INTERNATIONAL COURT OF JUSTICE

REPORTS OF JUDGMENTS,
ADVISORY OPINIONS AND ORDERS

CASE CONCERNING
KASIKILI/SEDUDU ISLAND

(BOTSWANA/NAMIBIA)

JUDGMENT OF 13 DECEMBER 1999

1999

COUR INTERNATIONALE DE JUSTICE

RECUEIL DES ARRETS,
AVIS CONSULTATIFS ET ORDONNANCES

AFFAIRE
DE L'ÎLE DE KASIKILI/SEDUDU

(BOTSWANA/NAMIBIE)

ARRET DU 13 DECEMBRE 1999
Official citation:

KasikililSedudu Island ( BotswanalNamibia),

Judgment, C.J. Reports 1999, p. 1045

Mode officiel de citation:

Ile de KasikililSedudu ( BotswanalNamibie ),
arrêt, C.LJ. Recueil 1999, p. 1045

Sales number
ISSN 0074-4441 N° de vente:

ISBN 92-1-070840-7

768

13 DECEMBER 1999

JUDGMENT

KASIKILI/SEDUDU ISLAND
(BOTSWANA/NAMIBIA)

ÎLE DE KASIKILI/SEDUDU
(BOTSWANA/NAMIBIE)

13 DECEMBRE 1999

ARRET
1999
13 December
General List
No. 98

1045

INTERNATIONAL COURT OF JUSTICE

YEAR 1999

13 December 1999

CASE CONCERNING
KASIKILI/SEDUDU ISLAND

(BOTSWANA/NAMIBIA)

Special Agreement.

Tasks of the Court — Determination of boundary around KasikililSedudu
Island — Determination of Island's legal status.

Applicable law — Anglo-German Treaty of 1890 — Rules and principles of
international law.

*  *

1890 Treaty — Rules of interpretation as expressed in the 1969 Vienna Con-
vention — Consideration of present-day scientific knowledge.

Text of Article I of the Treaty — Reference in English version to “centre of
the main channel”, in German version to “thalweg” of that channel — Various
definitions of the term “thalweg” — Equivalence of expressions “centre of the
main channel” and “Thalweg des Hauptlaufes” — Method to be employed for
interpretation of these expressions — Determination of “main channel” —
Ordinary meaning of words “main channel’ — Criteria enabling “main chan-
nel” to be identified — A number of criteria to be applied — depth; width; flow;
navigability — Questions of visibility (or general physical appearance) and of
the bed profile configuration of the channel.

Object and purpose of the 1890 Treaty.

Travaux préparatoires.

Subsequent practice of the parties to the Treaty and their successors —
Article 31, paragraph 3, of 1969 Vienna Convention — Eason Report (1912) —
Trollope-Redman correspondence (1947-1951) — Joint Survey of 1985 —
Presence of Masubia on the Island — Relevance of facts recorded, in absence of
subsequent practice.
1046 KASIKILI/SEDUDU ISLAND (JUDGMENT)

Maps — Evidentiary value — Map officially expressing intention of contract-
ing parties — Express or implied agreement on validity of a boundary depicted
on a map.

Location of boundary in the “main channel” — Term “thalweg” determina-
tive in Article III, paragraph 2, of the Treaty — Line of deepest soundings.

* *
Acquisitive prescription — Reference in Special Agreement to “rules and
principles of international law” — Basic conditions as set out by Namibia.
x Ox

Status of KasikililSedudu Island — Kasane Communiqué of 1992 — Mutual
guarantees for freedom of navigation.

JUDGMENT

Present: President SCHWEBEL; Vice-President WEERAMANTRY; Judges Oba,
BEDJAOUI, GUILLAUME, RANJEVA, HERCZEGH, SHI, FLEISCHHAUER,
KOROMA, VERESHCHETIN, HIGGINS, PARRA-ARANGUREN, KOOIIMANS,
Rezek; Registrar VALENCIA-OSPINA.

