered” the letter of 27 August 1954
which stated that the river and all the islands belonged to Dahomey.

92. In that same year, the Director of the Geographical Service of the
AOF requested the commandants of the cercles of Dosso and Kandi to
inform him of the nature and date of the official texts that defined the

44131 DIFFÉREND FRONTALIER (ARRÊT )

entre le Dahomey et le Niger. A ce sujet, le chef de la subdivision de
Gaya fit savoir au commandant du cercle de Dosso qu’il avait «retrouvé»

la lettre de Sadoux de 1914, qu’il qualifia de «seul document sérieux sur
la question».
Le commandant du cercle de Kandi, dans une lettre datée du
28 juin 1956, informa le directeur du service géographique que «[c]ette
question de délimitation n’a[vait] fait à [s]a connaissance l’objet d’aucun

texte officiel». Il ajouta que des litiges avaient eu lieu par le passé et joi-
gnit à ce sujet la lettre du 27 août 1954 du gouverneur par intérim du
Niger.
93. «Lété» figurait sur la liste des bureaux de vote du Niger pour les
années 1955, 1957 et 1958.

94. De graves troubles advinrent en 1959, l’année précédant l’indépen-
dance. Dans une lettre du 16 juin 1959, le chef de la subdivision de
Malanville informa le premier ministre du Dahomey (alors république
autonome faisant partie de la Communauté française) de l’existence d’un
différend entre des habitants de Gouroubéri (Dahomey) et des Peuhls du
Niger, lesquels auraient occupé l’île de Lété en violation des droits de

propriété des Dahoméens. Il ajouta avoir consulté sans résultat son
homologue de Gaya, qui semblait soutenir les Peuhls et «ignor[ait] ... la
réglementation des îles». Le chef de la subdivision de Malanville fut
d’avis que la frontière se situait sur la rive gauche du fleuve et il indiqua
que, suivant les renseignements recueillis, l’île de Lété aurait toujours

appartenu aux habitants de Gouroubéri.
95. En décembre 1959, le commandant du cercle de Kandi se rendit à
Malanville. Le chef de la subdivision de Gaya fut invité à le rencontrer à
Lété, mais la rencontre n’eut pas lieu. Bien que le commandant du cercle
de Kandi se fut rendu sur l’île, le chef de la subdivision de Gaya «n’[était]

pas [allé] au rendez-vous». Il a été avancé par la suite qu’il n’était pas au
courant de cette visite.
96. Dans la nuit du 29 juin 1960, des émeutes se produisirent, au cours
desquelles quatre Peuhls du Niger furent tués et plusieurs habitations
brûlées. Dans une lettre datée du 3 juillet 1960, le commandant du cercle

de Kandi informa le ministre de l’intérieur du Dahomey que l’ordre avait
été rétabli et qu’une petite unité de police avait été installée sur l’île par
Gaya (Niger) et Malanville (Dahomey).
97. Le 13 juillet 1960, le président du conseil des ministres du Niger
(lequel était également une république autonome faisant à l’époque partie
de la Communauté française) proposa, dans une lettre adressée au pre-

mier ministre du Dahomey, de régler une fois pour toutes le différend par
un accord formel portant sur la question de «l’île de Lété (subdivision de
Gaya, Niger)».
Dans sa réponse datée du 29 juillet 1960, le premier ministre du Daho-
mey fit observer que cette question avait déjà été réglée par la lettre du

27 août 1954 mais qu’il ne s’opposait pas à ce que des consultations aient
lieu afin de parvenir à un accord formel.
Dans une lettre du 31 juillet 1960, le premier ministre du Niger insista

45 FRONTIER DISPUTE (JUDGMENT ) 131

boundary between Dahomey and Niger. In this regard, the chef of the
subdivision of Gaya informed the commandant of the cercle of Dosso that

he had “rediscovered” the 1914 Sadoux letter, which he called “the only
serious document on the matter”.
The commandant of the cercle of Kandi, by letter of 28 June 1956,
informed the Director of the Geographical Service that “this question of
boundaries [had], to [his] knowledge, never been dealt with in any official

text”. He added that there had been disputes in the past and attached in
this regard the letter of 27 August 1954 of the Governor ad interim of
Niger.
93. In 1955, 1957 and 1958, “Lété” is mentioned in the list of polling
stations in Niger.

94. Serious troubles arose in 1959, the year before independence. In a
letter of 16 June 1959 the chef of the subdivision of Malanville informed
the Prime Minister of Dahomey (which was at the time an autonomous
republic within the Communauté française) about a dispute between
inhabitants of Gouroubéri (Dahomey) and Peuhls from Niger who, in
violation of the property rights of the former, had occupied the island

of Lété. He added that he had had unsuccessful consultations with his
counterpart in Gaya, who seemed to support the Peuhls and “[was] . . .
unaware of the régime governing the islands”. The chef of the subdivision
of Malanville was of the view that the boundary was located on the left
bank of the river and stated that, according to his information, the island

of Lété had always belonged to the inhabitants of Gouroubéri.
95. In December 1959, the commandant of the cercle of Kandi visited
Malanville. The chef of the subdivision of Gaya was invited to meet him
on Lété but that meeting did not take place. Although the commandant
of the cercle of Kandi visited the island, the chef of the subdivision of

Gaya “did not come to the meeting”. It was said later on that he had
been unaware of the visit.
96. Riots broke out on the night of 29 June 1960, during which four
Peuhls from Niger were killed and a number of dwellings were set on fire.
In a letter dated 3 July 1960, the commandant of the cercle of Kandi

informed the Minister for the Interior of Dahomey that order had been
restored and that both Gaya (Niger) and Malanville (Dahomey) had
stationed a small police unit on the island.
97. In a letter dated 13 July 1960 to the Prime Minister of Dahomey,
the President of the Council of Ministers of Niger (which was also at the
time an autonomous republic within the Communauté française) pro-

posed to settle the dispute for once and for all through a formal agree-
ment on the question of the “island of Lété (subdivision of Gaya, Niger)”.

In his response dated 29 July 1960, the Prime Minister of Dahomey
observed that the matter had already been settled by the letter of

27 August 1954 but that he did not object to consultations in order to
reach a formal agreement.
In a letter dated 31 July 1960, the Prime Minister of Niger again

45132 DIFFÉREND FRONTALIER (ARRÊT )

encore une fois pour que la question soit définitivement réglée. Toutefois,

il ne fit pas référence à la lettre de 1954, mais, entre autres, à celle de 1914
et proposa de considérer comme frontière «la ligne médiane du bras per-
manent du fleuve, ou du bras le plus profond».

*

98. Sur la base des éléments de preuve produits devant elle, la
Chambre estime que, de 1914 à 1954, les termes du modus vivendi tels
que définis dans la lettre de Sadoux de 1914 furent dans l’ensemble
respectés et que, pendant cette période, le chenal navigable principal du

fleuve Niger fut considéré par les deux parties comme constituant la limite.
En conséquence, le Niger exerçait son autorité administrative sur les
îles situées à gauche et le Dahomey sur celles situées à droite de cette
ligne. Le droit du Niger à administrer l’île de Lété fut sporadiquement

remis en question pour des raisons d’ordre pratique, mais ne fut jamais
contesté ni en droit ni en fait.
99. S’agissant des îles situées en face de Gaya, la Chambre note que,
selon le modus vivendi établi par la lettre de Sadoux de 1914, ces îles
étaient considérées comme relevant du Dahomey. Elle rappelle à cet

égard que, en 1925, les autorités de cette dernière colonie avaient proposé
au Niger d’échanger les trois îles en face de Gaya contre l’île de Lété,
mais que cette proposition était demeurée sans suite (voir paragraphe 85
ci-dessus). Il n’a été soumis à la Chambre aucune information démon-
trant que, à l’époque, les îles en question étaient administrées par une

autorité autre que le cercle de Kandi (Dahomey). La Chambre en conclut
que, dans ce secteur du fleuve, la limite était alors regardée comme pas-
sant à gauche de ces trois îles.
100. La situation n’est pas aussi claire en ce qui concerne la période
allant de 1954 à 1960. Manifestement, les deux Parties ont occasionnel-

lement revendiqué des droits sur les îles, en particulier sur celle de Lété,
de même qu’elles ont parfois accompli des actes d’administration pour
manifester leur autorité. Toutefois, sur la base des éléments de preuve
soumis à la Chambre, celle-ci ne peut conclure que l’administration de
Lété — dont il ne fait aucun doute que, avant 1954, elle ait été exercée

par le Niger — ait à l’époque effectivement été transférée au Dahomey ou
reprise par celui-ci. A ce sujet, la Chambre relève que, selon un rapport
de la gendarmerie de Malanville du 1 erjuillet 1960, Lété était alors
«administrée par la subdivision de Gaya».

*

101. Le Bénin soutient que, à supposer que les autorités locales du
Niger aient effectivement administré Lété et d’autres îles pendant la
période allant de 1914 à 1954, elles n’auraient pu le faire avec la convic-

tion «d’agir de droit».
Selon le Bénin, le modus vivendi était simplement un accord temporaire

46 FRONTIER DISPUTE (JUDGMENT ) 132

pressed for a formal settlement. He referred, however, not to the 1954
letter but, inter alia, to the 1914 letter and proposed to take as the bound-

ary “the median line of the river’s permanent channel, or of its deepest
channel”.

*

98. On the basis of the evidence before it, the Chamber finds that,
from 1914 to 1954, the terms of the modus vivendi established by the 1914
Sadoux letter were in general respected and that, during this period, the
main navigable channel of the River Niger was considered by both sides
to be the boundary. As a result, administrative authority was exercised

by Niger on the islands to the left and by Dahomey on the islands to the
right of that line. The entitlement of Niger to administer the island of
Lété was sporadically called into question for practical reasons but was
neither legally nor factually contested.

99. With respect to the islands opposite Gaya, the Chamber notes

that, on the basis of the modus vivendi established by the 1914 Sadoux
letter, these islands were considered to fall under the jurisdiction of
Dahomey. It recalls in this regard that in 1925 a proposal was made to
Niger by the authorities of Dahomey for the exchange of the three islands
opposite Gaya for the island of Lété but that no action was taken on this

proposal (see paragraph 85 above). The Chamber has not received any
information to indicate that these islands were administered at that time
from anywhere else other than the cercle of Kandi (Dahomey). The
Chamber therefore concludes that, in this sector of the river, the bound-
ary was regarded as passing to the left of these three islands.

100. The situation is less clear in the period between 1954 and 1960. It
is apparent that both Parties periodically claimed rights over the islands,
in particular Lété, and also occasionally performed administrative acts as
a display of authority. However, on the basis of the evidence before it,
the Chamber cannot conclude that the administration of Lété, which

before 1954 was undoubtedly carried out by Niger, was effectively trans-
ferred to or taken over by Dahomey. In this respect, the Chamber notes
that a report of the gendarmerie of Malanville of 1 July 1960 stated that
Lété was “currently administered by the subdivision of Gaya”.

*

101. Benin contends that, even if the local authorities in Niger did
administer Lété and other islands during the period between 1914 and

1954, they could not have done so in the belief that they were acting “as
of right”.
In Benin’s view, the modus vivendi was merely a temporary and prac-

46133 DIFFÉREND FRONTALIER (ARRÊT )

et pratique dans l’attente d’un règlement définitif de la question fronta-

lière. De par sa nature même, il excluait l’existence de toute intention
d’agir de droit et ces actes administratifs ne sauraient donc être invoqués
à titre d’effectivités.
Concernant la période postérieure à 1954, le Bénin soutient que le
Niger, par la lettre du 27 août 1954, avait renoncé à toute intention

«d’agir de droit».
102. La Chambre observe que le concept d’intention et de volonté
d’agir à titre de souverain, tel que mentionné dans l’affaire du Statut juri-
dique du Groënland oriental (Danemark c. Norvège) (1933, C.P.J.I.
série A/B n 53, p. 45-46), est un concept de droit international qui ne

peut être transposé purement et simplement en droit colonial. En appli-
quant le principe de l’uti possidetis juris, la Chambre n’a d’autre tâche
que de rechercher si l’autorité sur les territoires que les Parties reven-
diquent aujourd’hui en tant qu’Etats souverains était effectivement

exercée par la colonie du Dahomey ou celle du Niger.

*

103. Par ces motifs et étant donné les circonstances de l’espèce, en par-

ticulier au vu des éléments de preuve fournis par les Parties, la Chambre
conclut que la frontière entre le Bénin et le Niger suit le chenal navigable
principal du fleuve Niger tel qu’il existait à la date des indépendances,
étant entendu que, au niveau des trois îles situées en face de Gaya, la
frontière passe à gauche desdites îles. Il en résulte que le Bénin a un titre

sur les îles situées entre la frontière ainsi définie et la rive droite du fleuve
et le Niger sur les îles situées entre cette frontière et la rive gauche du
fleuve.

**

104. La Chambre déterminera à présent l’emplacement précis de la
ligne frontière dans le chenal navigable principal, c’est-à-dire la ligne des
sondages les plus profonds telle qu’elle existait à la date des indépen-
dances; elle déterminera ensuite à laquelle des Parties chacune des îles

du fleuve appartient.
105. Le Bénin soutient que le chenal navigable du fleuve Niger est ins-
table et qu’il s’est modifié au fil des ans par suite d’un phénomène d’ensa-
blement du fleuve et de l’émergence de bancs de sable présentant un
caractère quasi permanent. Il a fait état du cas de plusieurs îles dont la

position par rapport au chenal navigable principal se serait modifiée sous
l’effet de ce phénomène, se référant en particulier aux îles de Kot-
cha Barou, Gagno Goungou et Dolé Barou.
106. Le Niger ne conteste pas que des phénomènes périodiques d’ensa-
blement puissent conduire à la formation de bancs de sable, mais soutient

que, en temps normal, ces accumulations de sable sont emportées par le
fleuve lors de la période de hautes eaux, pendant laquelle le cours de

47 FRONTIER DISPUTE (JUDGMENT ) 133

tical arrangement, pending a definitive settlement of the boundary issue.
By its very nature, it precluded the existence of an intention to act “as of

right” and these administrative acts cannot therefore be relied on as
effectivités.
As regards the period after 1954, Benin contends that Niger had, in the
letter of 27 August 1954, relinquished any intention to act “as of right”.

102. The Chamber observes that the concept of the intention and will
to act as sovereign, as mentioned in the Legal Status of Eastern Green-
land (Denmark v. Norway) case (1933, P.C.I.J., Series A/B, No. 53 ,
pp. 45-46), is a concept of international law and cannot be transplanted
purely and simply to colonial law. The Chamber’s sole task in applying

the principle of uti possidetis juris is to ascertain whether it was the
colony of Dahomey or that of Niger which effectively exercised authority
over the areas which the Parties now claim as sovereign States.

*

103. For all these reasons and in the circumstances of the case, par-
ticularly in light of the evidence furnished by the Parties, the Chamber
concludes that the boundary between Benin and Niger follows the main
navigable channel of the River Niger as it existed at the dates of inde-

pendence, it being understood that, in the vicinity of the three islands
opposite Gaya, the boundary passes to the left of these islands. Conse-
quently, Benin has title to the islands situated between the boundary thus
defined and the right bank of the river and Niger has title to the islands
between that boundary and the left bank of the river.

**

104. The Chamber will now proceed to determine the precise location
of the boundary line in the main navigable channel, namely the line of

deepest soundings, as it existed at the dates of independence; it will then
determine to which of the Parties each of the islands in the river belongs.

105. Benin contends that the navigable channel of the River Niger
is unstable and has changed over the years as the result of the siltation
of the river and the formation of sandbanks of a virtually permanent

character. Benin has highlighted a number of cases in which this pheno-
menon has allegedly resulted in a change in the position of the main
navigable channel around the islands. It referred, in particular, to the
islands of Kotcha Barou, Gagno Goungou and Dolé Barou.
106. Niger does not deny the periodic occurrence of siltation which

may lead to the formation of sandbanks but contends that, under normal
circumstances, these accumulations of sand are washed away during the
high-water season when the speed and pressure of the watermass increase

47134 DIFFÉREND FRONTALIER (ARRÊT )

celui-ci acquiert une vitesse et une force considérables. Il reconnaît que,
concernant l’île de Dolé Barou, le chenal principal s’est, depuis l’acces-

sion des deux Etats à l’indépendance, déplacé du côté gauche de l’île,
mais affirme que ce phénomène est probablement dû à des travaux
d’endiguement effectués en amont sur la rive gauche du fleuve. Le Niger
soutient en outre que plusieurs études hydrologiques, menées pendant
plus de soixante ans, ont démontré que le lit du fleuve était remarquable-

ment stable et que le chenal navigable principal n’avait pas changé de
position.
107. La Chambre commencera par observer que plusieurs levés hydro-
graphiques et topographiques ont été effectués au fil des ans. A cet égard,
les documents les plus pertinents sont les suivants:

1. les cartes réalisées à l’issue de la mission du lieutenant Hourst en
1896;
2. le rapport de la mission effectuée par l’ingénieur A. M. J. Beneyton
entre 1926 et 1932 pour le compte de l’AOF;
3. le rapport final issu d’une étude sur la navigabilité du Moyen-Niger

réalisée entre 1967 et 1970 par l’entreprise Netherlands Engineering
Consultants (NEDECO) sur demande des Gouvernements du Daho-
mey, du Mali, du Niger et de la Fédération du Nigéria;
4. une série de photographies aériennes annotées prises en 1975 et
publiées dans un rapport de l’IGN-Paris en 1979.

108. La Chambre note que la position du chenal navigable principal,
telle qu’établie par ces diverses missions, apparaît plutôt constante, ce
qui tendrait à indiquer que le lit du fleuve est relativement stable et que
les ensablements ayant pu se produire ont rarement donné lieu à des

changements notables de l’emplacement du chenal navigable principal.
Tel semble avoir été le cas tant à l’époque coloniale qu’après l’indépen-
dance.
109. Etant donné que la Chambre est appelée à déterminer le tracé de
la limite au moment des indépendances, le rapport produit en 1970 par

NEDECO constitue la source de renseignements la plus utile sur la situa-
tion existant à la date critique. La stabilité du fleuve étant démontrée, il
est permis de supposer que la situation entre 1967 et 1970 était quasiment
identique à celle de 1960.
110. A ce sujet, la Chambre attache une grande importance au fait que
l’étude de 1967-1970 a été conduite par une entreprise indépendante répu-

tée pour ses compétences et son expérience et que ses résultats figurent
dans un rapport qui a été présenté aux gouvernements de quatre Etats
riverains, dont les Parties à la présente affaire. En outre, les conclusions
énoncées dans le rapport de NEDECO n’ont pas été contestées à
l’époque de leur publication et sont corroborées par des études tant

antérieures qu’ultérieures.
111. Le rapport de NEDECO étudie la navigabilité du fleuve Niger
entre Tossaye au Mali et Yelwa au Nigéria. Il couvre donc toute la partie

48 FRONTIER DISPUTE (JUDGMENT ) 134

considerably. Niger admits that, with respect to the island of Dolé Barou,
the main channel has moved to the left side of the island since the acces-

sion of the two States to independence, but submits that this may be due
to works on dykes carried out upstream on the left bank of the river. It
further submits that a number of hydrological surveys, carried out over a
period of more than 60 years, have demonstrated that the riverbed is
remarkably stable and that the main navigable channel has remained

unchanged.

107. The Chamber initially notes that, over the course of time, a
number of hydrographic and topographic surveys have taken place. In
this respect, the following studies are the most pertinent:

1. the maps produced as a result of the mission of Lieutenant Hourst in
1896;
2. the report of the mission carried out by the engineer A. M. J. Beney-
ton between 1926 and 1932 on behalf of the AOF;
3. the final report of a study on the navigability of the Middle Niger,

carried out by the Netherlands Engineering Consultants (NEDECO)
between 1967 and 1970 at the request of the Governments of Daho-
mey, Mali, Niger and the Federation of Nigeria;
4. a series of annotated aerial photographs taken in 1975 and published
in a report of IGN-Paris in 1979.

108. The Chamber observes that the position of the main navigable
channel as determined by each of the missions is very similar. The
Chamber considers that this indicates that the riverbed is relatively
stable and that any siltation which has taken place has rarely led to a

noticeable change in the location of the main navigable channel. This
appears to have been the case in both the colonial and post-independence
period.
109. Given that the Chamber has to determine the course of the
boundary at the time of independence, the NEDECO report of 1970 pro-

vides the most useful information on the situation at the critical date. In
view of the proven stability of the riverbed, it may be assumed that the
situation between 1967 and 1970 was virtually identical with that in 1960.

110. In this respect, the Chamber considers it of great importance that
the 1967-1970 survey was carried out by an independent firm renowned

for its expertise and experience and that the results were contained in a
report presented to the Governments of four riparian States, including
the Parties to the present case. Furthermore, the findings of the NEDECO
study were not contested at the time of their publication and they are
corroborated by both earlier and later studies.

111. The report of the NEDECO study examines the navigability of
the River Niger between Tossaye in Mali and Yelwa in Nigeria. It there-

48135 DIFFÉREND FRONTALIER (ARRÊT )

du fleuve qui se situe entre le Bénin et le Niger, de son point de confluence

avec la Mékrou jusqu’à la frontière nigériane.
112. Les cartes qui figurent en annexe au rapport sont très détaillées,
chacune d’elles couvrant un secteur de 25 kilomètres et présentant le pro-
fil longitudinal du chenal navigable principal, sur la base des relevés issus
de sondages échographiques qui ont été effectués à diverses reprises, tant

en période de hautes eaux qu’en période de basses eaux, au moyen d’un
écho-sondeur embarqué. Aux fins de contrôler l’emplacement du chenal,
NEDECO a réalisé des sections transversales et a fixé le point le plus pro-
fond de chaque section. Ensuite, la distance de ce point jusqu’aux deux
rives ou, dans certains cas, jusqu’à l’une de celles-ci, a été mesurée. Ces

distances ont enfin été reportées sur une carte topographique à l’échelle
de 1/50000.
La Chambre constate que, d’une manière générale, le chenal navigable
principal tel qu’il ressort du rapport de NEDECO coïncide ou présente

de grandes similitudes avec celui qui est décrit sur les cartes et croquis
établis à l’issue des missions Hourst de 1896 et Beneoton de 1926-1932.
113. La Chambre relève en outre que la carte n 36 du rapport établi
par NEDECO indique que, dans le secteur faisant face au village de
Gaya, le fleuve compte deux chenaux navigables. Sur la base des infor-

mations disponibles, il n’est pas possible de dire lequel est en permanence
le plus profond. Cela est toutefois sans importance dans le cas présent,
compte tenu des conclusions que la Chambre a déjà tirées, aux para-
graphes 99 et 103 ci-dessus, des effectivités coloniales dans ce secteur.
La Chambre estime que, dans le secteur des trois îles situées face à Gaya,

la frontière est constituée par la ligne des sondages les plus profonds du
chenal navigable gauche. Cependant, au niveau de la dernière de ces
îles, Kata Goungou, la frontière doit s’écarter de cette ligne et passer à
gauche de l’île.
114. En dehors de l’exception indiquée au paragraphe précédent, la

frontière entre les Parties suit donc la ligne des sondages les plus profonds
du chenal navigable principal du fleuve Niger telle qu’elle résulte du rap-
port de NEDECO de 1970, à partir de l’intersection de cette ligne avec la
ligne médiane de la Mékrou jusqu’à son intersection avec la frontière des
Parties avec le Nigéria.

Face à Gaya, la frontière est constituée par la ligne des sondages les
plus profonds du chenal navigable gauche, à partir du point de coordon-
nées 11°52′29″ de latitude nord et 3°25′34″ de longitude est jusqu’au
point de coordonnées 11°51′55″ de latitude nord et 3°27′41″ de longi-
tude est, où la frontière s’écarte de ce chenal et passe à gauche de l’île de

Kata Goungou, pour rejoindre ensuite le chenal navigable principal au
point de coordonnées 11°51′41″ de latitude nord et 3°28′53″ de longi-
tude est.
115. Il découle de ce qui précède que la ligne frontière entre le Bénin et
le Niger dans le secteur du fleuve Niger passe, d’amont en aval, par les

points, numérotés de 1 à 154, dont les coordonnées sont indiquées dans la
table ci-après:

49 FRONTIER DISPUTE (JUDGMENT ) 135

fore covers the whole stretch of the river between Benin and Niger from
its confluence with the Mekrou to the frontier with Nigeria.

112. The maps annexed to the report are very detailed, each of them
covering a stretch of 25 km and showing the longitudinal profile of the
main navigable channel based on the results of echosounding carried out,
using a boat-mounted echo-sounder, on various occasions during the
high and low water season. In order to check the position of the channel,

cross-sections were made by NEDECO and the deepest point of each sec-
tion was fixed. Subsequently, the distance was measured from this point
to the two banks, or in certain cases to one of them. Finally, these dis-
tances were represented on a topographical map on a scale of 1:50,000.