In the case concerning Kasikili/Sedudu Island,
between

the Republic of Botswana,
represented by

Mr. Abednego Batshani Tafa, Advocate of the High Court and Court of
Appeal of Botswana, Deputy Attorney-General,

as Agent, Counsel and Advocate;

HE. Mr. S. C. George, Ambassador of the Republic of Botswana to the
European Union, Brussels,

as Co-Agent;

Mr. Molosiwa L. Selepeng, Permanent Secretary for Political Affairs, Office
of the President,

Professor Ian Brownlie, C.B.E., Q.C., F.B.A., Chichele Professor of Public
International Law, University of Oxford, Member of the International
Law Commission, Member of the English Bar, Member of the Institut de
droit international,

Lady Fox Q.C., former Director of the British Institute of International and
Comparative Law, Member of the English Bar, Associate Member of the
Institut de droit international,

Dr. Stefan Talmon, Rechtsassessor, D.Phil. (Oxon), LL.M. (Cantab), Wissen-
schaftlicher Assistent in the Law Faculty of the University of Tubingen,

as Counsel and Advocates;
1047 KASIKILUSEDUDU ISLAND (JUDGMENT)

Mr. Timothy Daniel, Solicitor of the Supreme Court; Partner, D. J. Freeman
(Solicitors) of the City of London,

Mr. Alan Perry, Solicitor of the Supreme Court; Partner, D. J. Freeman
(Solicitors) of the City of London,

Mr. David Lerer, Solicitor of the Supreme Court; Assistant, D. J. Freeman
(Solicitors) of the City of London,

Mr. Christopher Hackford, Solicitor of the Supreme Court; Assistant, D. J.
Freeman (Solicitors) of the City of London,

Mr. Robert Paydon, Solicitor of the Supreme Court; Assistant, D. J. Free-
man (Solicitors) of the City of London,

as Counsel;

Professor F. T. K. Sefe, Professor of Hydrology, Department of Environ-
mental Science, University of Botswana, Gaborone,

Mr. Isaac Muzila, B.Sc. Civil Engineering, Principal Hydrological Engineer,
Department of Water Affairs, Botswana,

Mr. Alan Simpkins, F.R.1.C.S., Prof. M.LT.E.S. (S.A.), L.S. (Bots.), Chief
Surveyor and Deputy to Director, Department of Surveys and Mapping,
Botswana,

Mr. Scott B. Edmonds, Director of Cartographic Operations, GeoSystems
Global Corporation, Columbia, Maryland (United States of America),

Mr. Robert C. Rizzutti, Senior Mapping Specialist, GeoSystems Global Cor-
poration, Columbia, Maryland (United States of America),

Mr. Justin E. Morrill, Senior Multimedia Designer, GeoSystems Global Cor-
poration, Columbia, Maryland (United States of America),

as Scientific and Technical Advisers;

Mr. Bapasi Mphusu, Chief Press Officer, Department of Information and
Broadcasting, Government of Botswana,

as Information Adviser;
Mrs. Coralie Ayad, D. J. Freeman (Solicitors) of the City of London,

Mrs. Marilyn Beeson, D. J. Freeman (Solicitors) of the City of London,

Ms Michelle Burgoine, D. J. Freeman (Solicitors) of the City of London,

as Administrators,
and

the Republic of Namibia,

represented by:
Dr. Albert Kawana, Permanent Secretary, Ministry of Justice of Namibia,
as Agent, Counsel and Advocate;

H.E. Dr. Zedekia J. Ngavirue, Ambassador of the Republic of Namibia to
the Netherlands,

as Deputy-Agent;

Professor Abram Chayes, Felix Frankfurter Professor of Law Emeritus,
Harvard Law School,
1048 KASIKILI/SEDUDU ISLAND (JUDGMENT)

Sir Elihu Lauterpacht, C.B.E., Q.C., Honorary Professor of International
Law, University of Cambridge, Member of the Institut de droit interna-
tional,

Mr. Jean-Pierre Cot, Professor Emeritus, Université de Paris I (Panthéon-
Sorbonne), Member of the Paris and Brussels Bars, Vice-President of the
European Parliament,

Professor Dr. Jost Delbriick, Director of Walther-Schiicking Institute of
International Law, University of Kiel,