The Chamber observes that the main navigable channel identified by
the report of the NEDECO study generally coincides with or is very simi-
lar to the one that is represented in the maps and sketch-maps resulting
from the 1896 Hourst mission and the 1926-1932 Beneyton mission.
113. The Chamber further notes that map No. 36 of the NEDECO

report indicates that in the sector opposite the village of Gaya, the river
has two navigable channels. On the basis of the available data, it is not
possible to say which one is consistently deeper. This is however without
consequence in the present case given the conclusions drawn by the
Chamber, in paragraphs 99 and 103 above, from the colonial effectivités

in that sector. The Chamber considers that, in the sector of the three
islands opposite Gaya, the boundary is constituted by the line of deepest
soundings of the left navigable channel. However, in the vicinity of the
last of these islands, Kata Goungou, the boundary deviates from that line
and passes to the left of that island.

114. With the exception indicated in the previous paragraph, the
boundary between the Parties therefore follows the line of deepest sound-
ings of the main navigable channel of the River Niger as it appears in the
1970 NEDECO report, from the intersection of this line with the median

line of the River Mekrou until its intersection with the boundary of the
Parties with Nigeria.
Opposite Gaya, the boundary is constituted by the line of deepest
soundings of the left navigable channel from the point situated at co-
ordinates 11°52′29″ latitude North and 3°25′34″ longitude East until
the point located at co-ordinates 11°51′55″ latitude North and 3°27′41″

longitude East, where the boundary deviates from this channel and passes
to the left of the island of Kata Goungou, subsequently rejoining the
main navigable channel at the point located at co-ordinates 11°51′41″
latitude North and 3°28′53″ longitude East.
115. It follows from the foregoing that the boundary line between

Benin and Niger in the sector of the River Niger, proceeding down-
stream, passes through the points numbered from 1 to 154, the co-ordi-
nates of which are indicated in the table below:

49136 DIFFÉREND FRONTALIER (ARRÊT)

(Ellipsoïde de Clarke 1880)

Coordonnées sur la ligne
Point n° Latitude nord Longitude est

001 12°24′31″ 2°49′36″
002 12°24′25″ 2°50′08″
003 12°24′24″ 2°50′20″
004 12°24′06″ 2°50′43″
005 12°23′54″ 2°50′55″

006 12°23′46″ 2°51′05″
007 12°23′34″ 2°51′25″
008 12°23′32″ 2°51′45″
009 12°23′25″ 2°52′07″
010 12°23′16″ 2°52′21″

011 12°22′56″ 2°52′40″
012 12°22′41″ 2°52′52″
013 12°22′38″ 2°53′04″
014 12°22′00″ 2°53′18″
015 12°21′38″ 2°53′33″
016 12°21′11″ 2°54′04″

017 12°21′07″ 2°54′16″
018 12°20′58″ 2°54′25″
019 12°20′36″ 2°54′52″
020 12°20′12″ 2°55′19″
021 12°20′09″ 2°55′25″
022 12°20′06″ 2°55′38″

023 12°19′41″ 2°56′01″
024 12°19′29″ 2°56′08″
025 12°19′06″ 2°56′29″
026 12°19′00″ 2°56′40″
027 12°18′14″ 2°57′11″

028 12°17′55″ 2°57′16″
029 12°17′15″ 2°57′47″
030 12°17′03″ 2°58′10″
031 12°16′52″ 2°58′41″
032 12°16′38″ 2°59′32″
033 12°16′10″ 3°00′35″

034 12°15′59″ 3°00′49″
035 12°15′26″ 3°01′10″
036 12°15′01″ 3°01′18″
037 12°14′27″ 3°01′31″
038 12°14′01″ 3°01′47″

039 12°13′43″ 3°02′04″
040 12°13′41″ 3°02′11″
041 12°13′34″ 3°02′24″
042 12°13′12″ 3°02′45″
043 12°12′31″ 3°03′33″

50 FRONTIER DISPUTE (JUDGMENT ) 136

(Clarke 1880 Ellipsoid)

Co-ordinates on the line
Point No. Latitude North Longitude East

001 12°24′31″ 2°49′36″
002 12°24′25″ 2°50′08″
003 12°24′24″ 2°50′20″
004 12°24′06″ 2°50′43″
005 12°23′54″ 2°50′55″

006 12°23′46″ 2°51′05″
007 12°23′34″ 2°51′25″
008 12°23′32″ 2°51′45″
009 12°23′25″ 2°52′07″
010 12°23′16″ 2°52′21″

011 12°22′56″ 2°52′40″
012 12°22′41″ 2°52′52″
013 12°22′38″ 2°53′04″
014 12°22′00″ 2°53′18″
015 12°21′38″ 2°53′33″
016 12°21′11″ 2°54′04″

017 12°21′07″ 2°54′16″
018 12°20′58″ 2°54′25″
019 12°20′36″ 2°54′52″
020 12°20′12″ 2°55′19″
021 12°20′09″ 2°55′25″
022 12°20′06″ 2°55′38″

023 12°19′41″ 2°56′01″
024 12°19′29″ 2°56′08″
025 12°19′06″ 2°56′29″
026 12°19′00″ 2°56′40″
027 12°18′14″ 2°57′11″

028 12°17′55″ 2°57′16″
029 12°17′15″ 2°57′47″
030 12°17′03″ 2°58′10″
031 12°16′52″ 2°58′41″
032 12°16′38″ 2°59′32″
033 12°16′10″ 3°00′35″

034 12°15′59″ 3°00′49″
035 12°15′26″ 3°01′10″
036 12°15′01″ 3°01′18″
037 12°14′27″ 3°01′31″
038 12°14′01″ 3°01′47″

039 12°13′43″ 3°02′04″
040 12°13′41″ 3°02′11″
041 12°13′34″ 3°02′24″
042 12°13′12″ 3°02′45″
043 12°12′31″ 3°03′33″

50137 DIFFÉREND FRONTALIER (ARRÊT)

Coordonnées sur la ligne

Point n° Latitude nord Longitude est

044 12°12′22″ 3°03′36″
045 12°12′06″ 3°03′29″
046 12°11′46″ 3°03′35″
047 12°11′01″ 3°04′19″
048 12°10′36″ 3°04′56″
049 12°10′26″ 3°05′49″

050 12°10′21″ 3°06′03″
051 12°10′05″ 3°06′25″
052 12°09′46″ 3°06′50″
053 12°09′27″ 3°07′30″
054 12°09′16″ 3°07′40″

055 12°08′52″ 3°07′39″
056 12°08′25″ 3°07′38″
057 12°08′10″ 3°07′59″
058 12°07′48″ 3°08′41″
059 12°07′21″ 3°09′15″
060 12°06′49″ 3°10′07″

061 12°06′21″ 3°10′35″
062 12°05′43″ 3°10′58″
063 12°05′24″ 3°11′07″
064 12°05′01″ 3°11′20″
065 12°04′44″ 3°11′39″
066 12°04′33″ 3°11′54″

067 12°04′24″ 3°12′04″
068 12°04′09″ 3°12′22″
069 12°03′58″ 3°12′43″
070 12°03′39″ 3°13′13″
071 12°03′20″ 3°13′29″

072 12°03′01″ 3°13′49″
073 12°02′51″ 3°13′57″
074 12°02′18″ 3°14′05″
075 12°01′57″ 3°14′22″
076 12°01′53″ 3°14′36″
077 12°01′54″ 3°15′06″

078 12°01′30″ 3°15′33″
079 12°01′10″ 3°15′39″
080 12°00′53″ 3°16′13″
081 12°00′42″ 3°16′13″
082 12°00′21″ 3°15′54″

083 12°00′09″ 3°15′38″
084 11°59′52″ 3°15′25″
085 11°59′24″ 3°15′34″
086 11°58′54″ 3°16′08″
087 11°58′33″ 3°16′21″

51 FRONTIER DISPUTE (JUDGMENT ) 137

Co-ordinates on the line

Point No. Latitude North Longitude East

044 12°12′22″ 3°03′36″
045 12°12′06″ 3°03′29″
046 12°11′46″ 3°03′35″
047 12°11′01″ 3°04′19″
048 12°10′36″ 3°04′56″
049 12°10′26″ 3°05′49″

050 12°10′21″ 3°06′03″
051 12°10′05″ 3°06′25″
052 12°09′46″ 3°06′50″
053 12°09′27″ 3°07′30″
054 12°09′16″ 3°07′40″

055 12°08′52″ 3°07′39″
056 12°08′25″ 3°07′38″
057 12°08′10″ 3°07′59″
058 12°07′48″ 3°08′41″
059 12°07′21″ 3°09′15″
060 12°06′49″ 3°10′07″

061 12°06′21″ 3°10′35″
062 12°05′43″ 3°10′58″
063 12°05′24″ 3°11′07″
064 12°05′01″ 3°11′20″
065 12°04′44″ 3°11′39″
066 12°04′33″ 3°11′54″

067 12°04′24″ 3°12′04″
068 12°04′09″ 3°12′22″
069 12°03′58″ 3°12′43″
070 12°03′39″ 3°13′13″
071 12°03′20″ 3°13′29″

072 12°03′01″ 3°13′49″
073 12°02′51″ 3°13′57″
074 12°02′18″ 3°14′05″
075 12°01′57″ 3°14′22″
076 12°01′53″ 3°14′36″
077 12°01′54″ 3°15′06″

078 12°01′30″ 3°15′33″
079 12°01′10″ 3°15′39″
080 12°00′53″ 3°16′13″
081 12°00′42″ 3°16′13″
082 12°00′21″ 3°15′54″

083 12°00′09″ 3°15′38″
084 11°59′52″ 3°15′25″
085 11°59′24″ 3°15′34″
086 11°58′54″ 3°16′08″
087 11°58′33″ 3°16′21″

51138 DIFFÉREND FRONTALIER (ARRÊT)

Coordonnées sur la ligne

Point n° Latitude nord Longitude est

088 11°58′14″ 3°16′30″
089 11°57′56″ 3°16′42″
090 11°57′19″ 3°16′51″
091 11°56′40″ 3°16′45″
092 11°56′07″ 3°17′00″
093 11°56′01″ 3°17′47″

094 11°55′55″ 3°17′56″
095 11°55′48″ 3°18′00″
096 11°55′01″ 3°18′13″
097 11°54′51″ 3°18′13″
098 11°54′42″ 3°18′12″

099 11°54′12″ 3°18′15″
100 11°53′20″ 3°18′50″
101 11°53′08″ 3°19′06″
102 11°52′54″ 3°19′17″
103 11°52′53″ 3°19′43″
104 11°53′11″ 3°20′15″

105 11°53′09″ 3°20′23″
106 11°52′57″ 3°20′43″
107 11°53′08″ 3°21′38″
108 11°53′13″ 3°22′13″
109 11°53′13″ 3°22′37″
110 11°53′11″ 3°23′01″

111 11°52′59″ 3°23′37″
112 11°52′39″ 3°24′11″
113 11°52′37″ 3°24′44″
114 11°52′43″ 3°25′06″
115 11°52′29″ 3°25′34″

116 11°52′30″ 3°25′55″
117 11°52′37″ 3°26′28″
118 11°52′30″ 3°26′50″
119 11°51′55″ 3°27′41″
120 11°51′53″ 3°28′20″
121 11°51′41″ 3°28′53″

122 11°51′25″ 3°29′12″
123 11°51′03″ 3°29′22″
124 11°50′36″ 3°29′38″
125 11°50′03″ 3°30′11″
126 11°49′39″ 3°30′34″

127 11°49′22″ 3°30′53″
128 11°48′53″ 3°31′16″
129 11°48′29″ 3°31′15″
130 11°48′01″ 3°31′10″
131 11°47′34″ 3°31′13″

52 FRONTIER DISPUTE (JUDGMENT ) 138

Co-ordinates on the line

Point No. Latitude North Longitude East

088 11°58′14″ 3°16′30″
089 11°57′56″ 3°16′42″
090 11°57′19″ 3°16′51″
091 11°56′40″ 3°16′45″
092 11°56′07″ 3°17′00″
093 11°56′01″ 3°17′47″

094 11°55′55″ 3°17′56″
095 11°55′48″ 3°18′00″
096 11°55′01″ 3°18′13″
097 11°54′51″ 3°18′13″
098 11°54′42″ 3°18′12″

099 11°54′12″ 3°18′15″
100 11°53′20″ 3°18′50″
101 11°53′08″ 3°19′06″
102 11°52′54″ 3°19′17″
103 11°52′53″ 3°19′43″
104 11°53′11″ 3°20′15″

105 11°53′09″ 3°20′23″
106 11°52′57″ 3°20′43″
107 11°53′08″ 3°21′38″
108 11°53′13″ 3°22′13″
109 11°53′13″ 3°22′37″
110 11°53′11″ 3°23′01″

111 11°52′59″ 3°23′37″
112 11°52′39″ 3°24′11″
113 11°52′37″ 3°24′44″
114 11°52′43″ 3°25′06″
115 11°52′29″ 3°25′34″

116 11°52′30″ 3°25′55″
117 11°52′37″ 3°26′28″
118 11°52′30″ 3°26′50″
119 11°51′55″ 3°27′41″
120 11°51′53″ 3°28′20″
121 11°51′41″ 3°28′53″

122 11°51′25″ 3°29′12″
123 11°51′03″ 3°29′22″
124 11°50′36″ 3°29′38″
125 11°50′03″ 3°30′11″
126 11°49′39″ 3°30′34″

127 11°49′22″ 3°30′53″
128 11°48′53″ 3°31′16″
129 11°48′29″ 3°31′15″
130 11°48′01″ 3°31′10″
131 11°47′34″ 3°31′13″

52139 DIFFÉREND FRONTALIER ARRÊT )

Coordonnées sur la ligne
Point n° Latitude nord Longitude est

132 11°47′16″ 3°31′22″
133 11°47′06″ 3°31′35″
134 11°46′56″ 3°31′51″
135 11°46′46″ 3°32′06″
136 11°46′41″ 3°32′31″

137 11°46′42″ 3°32′51″
138 11°46′46″ 3°33′13″
139 11°46′45″ 3°33′31″
140 11°46′33″ 3°33′46″

141 11°46′21″ 3°33′53″
142 11°46′09″ 3°33′56″
143 11°45′53″ 3°33′55″
144 11°45′35″ 3°33′45″
145 11°45′06″ 3°33′15″

146 11°44′32″ 3°33′02″
147 11°44′05″ 3°32′59″
148 11°43′27″ 3°33′23″
149 11°43′16″ 3°33′42″
150 11°43′08″ 3°34′07″

151 11°43′11″ 3°34′16″
152 11°42′58″ 3°34′38″
153 11°42′52″ 3°34′58″
154 11°42′39″ 3°35′18″

Les points constituant la ligne frontière figurent par ailleurs, à titre
purement illustratif, sur le croquis n 4 (en six feuilles) joint au présent
1
arrêt .

*

116. La Chambre déterminera à présent à laquelle des Parties appar-
tient chacune des îles du fleuve Niger, en suivant son cours d’amont en
aval, depuis son point de confluence avec la Mékrou jusqu’à la frontière

nigériane.
La Chambre n’a pas reçu d’informations sûres qui feraient état de la
formation ou de la disparition d’îles entre 1960 et 1967-1970. S’agissant
des années postérieures, elle observe qu’une des îles identifiées par le
Niger, à savoir Sandi Tounga Barou, qui n’apparaît sur aucune carte

antérieure à 1973, figure sur différentes photographies aériennes et
images SPOT à partir de cette année; dès lors, la Chambre aura à déter-
miner ci-après l’appartenance de cette île à l’une ou l’autre des Parties.

1
On trouvera un exemplaire de cette carte dans une pochette placée à la fin du présent
fascicule ou du volume C.I.J. Recueil 2005 selon le cas. [Note du Greffe.]

53 FRONTIER DISPUTE JUDGMENT ) 139

Co-ordinates on the line

Point No. Latitude North Longitude East
132 11°47′16″ 3°31′22″

133 11°47′06″ 3°31′35″
134 11°46′56″ 3°31′51″
135 11°46′46″ 3°32′06″
136 11°46′41″ 3°32′31″
137 11°46′42″ 3°32′51″

138 11°46′46″ 3°33′13″
139 11°46′45″ 3°33′31″
140 11°46′33″ 3°33′46″
141 11°46′21″ 3°33′53″
142 11°46′09″ 3°33′56″

143 11°45′53″ 3°33′55″
144 11°45′35″ 3°33′45″
145 11°45′06″ 3°33′15″
146 11°44′32″ 3°33′02″
147 11°44′05″ 3°32′59″

148 11°43′27″ 3°33′23″
149 11°43′16″ 3°33′42″
150 11°43′08″ 3°34′07″
151 11°43′11″ 3°34′16″
152 11°42′58″ 3°34′38″

153 11°42′52″ 3°34′58″
154 11°42′39″ 3°35′18″

The points that constitute the boundary line are further represented,
purely for illustrative purposes, on sketch-map No. 4 (in six sheets)
attached to the present Judgment .

*
116. The Chamber will now determine to which of the Parties each of

the islands in the River Niger belongs, following the course of the river
downstream from its confluence with the Mekrou to the frontier with
Nigeria.
The Chamber has not received reliable information that new islands
formed nor that islands disappeared between 1960 and 1967-1970. As

regards subsequent years, it observes that one of the islands identified by
Niger, namely Sandi Tounga Barou, which is not represented on any
map prepared before 1973, does appear on various aerial photographs
and SPOT images taken from 1973 onwards. The Chamber must conse-
quently determine to which of the Parties this island belongs. With

1A copy of this map will be found in a pocket at the end of this fascicle or inside the
back cover of the volume of I.C.J. Reports 2005. [Note by the Registry.]

53140 DIFFÉREND FRONTALIER (ARRÊT )

Quant à l’«île» de Pekinga, dont le Niger, dans ses conclusions finales,
prétend qu’elle appartient au Bénin, la Chambre note que celle-ci ne

peut être identifiée comme une île distincte sur les cartes annexées
au rapport NEDECO, mais qu’elle semble plutôt faire partie de la rive
du fleuve, du côté du Bénin.
117. La Chambre conclut des paragraphes 103 et suivants ci-dessus
que

1. Boumba Barou Béri appartient au Niger;
2. Boumba Barou Kaïna appartient au Niger;

3. Kouassi Barou appartient au Niger;
4. Sansan Goungou, également dénommée Fodofey (ou Fandofay)
Barou ou Koro Kouara Barou, appartient au Niger;
5. Lété Goungou appartient au Niger;
6. Tondi Kwaria Barou, également dénommée Faran Tounga Barou,

appartient au Bénin;
7. Monboye Tounga appartient au Niger;
8. Sini Goungou, également dénommée Tondika Goungou, appartient
au Niger;
9. Lama Barou appartient au Niger;
10. Kotcha Barou, également dénommée Bagou Barou, Gouandi Tounga

Barou ou Ibrahim Ba Ama Founbou, appartient au Niger;
11. Koki Barou appartient au Bénin;
12. Gagno Goungou, également dénommée Gaya Goungou ou Karsani
Goungou, appartient au Bénin;
13. Kata Goungou appartient au Bénin;

14. Sandi Tounga Barou appartient au Bénin;
15. Gandégabi Barou Kaïna appartient au Bénin;
16. Gandégabi Barou Béri appartient au Niger;
17. Guirawa Barou, également dénommée Issa Kaïna, appartient au
Niger;

18. Dan Koré Guirawa, également dénommée Bédari, appartient au
Bénin;
19. Barou Elhadji Dan Djoda, également dénommée Sabonbarou ou
Wéra Barou, appartient au Bénin;
20. Koundou Barou appartient au Bénin;

21. Elhadji Chaïbou Barou Béri appartient au Niger;
22. Elhadji Chaïbou Barou Kaïna appartient au Niger;
23. Goussou Barou, également dénommée Gattawani Béri Barou ou
Dandanikoye Barou, appartient au Niger;
24. Beyo Barou, également dénommée Wéra Kaïna Barou, appartient au
Niger;

25. Dolé Barou, également dénommée Barou Béri ou Bani Koubaye,
appartient au Niger.

Ces différentes îles sont figurées sur le croquis illustratif mentionné au
paragraphe 115 ci-dessus.
118. Enfin, la Chambre observe que la détermination de l’apparte-

54 FRONTIER DISPUTE (JUDGMENT ) 140

respect to the “island” of Pekinga, which Niger in its final submissions
attributed to Benin, the Chamber notes that it is not identifiable as a

separate island on the maps annexed to the NEDECO report, but instead
appears to be part of the river bank on the Benin side.

117. The Chamber finds, on the basis of paragraphs 103 et seq.,
that

1. Boumba Barou Béri belongs to Niger;
2. Boumba Barou Kaïna belongs to Niger;

3. Kouassi Barou belongs to Niger;
4. Sansan Goungou, also known as Fodofey (or Fandofay) Barou or
Koro Kouara Barou, belongs to Niger;
5. Lété Goungou belongs to Niger;
6. Tondi Kwaria Barou, also known as Faran Tounga Barou, belongs

to Benin;
7. Monboye Tounga belongs to Niger;
8. Sini Goungou, also known as Tondika Goungou, belongs to Niger;

9. Lama Barou belongs to Niger;
10. Kotcha Barou, also known as Bagou Barou, Gouandi Tounga Barou

or Ibrahim Ba Ama Founbou, belongs to Niger;
11. Koki Barou belongs to Benin;
12. Gagno Goungou, also known as Gaya Goungou or Karsani
Goungou, belongs to Benin;
13. Kata Goungou belongs to Benin;

14. Sandi Tounga Barou belongs to Benin;
15. Gandégabi Barou Kaïna belongs to Benin;
16. Gandégabi Barou Béri belongs to Niger;
17. Guirawa Barou, also known as Issa Kaïna, belongs to Niger;

18. Dan Koré Guirawa, also known as Bédari, belongs to Benin;

19. Barou Elhadji Dan Djoda, also known as Sabonbarou or Wéra
Barou, belongs to Benin;
20. Koundou Barou belongs to Benin;

21. Elhadji Chaïbou Barou Béri belongs to Niger;
22. Elhadji Chaïbou Barou Kaïna belongs to Niger;
23. Goussou Barou, also known as Gattawani Béri Barou or Dandani-
koye Barou, belongs to Niger;
24. Beyo Barou, also known as Wéra Kaïna Barou, belongs to Niger;

25. Dolé Barou, also known as Barou Béri or Bani Koubaye, belongs to
Niger.

These various islands are shown on the illustrative sketch-map referred
to in paragraph 115 above.
118. Finally, the Chamber observes that the determination in regard

54141 DIFFÉREND FRONTALIER (ARRÊT )

nance des îles à laquelle elle vient de procéder est sans préjudice de tous
droits privés qui pourraient être détenus sur celles-ci.

**

119. Le Niger a également prié la Chambre de déterminer le tracé de la
frontière sur les deux ponts entre Gaya (Niger) et Malanville (Bénin). Le

Bénin soutient que la question n’entre pas dans le cadre du différend sou-
mis à la Chambre aux termes du compromis et que la Chambre n’a donc
pas compétence pour donner suite à la demande du Niger.
120. La Chambre relève à cet égard que, dans le compromis, «[l]a
Cour est priée de ... déterminer le tracé de la frontière ... dans le secteur

du fleuve Niger». Les ponts entre Gaya et Malanville étant situés dans ce
secteur, la Chambre estime qu’elle a compétence pour déterminer le tracé
de la frontière sur ceux-ci.
121. Le Niger affirme que la frontière passe au milieu de chacun des
ponts. Il fait observer que la construction et l’entretien de ces structures
ont été financés à parts égales par les Parties et qu’elles leur appar-

tiennent conjointement. Selon le Niger, il en découle logiquement que le
tracé de la frontière passe au centre de ces ouvrages, qui sont propriété
conjointe des Parties, et ne suit pas la ligne frontalière dans le fleuve lui-
même. Il prétend en outre que la formule qu’il propose a été adoptée
dans un grand nombre d’accords antérieurs ou actuellement en vigueur.

122. Le Bénin soutient pour sa part que les arrangements convenus
pour la construction et l’entretien des ponts et toute disposition relative à
la propriété conjointe de ceux-ci sont sans rapport avec les questions de
souveraineté territoriale. Il affirme en outre qu’une absence de correspon-
dance entre le tracé de la frontière sur les ponts et son tracé dans le fleuve

au-dessous de ces structures serait illogique et conduirait à des incohé-
rences juridiques.
123. La Chambre observe tout d’abord que les deux ponts qui enjam-
bent le fleuve Niger, joignant Gaya et Malanville, ont été construits res-
pectivement en 1958 et en 1988-1989. Ils mesurent plus de 300 mètres de

long et relient des plates-formes construites sur chacune des rives, qui
sont utilisées par les douanes et d’autres administrations.
La Chambre fait en outre observer qu’il existe plusieurs arrangements
aux termes desquels l’utilisation et l’entretien de ces ponts doivent être
financés à égalité par les deux Parties, qui en sont conjointement pro-
priétaires.