Professor Dr. Julio Faundez, Professor of Law, University of Warwick,

as Counsel and Advocates;

Professor W. J. R. Alexander, Emeritus Professor of Hydrology, University
of Pretoria,

Professor Keith S. Richards, Department of Geography, University of Cam-
bridge,

Colonel Dennis Rushworth, Former Director of the Mapping and Charting
Establishment, Ministry of Defence of the United Kingdom,

Dr. Lazarus Hangula, Director, Multidisciplinary Research Centre, Univer-
sity of Namibia,

as Advocates;

Dr. Arnold M. Mtopa, Chief Legal Officer, Ministry of Justice of Namibia,

Dr. Collins Parker, Chief Legal Officer, Ministry of Justice of Namibia,

Mr. Edward Helgeson, Fellow, Lauterpacht Research Centre for Interna-
tional Law, University of Cambridge,

Ms Tonya Putnam, Harvard Law School,

as Counsel and Advisers;

Mr. Peter Clark, Former Chief Map Research Officer, Ministry of Defence,
United Kingdom,

as Technical Adviser;

Mr. Samson N. Muhapi, Special Assistant to the Permanent Secretary,
Ministry of Justice of Namibia,

Ms Kyllikki M. Shaduka, Private Secretary, Ministry of Justice of Namibia,

Ms Mercia G. Louw, Private Secretary, Ministry of Justice of Namibia,

as administrative staff,

Mr. Peter Denk, Reporter,
Mr. Muyenga Muyenga, Reporter,

as Information Advisers,

THE Court,

composed as above,

after deliberation,

delivers the following Judgment:

1. By joint letter dated 17 May 1996, filed in the Registry of the Court on
29 May 1996, the Ministers for Foreign Affairs of the Republic of Botswana
(hereinafter called “Botswana”) and the Republic of Namibia (hereinafter
called “Namibia”) transmitted to the Registrar the original text of a Special

7
1049 KASIKILI/SEDUDU ISLAND (JUDGMENT)

Agreement between the two States, signed at Gaborone on 15 February 1996
and entered into force on 15 May 1996, the date of exchange of instruments of
ratification.

2. The text of the Special Agreement reads as follows:

“Whereas a Treaty between Great Britain and Germany respecting the
spheres of influence of the two countries in Africa was signed on 1 July
1890 (the Anglo-German Agreement of 1890);

Whereas a dispute exists between the Republic of Botswana and the
Republic of Namibia relative to the boundary around Kasikili/Sedudu
Island ;

Whereas the two countries are desirous of settling such dispute by
peaceful means in accordance with the principles of both the Charter of
the United Nations and the Charter of the Organization of African Unity;

Whereas the two countries appointed on 24 May 1992 a Joint Team of
Technical Experts on the Boundary between Botswana and Namibia
around Kasikili/Sedudu Island ‘to determine the boundary between
Namibia and Botswana around Kasikili/Sedudu Island’ on the basis of the
Treaty of 1 July 1890 between Great Britain and Germany respecting the
spheres of influence of the two countries in Africa and the applicable prin-
ciples of international law;

Whereas the Joint Team of Technical Experts was unable to reach a
conclusion on the question referred to it and recommended ‘recourse to
the peaceful settlement of the dispute on the basis of the applicable rules
and principles of international law’ ;

Whereas at the Summit Meeting held in Harare, Zimbabwe, on 15 Feb-
ruary 1995, and attended by Their Excellencies President Sir Ketumile
Masire of Botswana, President Sam Nujoma of Namibia and President
Robert Mugabe of Zimbabwe, the Heads of State of the Republic of Bot-
swana and the Republic of Namibia, acting on behalf of their respective
Governments, agreed to submit the dispute to the International Court of
Justice for a final and binding determination;

Now therefore the Republic of Botswana and the Republic of Namibia
have concluded the following Special Agreement:

Article I

The Court is asked to determine, on the basis of the Anglo-German
Treaty of 1 July 1890 and the rules and principles of international law, the
boundary between Namibia and Botswana around Kasikili/Sedudu Island
and the legal status of the island.