Elle note enfin que ces accords et arrangements ne contiennent aucune
disposition relative à des questions territoriales.
124. La Chambre relève qu’aucune des Parties n’a évoqué l’existence
d’une règle de droit international coutumier relative à la délimitation ter-
ritoriale dans le cas de ponts enjambant des cours d’eau internationaux.

Elle constate également que les divers précédents mentionnés au dossier
sont tous fondés sur des accords bilatéraux.
La Chambre observera qu’au vu de l’absence d’accord entre les Parties

55 FRONTIER DISPUTE (JUDGMENT ) 141

to the attribution of islands effected above is without prejudice to any
private law rights which may be held in respect of those islands.

**

119. Niger has also asked the Chamber to determine the frontier on
the two bridges between Gaya (Niger) and Malanville (Benin). Benin

contends that this issue is not covered by the dispute submitted to
the Chamber under the terms of the Special Agreement and that the
Chamber therefore has no jurisdiction to comply with Niger’s request.
120. The Chamber notes in this regard that, in the Special Agreement,
“[t]he Court is requested to . . . determine the course of the boundary . . .

in the River Niger sector”. Since the bridges between Gaya and Malan-
ville are located in that sector, the Chamber considers that it has juris-
diction to determine where the boundary is located on these bridges.
121. Niger contends that the boundary is situated at the middle point
of each of the bridges. It observes that the construction and maintenance
of these structures has been financed by the Parties on an equal basis and

that the bridges are their joint property. According to Niger, it logically
follows that the boundary is situated at the middle point of this joint
property and does not follow the boundary line in the river itself. Niger
further contends that this solution has been adopted in a substantial
number of previous and existing agreements.

122. Benin, for its part, submits that the arrangements for the con-
struction and maintenance of the bridges and any provisions on joint
ownership bear no relation to the issue of territorial sovereignty. It
further contends that a difference between the location of the boundary
on the bridges and the course of the boundary in the river beneath would

be incoherent and lead to legal inconsistencies.

123. The Chamber initially observes that the two bridges crossing the
River Niger between Gaya and Malanville were built in 1958 and 1988-
1989 respectively. They are more than 300 m in length and they connect

platforms built on each of the banks, which are used for customs and
other administrative purposes.
The Chamber further observes that there are a number of arrange-
ments in place which provide that the use and maintenance of these
bridges, of which the Parties have joint ownership, is to be financed by
them on an equal basis.

It finally observes that these agreements and arrangements do not con-
tain any provisions on territorial issues.
124. The Chamber notes that neither of the Parties has contended that
there is a rule of customary international law regarding territorial delimi-
tation in the case of bridges over international watercourses. It further

notes that the various precedents cited in the case file are all based on
bilateral agreements.
The Chamber observes that, in the absence of an agreement between

55142 DIFFÉREND FRONTALIER (ARRÊT )

la solution à retenir est celle du report vertical de la frontière tracée sur le
cours d’eau. Cette solution est conforme à la conception générale selon

laquelle une frontière marque la séparation des souverainetés étatiques,
autant sur la surface terrestre que dans le sous-sol et l’espace atmosphé-
rique surjacent. En outre, la solution du report vertical de la frontière tra-
cée sur le cours d’eau permet de pallier les difficultés que pourrait engen-
drer l’existence de deux limites distinctes se trouvant sur des plans

géométriques très proches l’un de l’autre.
Au vu de ce qui précède, la Chambre conclut que la frontière sur les
ponts reliant Gaya et Malanville suit le tracé de la frontière dans le
fleuve. Cette conclusion est sans préjudice de tous les arrangements en
vigueur entre le Bénin et le Niger concernant l’utilisation et l’entretien des

ponts, dont le financement est assuré à égalité par les deux Etats (voir
paragraphe 123 ci-dessus). La Chambre observe en particulier que la
question du tracé de la frontière sur les ponts est entièrement indépen-
dante de celle de la propriété desdits ouvrages, qui appartiennent conjoin-
tement aux Parties.

* * *

125. La Chambre est en outre chargée, en vertu de l’alinéa c) de l’ar-
ticle 2 du compromis, de «déterminer le tracé de la frontière entre les
deux Etats dans le secteur de la rivière Mékrou».

Bien que le Bénin ait soutenu que cette question constituait un «diffé-
rend très artificiel, forgé par [le] Niger lors de la négociation du compro-
mis», à des fins tactiques et alors que jamais jusqu’alors les Parties ne
s’étaient opposées entre elles à ce sujet — ce que le Niger a fermement
contesté —, il n’est pas douteux qu’il entre bien dans la mission de la

Chambre, aux termes mêmes du compromis, de trancher cet aspect du
litige, sans avoir à spéculer sur les arrière-pensées de l’une ou de l’autre
Partie. Le Bénin n’a d’ailleurs pas prétendu qu’il puisse en aller autre-
ment.

**

126. Les Parties s’opposent, en ce qui concerne la frontière dans ce sec-
teur, dans les termes suivants.
Selon le Bénin, la frontière suivrait la ligne médiane de la rivière
Mékrou. Cela résulterait, d’une part, de l’application du principe de l’uti

possidetis juris, dès lors qu’à la date des indépendances les territoires du
Dahomey et du Niger étaient séparés par le cours de cette rivière, en
vertu des titres juridiques en vigueur aussi bien que des effectivités;
d’autre part, et en tout état de cause, une telle frontière s’imposerait du
fait de la reconnaissance formelle par le Niger, à l’occasion des négocia-

tions conduites entre les deux Parties en vue de la construction du bar-
rage de Dyodyonga en 1973 et 1974, de ce que la Mékrou constituait bien
la limite entre leurs territoires respectifs. A cet égard, le Bénin se prévaut

56 FRONTIER DISPUTE (JUDGMENT ) 142

the Parties, the solution is to extend vertically the line of the boundary on
the watercourse. This solution accords with the general theory that a

boundary represents the line of separation between areas of State sov-
ereignty, not only on the earth’s surface but also in the subsoil and in the
superjacent column of air. Moreover, the solution consisting of the ver-
tical extension of the boundary line on the watercourse avoids the diffi-
culties which could be engendered by having two different boundaries on

geometrical planes situated in close proximity to one another.
In light of the foregoing, the Chamber concludes that the boundary on
the bridges between Gaya and Malanville follows the course of the
boundary in the river. This finding is without prejudice to the arrange-
ments in force between Benin and Niger regarding the use and mainte-

nance of these bridges, which are financed by the two States on an equal
basis (see paragraph 123 above). The Chamber observes in particular
that the question of the course of the boundary on the bridges is totally
independent of that of the ownership of those structures, which belong to
the Parties jointly.

* * *

125. The Chamber is further charged under Article 2 (c) of the Special
Agreement with “determin[ing] the course of the boundary between the
two States in the River Mekrou sector”.

Although Benin contended that this issue was a “quite artificial dispute
created by Niger at the time of negotiation of the Special Agreement” for
tactical purposes and that until then there had never been any disagree-
ment between the Parties on the matter — an assertion which Niger
strongly denied —, there can be no doubt that the Chamber’s task,

according to the express terms of the Special Agreement, includes settle-
ment of this aspect of the dispute, without having to speculate on the
motives of either Party. Indeed Benin has not sought to argue otherwise.

**

126. The dispute between the Parties in regard to this sector of the
boundary may be summarized as follows.
According to Benin, the boundary follows the median line of the River
Mekrou. That is said to result, on the one hand, from the application of

the uti possidetis juris principle, since, at their dates of independence, the
territories of Dahomey and Niger were separated by the course of that
river pursuant both to the legal titles in force and to the effectivités ;on
the other hand and in any event, such a boundary is said to have been
confirmed by Niger’s formal recognition, at the time of the negotiations

between the two Parties in 1973 and 1974 with a view to the construction
of the Dyodyonga dam, that the Mekrou did indeed constitute the
boundary between their respective territories. In this connection, Benin

56143 DIFFÉREND FRONTALIER (ARRÊT )

d’une note verbale du Niger en date du 29 août 1973 et d’un procès-ver-
bal de la réunion tenue le 8 février 1974 entre les experts des deux Parties

(voir paragraphe 39 ci-dessus), l’un et l’autre de ces documents désignant
la rivière Mékrou comme constituant la frontière entre les deux Etats.

Selon le Niger, la frontière dans le secteur considéré suivrait une ligne
composée de deux segments: le premier serait une ligne droite reliant le

point situé au confluent de la rivière Mékrou avec le fleuve Niger au point
situé à l’intersection du méridien de Paris et de la chaîne montagneuse de
l’Atakora; le second relierait ce dernier point au point d’intersection des
anciennes limites des cercles de Say et de Fada, d’une part, et de Fada et
de l’Atakora, d’autre part. Cela résulterait de la combinaison des textes

réglementaires ayant fixé, à l’époque coloniale, la limite entre le Daho-
mey et le Niger dans le secteur en cause, à savoir le décret du 2 mars 1907
rattachant les cercles de Fada-N’Gourma et de Say à la colonie du Haut-
Sénégal et Niger (à laquelle le Niger a succédé) et ceux du 12 août 1909 et
du 23 avril 1913 (voir paragraphe 39 ci-dessus) modifiant la limite de
cette dernière colonie avec le Dahomey. Quant aux documents de 1973 et

1974 invoqués par le Bénin, le Niger soutient qu’à supposer que l’on
puisse y déceler un engagement juridique, ce dernier serait entaché d’une
erreur manifeste de nature à le priver de validité en vertu des règles de
droit coutumier relatives aux vices affectant les accords internationaux,
telles que codifiées au paragraphe 1 de l’article 48 de la convention de

Vienne sur le droit des traités.

Le croquis n° 5, à la page 144 ci-après, illustre les revendications des
Parties en ce qui concerne la frontière dans le secteur de la rivière
Mékrou.

**

127. Il appartient d’abord à la Chambre de rechercher, par application
du principe de l’uti possidetis juris, quel était le tracé de la limite inter-

coloniale à la date critique des indépendances, en août 1960. C’est ensuite
seulement qu’elle devra, si besoin est, se pencher sur les actes de 1973
et 1974 invoqués par le Bénin, afin de rechercher s’ils ont pu valablement
produire des effets juridiques de nature à affecter le tracé de la frontière
internationale telle qu’elle était antérieurement fixée, c’est-à-dire telle
qu’elle résultait de l’uti possidetis de 1960.

*

128. La détermination du tracé de la limite intercoloniale à la date cri-
tique commande de se tourner d’abord vers les titres juridiques invoqués

par les Parties, les effectivités ne devant intervenir, le cas échéant, qu’à
titre confirmatif ou subsidiaire, conformément aux règles ci-dessus rap-
pelées (voir paragraphes 47 et 77).

57 FRONTIER DISPUTE (JUDGMENT ) 143

relies on a Note Verbale from Niger dated 29 August 1973 and on the
minutes of a meeting held on 8 February 1974 between the experts of the

two Parties (see paragraph 39 above), the River Mekrou being indicated
in both of these documents as constituting the boundary between the two
States.
According to Niger, the boundary in the sector in question follows a
line comprising two parts: the first is a straight line joining the point of

confluence of the River Mekrou with the River Niger to the point where
the Paris meridian meets the Atakora mountain range: the second part
joins this latter point to the point where the former boundary between
the cercles of Say and Fada meets the former boundary between the
cercles of Fada and Atakora. That is claimed to result from the combined

effect of the regulatory instruments which, during the colonial period,
defined the boundary between Dahomey and Niger in the sector in ques-
tion, namely the decree of 2 March 1907 incorporating the cercles of
Fada-N’Gourma and Say into the colony of Haut-Sénégal et Niger (to
which Niger succeeded) and the decrees of 12 August 1909 and 23 April
1913 (see paragraph 39 above) modifying the boundary of the latter

colony with Dahomey. As regards the documents of 1973 and 1974 relied
on by Benin, Niger contends that, even assuming that they can be
regarded as creating a legal obligation, such obligation is vitiated by a
manifest error which would deprive it of any validity according to the
rules of customary law concerning defects in international agreements, as

codified in Article 48, paragraph 1, of the Vienna Convention on the Law
of Treaties.
Sketch-map No. 5, on page 144 below, shows the claims of the Parties
in respect of the boundary in the sector of the River Mekrou.

**

127. The Chamber will first ascertain, by application of the principle
of uti possidetis juris, what the course of the intercolonial boundary was

at the critical dates of independence in August 1960. Only then is it
required, if necessary, to consider the documents of 1973 and 1974 relied
on by Benin in order to determine whether they could validly have pro-
duced legal effects capable of affecting the course of the international
boundary as previously defined, that is to say the boundary resulting
from the uti possidetis of 1960.

*

128. To determine the course of the intercolonial boundary at the criti-
cal date it is necessary to examine first the legal titles relied on by the

Parties, with any effectivités being considered only on a confirmatory or
subsidiary basis, in accordance with the rules recalled above (see para-
graphs 47 and 77).

57144 DIFFÉREND FRONTALIER (ARRÊT )

58FRONTIER DISPUTE (JUDGMENT ) 144

58145 DIFFÉREND FRONTALIER (ARRÊT )

129. Le premier des textes à prendre en considération est le décret sus-
mentionné du 2 mars 1907, ayant pour objet de modifier le tracé de la
limite entre la colonie du Haut-Sénégal et Niger et celle du Dahomey, par
le rattachement des cercles de Fada N’Gourma et de Say, jusqu’alors

attribués er Dahomey, à la colonie voisine. Il résulte des termes de
l’article 1 de ce décret que la nouvelle limite intercoloniale:

«est constituée, à partir de la frontière du Togo, par les limites
actuelles du cercle du Gourma jusqu’à la rencontre de la chaîne
montagneuse de l’Atakora dont elle suit le sommet jusqu’au point
d’intersection avec le méridien de Paris, d’où elle suit une ligne droite
dans la direction du nord-est et aboutissant au confluent de la rivière

Mékrou avec le Niger».
130. Une telle délimitation, dont il est constant qu’elle ne coïncide pas

avec le cours de la rivière Mékrou, tend à conforter la thèse nigérienne.
Aussi bien, d’ailleurs, le Niger soutient-il que le décret du 2 mars 1907,
modifié dans une mesure limitée en 1909 et 1913 (voir paragraphe 39 ci-
dessus), est demeuré en vigueur jusqu’à la date critique des indépen-

dances en 1960, et qu’il constitue le titre juridique auquel il convient
de se référer pour l’application du principe de l’uti possidetis juris.
131. Le Bénin, toutefois, combat cette thèse en affirmant que la déli-
mitation de 1907 a été implicitement remise en cause par le décret du
1er mars 1919 portant création de la colonie de la Haute-Volta, et qu’à

partir de 1919 aucun des actes administratifs successifs concernant le sec-
teur en litige ne s’est référé à la ligne de 1907. Au contraire, tous ces actes,
et notamment l’arrêté du 31 août 1927 par lequel le gouverneur général
de l’AOF fixait les limites des colonies de la Haute-Volta et du Niger,
ont, explicitement ou implicitement, retenu le cours de la Mékrou comme

limite intercoloniale, ce que confirmerait en outre un abondant matériau
cartographique.
132. La Chambre ne peut pas adhérer à l’idée selon laquelle le décret
du 1 er mars 1919 aurait implicitement abrogé ou modifié celui du

2 mars 1907, pour ce qui est de la limite intercoloniale dans le secteur
considéré.
Le décret de 1919 crée la colonie de la Haute-Volta, constituée par le
détachement d’un certain nombre de cercles, dont ceux de Fada
N’Gourma et Say, du Haut-Sénégal et Niger. Il en est résulté que, dans le

secteur de la Mékrou, la colonie du Dahomey ne se trouvait plus être
limitrophe du Haut-Sénégal et Niger, mais de la Haute-Volta nouvelle-
ment créée, si bien que la limite tracée par l’article premier du décret de
1907 ne pouvait plus être présentée comme séparant le Dahomey du

Haut-Sénégal et Niger.
Toutefois, rien ne permet d’inférer des termes du décret de 1919 que ses
auteurs auraient entendu remettre en cause la ligne définie comme limite
intercoloniale en 1907. Les deux cercles détachés en 1907 du Dahomey
pour être inclus dans la colonie voisine du Haut-Sénégal et Niger se sont

trouvés, en 1919, englobés dans la nouvelle colonie de la Haute-Volta.

59 FRONTIER DISPUTE (JUDGMENT ) 145

129. The first text for consideration is the above-mentioned decree of
2 March 1907, the object of which was to change the course of the

boundary between the colony of Haut-Sénégal et Niger and that of
Dahomey by incorporating the cercles of Fada N’Gourma and Say, until
then part of Dahomey, into the neighbouring colony. Article 1 of that
decree provides that the new intercolonial boundary:

“is constituted, from the boundary of Togo, by the present bound-
ary of the cercle of Gourma until it reaches the Atakora mountain
range, whose summit it follows until it meets the Paris meridian,

from which point it runs in a straight line in a north-easterly direc-
tion, terminating at the confluence of the River Mekrou with the
Niger”.

130. That delimitation, which clearly does not coincide with the course
of the River Mekrou, tends to support the position of Niger. Indeed
Niger accordingly contends that the decree of 2 March 1907, as partially
amended in 1909 and 1913 (see paragraph 39 above), remained in force
until the critical dates of independence in 1960 and that it constitutes the

legal title to be relied on for purposes of applying the uti possidetis juris
principle.
131. Benin, however, challenges this position, arguing that the 1907
delimitation was implicitly superseded by the decree of 1 March 1919 cre-
ating the colony of Haute-Volta, and that from 1919 onwards not one of

the successive administrative instruments relating to the disputed sector
mentioned the line of 1907. On the contrary, every one of those instru-
ments, and in particular the arrêté of 31 August 1927, whereby the
Governor-General of the AOF fixed the boundaries of the colonies of
Haute-Volta and Niger, expressly or impliedly adopted the course of

the Mekrou as the intercolonial boundary, as is moreover confirmed by
abundant cartographic evidence.
132. The Chamber cannot accept the proposition that the decree of
1 March 1919 implicitly abrogated or amended that of 2 March 1907 in
relation to the intercolonial boundary in the sector in question.

The 1919 decree created the colony of Haute-Volta, which was consti-
tuted by detaching a certain number of cercles, including Fada N’Gourma
and Say, from Haut-Sénégal et Niger. The effect of this was that, in
the Mekrou sector, the colony of Dahomey, instead of bordering Haut-
Sénégal et Niger, now bordered the newly created Haute-Volta, so that

the boundary established in Article 1 of the 1907 decree could no longer
be considered as separating Dahomey from Haut-Sénégal et Niger.

However, there is nothing in the terms of the 1919 decree to suggest
that its authors intended to call into question the line defined as the inter-

colonial boundary in 1907. The two cercles detached from Dahomey in
1907 in order to be included in the neighbouring colony of Haut-Sénégal
et Niger were in 1919 incorporated into the new colony of Haute-Volta.

59146 DIFFÉREND FRONTALIER (ARRÊT )

Pour autant, la limite séparant ces cercles (et notamment celui de Say) du
Dahomey, n’a pas été déplacée en 1919: ni les termes du décret du
1 mars 1919, ni aucune incompatibilité entre les deux textes successifs ne
conduisent à la conclusion que la limite clairement et précisément dessi-

née en 1907 aurait été modifiée en 1919.
133. Cela ne suffit cependant pas à infirmer la thèse soutenue par le
Bénin quant au tracé de la frontière dans le secteur considéré.
134. La Chambre ne peut tout d’abord manquer de relever que le
décret de 1919 ne se réfère ni dans ses visas ni dans son dispositif à celui

de 1907, et qu’il ne fixe pas précisément, comme le faisait son prédéces-
seur, la limite intercoloniale. En réalité, le décret de 1919 ne définit le ter-
ritoire de la Haute-Volta que par la désignation des cercles qui le com-
posent, et c’est donc aussi de cette manière que sont définies indirectement
les limites entre la Haute-Volta et les colonies voisines, notamment le

Dahomey. C’est par la délimitatier précise des cercles mentionnés à
l’article premier du décret du 1 mars 1919 — délimitation à laquelle ne
procède pas le décret lui-même — que pouvait être définie, à partir de
cette date, la limite intercoloniale. Plus spécialement, c’est la délimitation

du cercle de Say qui devait alors permettre de fixer la limite entre la
Haute-Volta et le Dahomey dans le secteur qui est l’objet du litige. Or,
ainsi qu’il a été rappelé plus haut (voir paragraphes 30, 47 et 71), la
délimitation des cercles, principales subdivisions administratives des
colonies, relevait à cette époque, en vertu de l’article 5 du décret du

18 octobre 1904 portant réorganisation de l’AOF, de la compétence
du gouverneur général. De ce qui précède, il y a lieu de déduire que
si le décret de 1919 ne remettait pas en cause la limite intercoloniale
fixée en 1907, il laissait intacte, pour l’avenir, la possibilité pour le gou-
verneur général de fixer l’étendue des cercles considérés comme il en

avait normalement la compétence.
135. La Chambre note que l’arrêté du gouverneur général du
31 août 1927 retient la rivière Mékrou comme la limite du cercle de Say
dans sa partie contiguë à la colonie du Dahomey.

Cet arrêté a été pris par le gouverneur général à la suite, et en consé-
quence, du décret du 28 décembre 1926 rattachant à la colonie du Niger
(créée quelques années plus tôt) le cercle de Say. Il appartenait alors au
gouverneur général de préciser les limites entre les colonies de la Haute-
Volta et du Niger, dans l’exercice de sa compétence pour fixer l’étendue

des cercles: tel était l’objet de l’arrêté du 31 août 1927. Celui-ci, au para-
graphe 2 de son article premier, définit ainsi la limite entre le cercle de
Say et la Haute-Volta:

«Au sud-ouest [par] une ligne partant approximativement de la
Sirba à hauteur du parallèle de Say pour aboutir à la Mékrou;

Au sud-est, par la Mékrou de ce point jusqu’à son confluent avec

le Niger».

60 FRONTIER DISPUTE (JUDGMENT ) 146

Nonetheless, the boundary separating those cercles (and in particular the
cercle of Say) from Dahomey, was not moved in 1919: nothing in the

terms of the decree of 1 March 1919, nor any incompatibility between
two successive texts, leads to the conclusion that the boundary clearly
and precisely defined in 1907 was modified in 1919.
133. That does not suffice however to refute Benin’s argument with
respect to the course of the boundary in the sector concerned.

134. The Chamber is bound to note, first of all, that the 1919 decree
refers neither in its citations nor in its operative articles to the 1907
decree, and that it does not include any precise definition of the inter-
colonial boundary, as the earlier decree had done. In reality, the 1919
decree defines the territory of Haute-Volta solely by reference to thceercles

which compose it, and it is thus also by this means that it indirectly
defines the boundaries between Haute-Volta and the neighbouring colo-
nies, and in particular Dahomey. It is by the precise delimitation of the
cercles mentioned in Article 1 of the decree of 1 March 1919 — a delimi-
tation not effected by the decree itself — that, from this date, the inter-
colonial boundary could be defined. In particular, it was the delimitation

of the cercle of Say that would then enable the boundary between Haute-
Volta and Dahomey to be determined in the disputed sector. However, as
recalled above (see paragraphs 30, 47 and 71), the delimitation of the
cercles, the principal administrative subdivisions of the colonies, was at
that time, pursuant to Article 5 of the decree of 18 October 1904 reorganiz-

ing the AOF, a matter falling within the competence of the Governor-
General. It must therefore be concluded from the foregoing that, while the
1919 decree did not call into question the intercolonial boundary deter-
mined in 1907, it left unaffected the power of the Governor-General to
modify the boundary in the future by fixing the boundaries of the cercles

in question in accordance with his normal competence in that regard.
135. The Chamber notes that the arrêté of the Governor-General of
31 August 1927 defines the River Mekrou as the boundary of the cercle
of Say in the area contiguous with the colony of Dahomey.
That arrêté was adopted by the Governor-General following, and as a

consequence of, the decree of 28 December 1926 incorporating the cercle
of Say into the colony of Niger (created some years earlier). It was thus
for the Governor-General to define the boundaries between the colonies
of Haute-Volta and Niger, in the exercise of his power to define the
boundaries of the cercles: that was the purpose of the arrêté of 31 August
1927. That instrument, in the second paragraph of Article 1, defined the

boundary between the cercle of Say and Haute-Volta in the following
terms:

“In the South-West [by] a line starting approximately from the
[River] Sirba at the level of the Say parallel and terminating at the

Mekrou;
In the South-East, by the Mekrou from that point as far as its
confluence with the Niger.”

60147 DIFFÉREND FRONTALIER (ARRÊT )

Ainsi, par cet arrêté, le gouverneur général fixe clairement la limite du
cercle de Say, et par suite la limite intercoloniale, à la Mékrou.