Article IT
1. The proceedings shall consist of written pleadings and oral hearings.

2. The written pleadings shall include:

(a) Memorials submitted to the Court by each Party not later than nine
months after the notification of the Special Agreement is transmitted
1050 KASIKILI/SEDUDU ISLAND (JUDGMENT)

to the Registrar of the Court in accordance with Article VII (2) of this
Special Agreement;
(b} Counter-Memorials submitted by each Party to the Court not later
than nine months after the date of submission of the Memorials;
{e) such other written pleadings as may be approved by the Court at the
request of either of the Parties, or as may be directed by the Court.

3. The written pleadings submitted to the Registrar shall not be com-
municated to the other Party until the corresponding pleadings of that
Party have been received by the Registrar.

Article Il

The rules and principles of international law applicable to the dispute
shall be those set forth in the provisions of Article 38, paragraph 1, of the
Statute of the International Court of Justice.

Article IV

The order of appearance in the oral pleadings shall be as agreed by the
Parties with the approval of the Court, or in the absence of agreement, as
directed by the Court.

Article V

The order of the written pleadings and oral submissions shall be without
prejudice to the burden of proof.

Article VI
The language of the proceedings shall be English.
Article VII

1. This agreement shall enter into force on the date of the exchange of
instruments of ratification by the two Governments.

2. It shall be notified to the Court as required by Article 40, para-
graph 3, of the Statute of the Court by joint letter of the Parties to the
Registrar.

3. If such notification is not effected within two months from the entry
into force of this Special Agreement, it may be notified to the Registrar by
either of the Parties.

Article VHT

1. Each of the Parties may exercise its right under Article 31, para-
graph 3, of the Statute of the Court to choose a person to sit as judge.

2. A Party which chooses to exercise the right referred to in sub-
Article 1, above, shall notify the other Party in writing prior to exercising
such right.

Article 1X

1. The judgment of the Court on the dispute described in Article I shall
be final and binding on the Parties.

2. As soon as possible after the delivery of the Court’s judgment, the
Parties shall take steps necessary to carry out the judgment.
1051 KASIKILI/SEDUDU ISLAND (JUDGMENT)

In witness whereof, the undersigned, being duly authorized thereto, have
signed this Special Agreement and have affixed thereto their seals.”

3. Pursuant to Article 40, paragraph 3, of the Statute and Article 42 of the
Rules of Court, copies of the notification and of the Special Agreement were
transmitted by the Registrar to the Secretary-General of the United Nations,
the Members of the United Nations and other States entitled to appear before
the Court.

4. By Order of 24 June 1996, the Court fixed 28 February 1997 as the time-
limit for the filing of a Memorial by each Party and 28 November 1997 as the
time-limit for the filing by each Party of a Counter-Memorial, having regard to
the provisions of Article I], paragraph 2 (a) and (b), of the Special Agree-
ment. These pleadings were duly filed within the time-limits so prescribed.

5. By Order of 27 February 1998, the Court fixed 27 November 1998 as the
time-limit for the filing of a Reply by each Party, having regard to the provi-
sions of Article I], paragraph 2 (c), of the Special Agreement and taking
account of the agreement between the Parties, as expressed in a joint letter from
their Agents dated 16 February 1998. The Replies were duly filed within the
time-limit so prescribed. As the Parties did not request the submission of other
pleadings, and as the Court itself did not consider this necessary, the case was
then ready for hearing.

6. In accordance with Article 53, paragraph 2, of the Rules of Court, the
Court decided, after having ascertained the views of the Parties, that copies of
the pleadings and documents annexed would be made available to the public as
from the opening of the oral proceedings.

7. New documents were produced by each of the Parties, with the consent of
the other, in accordance with Article 56, paragraph 1, of the Rules of Court. In
addition, Namibia, availing itself of the right provided for in Article 56, para-
graph 3, of the Rules of Court, submitted comments on certain of the new
documents produced by Botswana.