136. Il est vrai, et le Niger n’a pas manqué de le relever, que cet arrêté
du 31 août 1927 a donné lieu, le 15 octobre suivant, à un erratum qui en
modifie le libellé, de manière par définition rétroactive, en en faisant dis-
paraître la référence au cours de la Mékrou comme limite au sud-est entre
le cercle de Say et la Haute-Volta. L’article premier de l’arrêté, dans sa

rédaction résultant de l’erratum du 15 octobre, se borne à indiquer que la
limite entre le Niger et la Haute-Volta «remonte ... le cours de la Tapoa
jusqu’au point où elle rencontre l’ancienne limite des cercles de Fada et
de Say, qu’elle suit jusqu’à son intersection avec le cours de la Mékrou».
Toutefois l’erratum semble bien avoir été motivé, non pas par la cir-

constance que le gouverneur général n’entendait pas fixer la limite sud-est
du cercle de Say au cours de la Mékrou, mais par la volonté de ne pas
préciser la limite entre le Dahomey et le Niger dans un arrêté ayant pour
objet, comme cela résultait de son intitulé même, de fixer la limite entre le
Niger et la Haute-Volta. Non seulement l’erratum n’aurait-il ainsi pas
démenti que les limites du cercle de Say étaient telles qu’indiquées au mois

d’août précédent, mais il a par ailleurs confirmé explicitement que le point
d’aboutissement de la limite sud de ce cercle se situait sur la Mékrou.
137. Il y a en outre lieu pour la Chambre de prêter attention aux textes
relatifs à la création de réserves de chasse et de parcs nationaux dans la
région dite «du W du Niger». Tant l’arrêté du gouverneur général du

16 avril 1926, que les arrêtés du 30 septembre 1937 du gouverneur du
Dahomey et du 13 novembre suivant du gouverneur du Niger — définis-
sant, sur le territoire de chacune des deux colonies, l’étendue provisoire
des réserves naturelles — ou encore les arrêtés du gouverneur général du
3 décembre 1952 et du 25 juin 1953 fixant définitivement les limites des-

dites réserves, retiennent la rivière Mékrou en vue de la délimitation des
aires considérées. On voit mal, si la Mékrou ne constituait pas, aux yeux
des autorités administratives compétentes pour édicter les arrêtés en
cause, la limite intercoloniale, pourquoi son cours aurait été retenu
comme limite des parcs nationaux et réserves naturelles en cause.

138. Enfin, la Chambre ne peut pas manquer de constater que les élé-
ments cartographiques versés au dossier confirment nettement que, à
partir de 1926-1927 en tout cas, la Mékrou était généralement regardée
comme la limite intercoloniale par l’ensemble des administrations et ins-
titutions de la puissance coloniale.
Sans doute les cartes — sauf si, annexées à un acte administratif, elles

en forment partie intégrante, ce qui n’est pas le cas en l’espèce — n’ont-
elles que la portée relative que leur confère la jurisprudence rappelée plus
haut (voir paragraphe 44). Mais en l’occurrence, le matériau cartogra-
phique peut être retenu comme confirmant et confortant les conclusions
auxquelles conduit l’analyse des textes réglementaires susmentionnés. Il

en va ainsi notamment de la carte dressée et publiée en octobre 1926 par
le service géographique de l’AOF (connue sous le nom de «carte Blon-
del la Rougery»), de la carte intitulée «Nouvelle frontière de la Haute-

61 FRONTIER DISPUTE (JUDGMENT ) 147

Thus, by this arrêté the Governor-General clearly fixed the boundary of
the cercle of Say, and hence the intercolonial boundary, on the Mekrou.

136. It is true, and Niger has been at pains to point this out, that the
arrêté of 31 August 1927 was followed on 15 October by an erratum
amending its text retroactively by removing the reference to the course of
the Mekrou as the south-eastern boundary between the cercle of Say and
Haute-Volta. Article 1 of the arrêté, as amended pursuant to the erratum

of 15 October, confines itself to stating that the boundary between the
Niger and Haute-Volta “follows . . . the course of the Tapoa upstream
until it meets the former boundary between the cercles of Fada and Say,
which it follows as far as its intersection with the course of the Mekrou”.
However, the erratum would seem in effect to have been motivated

not by the fact that the Governor-General did not mean to fix the south-
eastern boundary of the cercle of Say along the Mekrou, but rather by a
wish not to define the boundary between Dahomey and Niger in anarrêté
whose purpose, as was clear from its title, was to fix the boundary
between Niger and Haute-Volta. Not only did theerratum thus not contra-
dict the fact that the boundaries of the cercle of Say were as indicated the

previous August, but it expressly confirmed that the terminal point of the
southern boundary of that cercle was situated on the Mekrou.
137. Furthermore, the Chamber must take account of the instruments
concerning the creation of game reserves and national parks in the area
known as “The Niger W”. Both the Governor-General’s arrêté of 16 April

1926 and the arrêtés of 30 September 1937 of the Governor of Dahomey
and of 13 November of the same year of the Governor of Niger — defin-
ing within the territory of each of the two colonies the provisional extent
of their nature reserves — as well as the Governor-General’s arrêtés of
3 December 1952 and 25 June 1953 definitively fixing the borders of those

reserves, use the River Mekrou for purposes of delimitation of the areas
in question. If, in the eyes of the administrative authorities competent to
promulgate the arrêtés in question, the Mekrou did not represent the
intercolonial boundary, it is difficult to see why it should have been
chosen as the boundary of these national parks and nature reserves.

138. Finally, the Chamber is bound to note that the cartographic
material in the file clearly confirms that, certainly from 1926-1927, the
Mekrou was generally regarded as the intercolonial boundary by all the
administrative authorities and institutions of the colonial Power.

Certainly, maps — unless they are annexed to an administrative instru-

ment, and hence form an integral part thereof, which is not the case
here — possess only the relative force conferred upon them by the juris-
prudence recalled above (see paragraph 44). However, in the present case
the cartographic evidence may be regarded as confirming and reinforcing
the conclusions flowing from an analysis of the above-mentioned regula-

tive texts. The same applies notably to the map prepared and published
in October 1926 by the AOF Geographical Service (known as the “Blon-
del la Rougery map”), to the map entitled “New Boundary of Haute-

61148 DIFFÉREND FRONTALIER (ARRÊT )

Volta et du Niger (suivant l’erratum du 5 octobre 1927 à l’arrêté du 31 août
1927)», ou encore de la carte routière Dahomey-Togo établie par le ser-

vice géographique de l’AOF en 1938 (voir paragraphe 42 ci-dessus).
139. L’ensemble de ces considérations conforte la thèse selon laquelle
la ligne de 1907 ne correspondait plus, à la date critique, à la limite inter-
coloniale et qu’au contraire, à cette date, c’est le cours de la Mékrou qui,
selon l’opinion de l’ensemble des autorités compétentes de l’administra-

tion coloniale, constituait la limite entre les colonies voisines — alors
celles du Dahomey et du Niger.
140. La Chambre observe que, ainsi que l’a soutenu le Niger, le décret
du 2 mars 1907, qui définissait nettement une limite différente, n’a jamais
été expressément abrogé ou modifié, et qu’il n’a pas non plus été sup-

planté par un autre texte de valeur au moins égale — soit un décret ou
une loi — qui aurait comporté des dispositions clairement incompatibles
avec les siennes. Aucun texte de ce genre n’a d’ailleurs été mentionné par
le Bénin en réponse à une question de la Chambre portant sur cet aspect
du différend, hormis le décret de 1919 dont il a été expliqué plus haut
pourquoi il n’avait pas la portée abrogative que lui prête la thèse

béninoise.
Mais, outre ce qui a été dit ci-dessus (voir paragraphe 134) sur la com-
pétence du gouverneur général pour fixer les limites des cercles et, par-
tant, pour préciser celles des colonies, la Chambre se doit de souligner
que le principe de l’uti possidetis juris suppose non seulement de se réfé-

rer aux titres juridiques en vigueur, mais aussi de prendre en compte la
manière dont ces titres étaient interprétés et appliqués par les autorités
publiques compétentes de la puissance coloniale, notamment dans l’exer-
cice de leur pouvoir normatif. Force est de constater que les actes admi-
nistratifs édictés à partir de 1927 n’ont fait l’objet d’aucune contestation

devant les juridictions compétentes, et qu’il n’apparaît pas qu’il ait jamais
été reproché à l’administration coloniale, à l’époque, de s’être indûment
écartée du tracé résultant du décret de 1907. Il n’appartient pas à la
Chambre de se substituer au juge interne (en l’espèce, le juge administra-
tif français) en exerçant son propre contrôle de légalité sur les actes en

cause, au regard du décret de 1907, ni de spéculer sur ce qu’auraient pu
décider les juridictions françaises si elles avaient été saisies. Le fait est
qu’elles ne l’ont pas été, et que rien ne permet d’affirmer que les autorités
administratives qui ont statué à partir de 1927 auraient soit manifeste-
ment excédé leurs compétences, soit manifestement méconnu les règles
applicables.

*

141. Il résulte de tout ce qui précède que, à partir de 1927 en tout cas,
les autorités administratives compétentes ont considéré le cours de la

Mékrou comme la limite intercoloniale séparant le Dahomey du Niger,
que ces autorités ont traduit cette délimitation dans les actes successifs
qu’elles ont édictés à partir de 1927, lesquels indiquent, pour les uns, et

62 FRONTIER DISPUTE (JUDGMENT ) 148

Volta and Niger (according to the erratum of 5 October 1927 to the
arrêté of 31 August 1927)” and to the Dahomey-Togo roadmap prepared

by the AOF Geographical Service in 1938 (see paragraph 42 above).
139. All of the foregoing considerations confirm the position that the
1907 line no longer corresponded, at the critical date, to the intercolonial
boundary and that, on the contrary, at that date, it was the course of
the Mekrou which, in the view of all the competent authorities of the

colonial administration, constituted the boundary between the adjacent
colonies — at that date the colonies of Dahomey and Niger.
140. The Chamber observes that, as argued by Niger, the decree of
2 March 1907, which clearly defined a different boundary, was never
expressly abrogated or amended, or indeed superseded by some other

instrument of at least equal authority — either a decree or a statute —
containing provisions clearly incompatible with its own. Nor indeed was
any instrument of this kind cited by Benin in reply to a question from the
Chamber on this aspect of the dispute, with the exception of the
1919 decree, which, as explained above, did not have the abrogating
effect claimed for it by Benin.

However, further to what has already been said (see paragraph 134) in
regard to the power of the Governor-General to fix the boundaries of the
cercles and, hence, to determine those of colonies, the Chamber would
emphasize that the uti possidetis juris principle requires not only that reli-

ance be placed on existing legal titles, but also that account be taken of
the manner in which those titles were interpreted and applied by the com-
petent public authorities of the colonial Power, in particular in the exer-
cise of their law-making power. The Chamber is bound to note that the
administrative instruments promulgated after 1927 were never the subject

of any challenge before the competent courts, and that there is no evi-
dence that the colonial administration was ever criticized at the time for
having improperly departed from the line resulting from the 1907 decree.
It is not for the Chamber to substitute itself for a domestic court (in this
case, the French administrative courts) by carrying out its own review of

the legality of the instruments in question in light of the 1907 decree, nor
to speculate on what the French courts might have decided had they been
seised of the matter. The fact is that they were not so seised and that
there is nothing to suggest that, in the decisions taken by them after 1927,
the administrative authorities either manifestly exceeded their powers or
acted in manifest breach of the applicable rules.

*

141. It follows from all of the foregoing that, at least from 1927
onwards, the competent administrative authorities regarded the course of

the Mekrou as the intercolonial boundary separating Dahomey from
Niger, that those authorities reflected that boundary in the successive
instruments promulgated by them after 1927, some of which expressly

62149 DIFFÉREND FRONTALIER (ARRÊT )

supposent nécessairement, pour les autres, une telle limite, et que tel était
l’état du droit à la date des indépendances en août 1960. Dans ces condi-

tions, il n’est pas nécessaire de rechercher d’éventuelles effectivités en vue
d’appliquer le principe de l’uti possidetis, les effectivités ne pouvant pré-
senter un intérêt, en la matière, que pour compléter ou suppléer des titres
juridiques incertains ou absents, mais ne pouvant jamais prévaloir sur des
titres auxquels elles seraient contraires. La Chambre constate, d’ailleurs,

et de façon surabondante, que les Parties n’ont invoqué au cours des
débats que d’assez faibles effectivités dans le secteur considéré.

**

142. Eu égard à la conclusion qui précède, le débat qui a opposé les
Parties au sujet de la portée juridique de la note verbale du Niger en date
du 29 août 1973 et du procès-verbal de la réunion d’experts en date du

8 février 1974 devient sans objet. Il n’y a donc pas lieu de trancher les
questions de savoir si de tels actes auraient pu constituer un engagement
juridiquement contraignant pour le Niger et, dans l’affirmative, si la vali-
dité dudit engagement aurait pu être viciée par une erreur répondant aux
conditions fixées par le droit international coutumier.

**

143. Il reste enfin à la Chambre de déterminer à quel endroit précis de
la rivière Mékrou est située la frontière entre le Bénin et le Niger. A cet
égard, le Bénin lui a demandé, dans ses conclusions finales, de dire et
juger que la frontière suit, dans ce secteur, «la ligne médiane de la rivière
Mékrou». Le Niger n’a pas explicitement pris position sur cette question,

même à titre subsidiaire; dans ses écritures, il a cependant soutenu que le
point de départ oriental de la frontière dans ce secteur (qui correspond au
point d’aboutissement occidental de la frontière dans le secteur du fleuve
Niger) serait constitué par le «confluent du fleuve Niger avec la Mékrou»,
qu’il situe à «l’intersection du thalweg de la rivière Mékrou avec le chenal

principal du fleuve Niger» ou au «point d’intersection des axes du fleuve
Niger et de la rivière Mékrou».

144. La Chambre rappellera que, dans l’affaire relative à l’Ile de Kasi-
kili/Sedudu (Botswana/Namibie) , la Cour a fait observer que

«[l]es traités ou conventions qui définissent des frontières dans des
cours d’eau désignent généralement aujourd’hui le thalweg comme
frontière lorsque le cours d’eau est navigable et la ligne médiane

entre les deux rives lorsqu’il ne l’est pas, sans que l’on puisse toute-
fois constater l’existence d’une pratique totalement cohérente en la
matière» (C.I.J. Recueil 1999 (II) , p. 1062, par. 24).

En l’espèce, la Chambre note que, lors d’une mission de reconnaissance
effectuée en avril 1998, le comité technique paritaire de la commission
mixte paritaire bénino-nigérienne de délimitation de la frontière avait

63 FRONTIER DISPUTE (JUDGMENT ) 149

indicated that boundary, whilst others necessarily implied it, and that this
was the state of the law at the dates of independence in August 1960.

In these circumstances, it is unnecessary to look for any effectivités in
order to apply the uti possidetis principle, since effectivités can only be of
interest in a case in order to complete or make good doubtful or absent
legal titles, but can never prevail over titles with which they are at vari-
ance. The Chamber notes moreover, ex abundanti, that the effectivités

relied on by the Parties in the sector in question are relatively weak.

**

142. In the light of the preceding conclusion, the dispute between the
Parties regarding the legal effect of Niger’s Note Verbale of 29 August
1973 and of the minutes of the meeting of experts of 8 February 1974

becomes moot. It is thus unnecessary to decide whether those documents
could have constituted a legally binding obligation for Niger and, if so,
whether that obligation could have been vitiated by an error fulfilling the
conditions laid down by customary international law.

**

143. Lastly, it remains for the Chamber to determine the exact loca-
tion in the River Mekrou of the boundary between Benin and Niger. In
this respect, in its final submissions Benin requested the Chamber to
adjudge and declare that, in this sector, the boundary follows “the
median line of the River Mekrou”. Niger did not expressly adopt a posi-

tion on this question, even on an alternative basis; it did, however, con-
tend in its written pleadings that the eastern starting point of the bound-
ary in that sector (corresponding to the western terminal point of the
boundary in the River Niger sector) is constituted by the “confluence of
the River Niger with the Mekrou”, which it locates at “the intersection of

the thalweg of the River Mekrou with the main channel of the River
Niger” or at the “point of intersection of the axes of the River Niger and
the River Mekrou”.
144. The Chamber would recall that, in the case concerning Kasikili/
Sedudu Island (Botswana/Namibia) , the Court observed that:

“Treaties or conventions which define boundaries in watercourses
nowadays usually refer to the thalweg as the boundary when the
watercourse is navigable and to the median line between the two

banks when it is not, although it cannot be said that practice has
been fully consistent.” (I.C.J. Reports 1999 (II) , p. 1062, para. 24.)

In the present case, the Chamber notes that, during a reconnaissance
mission carried out in April 1998, the joint technical committee of the
Joint Benin-Niger Boundary Delimitation Commission

63150 DIFFÉREND FRONTALIER ARRÊT )

«relevé les coordonnées du point d’intersection des axes du fleuve
Niger et de la rivière Mékrou, mais qu’il n’a[vait] pas pu poursuivre
ses travaux au-delà de ce point du fait que la navigation sur la rivière

Mékrou n’[était] pas possible en raison de la décrue»
Les Parties n’ont d’ailleurs soumis à la Chambre aucun document qui

permettrait d’identifier le tracé exact du thalweg de la Mékrou. La
Chambre note qu’il existe vraisemblablement une différence négligeable
entre les tracés du thalweg et de la ligne médiane de cette rivière, mais
considère qu’une limite suivant la ligne médiane de la Mékrou

répondrait mieux, compte tenu des circonstances, y compris le fait que la
rivière n’est pas navigable, aux exigences de sécurité juridique propres à
la détermination d’une frontière internationale.

145. La Chambre conclut, par les motifs qui précédent, que, dans le

secteur de la rivière Mékrou, la frontière entre le Bénin et le Niger est
constituée par la ligne médiane de ladite rivière.

*
* *
146. Par ces motifs,

L A CHAMBRE ,

1) Par quatre voix contre une,

Dit que la frontière entre la République du Bénin et la République du
Niger dans le secteur du fleuve Niger suit le tracé suivant:

— la ligne des sondages les plus profonds du chenal navigable principal
de ce fleuve, à partir de l’intersection de ladite ligne avec la ligne
médiane de la rivière Mékrou, jusqu’au point de coordonnées

11°52′29″ de latitude nord et 3°25′34″ de longitude est;
— à partir de ce point, la ligne des sondages les plus profonds du chenal
navigable gauche, jusqu’au point de coordonnées 11°51′55″ de lati-
tude nord et 3°27′41″ de longitude est, où la frontière s’écarte de ce

chenal et passe à gauche de l’île de Kata Goungou, pour rejoindre
ensuite le chenal navigable principal au point de coordonnées
11°51′41″ de latitude nord et 3°28′53″ de longitude est;

— à partir de ce dernier point, la ligne des sondages les plus profonds du
chenal navigable principal du fleuve jusqu’à la frontière des Parties
avec le Nigéria;

et que la ligne frontière passe, d’amont en aval, par les points, numérotés
de 1 à 154, dont les coordonnées sont indiquées au paragraphe 115 du
présent arrêt;

POUR : M. Ranjeva, vice-président de la Cour, président de la Chambre ;
MM. Kooijmans, Abraham, juges; M. Bedjaoui, juge ad hoc;
CONTRE : M. Bennouna, juge ad hoc;

64 FRONTIER DISPUTE (JUDGMENT ) 150

“plotted the co-ordinates of the point of intersection of the axes of
the River Niger and River Mekrou, but was not able to continue its
work beyond that point because navigation on the River Mekrou

[was] not possible due to the low water level”.
Moreover, the Parties did not provide the Chamber with any docu-

ments that would enable the exact course of the thalweg of the Mekrou
to be identified. The Chamber notes that in all likelihood there is a neg-
ligible difference between the course of the thalweg and the course of the
median line of the River Mekrou, but considers that, in view of the cir-

cumstances, including the fact that the river is not navigable, a boundary
following the median line of the Mekrou would more satisfactorily meet
the requirement of legal security inherent in the determination of an
international boundary.
145. The Chamber concludes, for the foregoing reasons, that, in the

sector of the River Mekrou, the boundary between Benin and Niger is
constituted by the median line of that river.

*
* *
146. For these reasons,

T HE C HAMBER ,

(1) By four votes to one,

Finds that the boundary between the Republic of Benin and the
Republic of Niger in the River Niger sector takes the following course:

— the line of deepest soundings of the main navigable channel of that
river, from the intersection of the said line with the median line of the
River Mekrou until the point situated at co-ordinates 11°52′29″ lati-

tude North and 3°25′34″ longitude East;
— from that point, the line of deepest soundings of the left navigable
channel until the point located at co-ordinates 11°51′55″ latitude
North and 3°27′41″ longitude East, where the boundary deviates

from this channel and passes to the left of the island of Kata Goungou,
subsequently rejoining the main navigable channel at the point located
at co-ordinates 11°51′41″ latitude North and 3°28′53″ longitude
East;

— from this latter point, the line of deepest soundings of the main navi-
gable channel of the river as far as the boundary of the Parties with
Nigeria;

and that the boundary line, proceeding downstream, passes through the
points numbered from 1 to 154, the co-ordinates of which are indicated
in paragraph 115 of the present Judgment;

IN FAVOUR : Judge Ranjeva, Vice-President of the Court, President of the
Chamber; Judges Kooijmans, Abraham; Judge ad hoc Bedjaoui;
AGAINST: Judge ad hoc Bennouna;

64151 DIFFÉREND FRONTALIER (ARRÊT )

2) Par quatre voix contre une,

Dit qu’en conséquence les îles situées sur le fleuve Niger appartiennent
à la République du Bénin ou à la République du Niger ainsi qu’indiqué

au paragraphe 117 du présent arrêt;
POUR : M. Ranjeva, vice-président de la Cour, président de la Chambre ;
MM. Kooijmans, Abraham, juges; M. Bedjaoui, juge ad hoc;

CONTRE : M. Bennouna, juge ad hoc;

3) Par quatre voix contre une,

Dit que la frontière entre la République du Bénin et la République du
Niger sur les ponts reliant Gaya et Malanville suit le tracé de la frontière
dans le fleuve;

POUR : M. Ranjeva, vice-président de la Cour, président de la Chambre ;
MM. Kooijmans, Abraham, juges; M. Bedjaoui, juge ad hoc;
CONTRE : M. Bennouna, juge ad hoc;

4) A l’unanimité,

Dit que la frontière entre la République du Bénin et la République du
Niger dans le secteur de la rivière Mékrou suit la ligne médiane de cette
rivière, à partir de l’intersection de cette ligne avec la ligne des sondages

les plus profonds du chenal navigable principal du fleuve Niger, jusqu’à
la frontière des Parties avec le Burkina Faso.

Fait en français et en anglais, le texte français faisant foi, au Palais de
la Paix, à La Haye, le douze juillet deux mille cinq, en trois exemplaires,
dont l’un restera déposé aux archives de la Cour et les autres seront
transmis respectivement au Gouvernement de la République du Bénin et

au Gouvernement de la République du Niger.

Le président de la Chambre,

(Signé) Raymond R ANJEVA .

Le greffier,
(Signé) Philippe C
OUVREUR .

M. le juge ad hoc B ENNOUNA joint à l’arrêt l’exposé de son opinion
dissidente.

(Paraphé) R.R.

(Paraphé) Ph.C.

65 FRONTIER DISPUTE (JUDGMENT ) 151

(2) By four votes to one,

Finds that the islands situated in the River Niger therefore belong to
the Republic of Benin or to the Republic of Niger as indicated in para-

graph 117 of the present Judgment;
IN FAVOUR : Judge Ranjeva, Vice-President of the Court, President of the
Chamber; Judges Kooijmans, Abraham; Judge ad hoc Bedjaoui;

AGAINST : Judge ad hoc Bennouna;

(3) By four votes to one,

Finds that the boundary between the Republic of Benin and the
Republic of Niger on the bridges between Gaya and Malanville follows
the course of the boundary in the river;

IN FAVOUR : Judge Ranjeva, Vice-President of the Court, President of the
Chamber; Judges Kooijmans, Abraham; Judge ad hoc Bedjaoui;
AGAINST : Judge ad hoc Bennouna;

(4) Unanimously,

Finds that the boundary between the Republic of Benin and the
Republic of Niger in the River Mekrou sector follows the median line of
that river, from the intersection of the said line with the line of deepest

soundings of the main navigable channel of the River Niger as far as the
boundary of the Parties with Burkina Faso.

Done in French and in English, the French text being authoritative, at
the Peace Palace, The Hague, this twelfth day of July, two thousand and
five, in three copies, one of which will be placed in the archives of the
Court and the others transmitted to the Government of the Republic of

Benin and the Government of the Republic of Niger, respectively.

(Signed) President of the Chamber.(Signed) Raymond R ANJEVA ,

President of the Chamber.

(Signed) Philippe C OUVREUR ,
Registrar.

Judge ad hoc B ENNOUNA appends a dissenting opinion to the Judgment
of the Chamber.

(Initialled) R.R.

(Initialled) Ph.C.

65

Document file FR
Document Long Title

Judgment of 12 July 2005

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