8. The Parties having been duly consulted, in accordance with Article 58,
paragraph 2, of the Rules of Court, and having informed the Court of their
agreement, in accordance with Article IV of the Special Agreement, on the order
of speaking, public sittings were held between 15 February and 5 March
1999, during which oral arguments and replies were heard from the following:

For Namibia: Dr. Albert Kawana,
Professor Abram Chayes,
Professor Dr. Jost Delbriick,
Professor W. J. R. Alexander,
Dr. Lazarus Hangula,
Professor Dr. Julio Faundez,
Colonel Dennis Rushworth,
Mr. Jean-Pierre Cot.

For Botswana: Mr. Abednego Batshani Tafa,
Mr. Molosiwa L. Selepeng,
Professor Ian Brownlie,
Lady Fox,
Dr. Stefan Talmon,
Professor F. T. K. Sefe,
Mr. Isaac Muzila.

10
1052 KASIKILI/SEDUDU ISLAND (JUDGMENT)

At the sittings, each of the Parties showed a video cassette, after those
cassettes had been exchanged between the Parties through the intermediary of
the Registry.

Questions were also put by Members of the Court, to which both Parties
replied in writing, within the time-limit fixed for this purpose.

2

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

On behalf of Botswana,
in the Memorial, the Counter-Memorial and the Reply:

“May it please the Court to adjudge and declare that:

1. The northern and western channel of the Chobe River in the vicinity of
Kasikili/Sedudu Island constitutes the ‘main channel’ of the Chobe
River in accordance with the provisions of Article III (2) of the Anglo-
German Agreement of 1890; and that:

2. Consequently, sovereignty in respect of Kasikili/Sedudu Island inheres
exclusively in the Republic of Botswana.”

On behalf of Namibia,
in the Memorial and the Counter-Memorial:

“May it please the Court, rejecting all claims and submissions to the con-
trary, to adjudge and declare:

1. The channel that lies to the south of Kasikili/Sedudu Island is the main
channel of the Chobe River.

2. The channel that lies to the north of Kasikili/Sedudu Island is not the
main channel of the Chobe River.

3. Namibia and its predecessors have occupied and used Kasikili Island
and exercised sovereign jurisdiction over it, with the knowledge and
acquiescence of Botswana and its predecessors since at least 1890.

4, The boundary between Namibia and Botswana around Kasikili/Sedudu
Island lies in the centre of the southern channel of the Chobe River.

5. The legal status of Kasikili/Sedudu Island is that it is a part of the ter-
ritory under the sovereignty of Namibia.”

in the Reply:

“May it please the Court, rejecting all claims and submissions to the con-
trary, to adjudge and declare

1. The channel that lies to the south of Kasikili/Sedudu Island is the main
channel of the Chobe River.

2. The channel that lies to the north of Kasikili/Sedudu Island is not the
main channel of the Chobe River.

3. Namibia and its predecessors have occupied and used Kasikili Island
and exercised sovereign jurisdiction over it, with the knowledge and
acquiescence of Botswana and its predecessors since at least 1890.

4. The boundary between Namibia and Botswana around Kasikili/Sedudu
Island lies in the centre (that is to say, the thalweg) of the southern
channel of the Chobe River.
1053 KASIKILI/SEDUDU ISLAND (JUDGMENT)

5. The legal status of Kasikili/Sedudu Island is that it is a part of the ter-
ritory under the sovereignty of Namibia.”

10. In the oral proceedings, the following submissions were presented by the
Parties:

On behalf of Botswana,
at the hearing of 5 March 1999:
“May it please the Court:
(1) to adjudge and declare:
(a) that the northern and western channel of the Chobe River in the
vicinity of Kasikili/Sedudu Island constitutes the ‘main channel’ of
the Chobe River in accordance with the provisions of Article III (2)
of the Anglo-German Agreement of 1890; and
(6) consequently, sovereignty in respect of Kasikili/Sedudu Island vests
exclusively in the Republic of Botswana; and further
(2) to determine the boundary around Kasikili/Sedudu Island on the

basis of the thalweg in the northern and western channel of the
Chobe River.”

On behalf of Namibia,
at the hearing of 2 March 1999:

The submissions read at the hearing were identical to those presented by

Namibia in the Reply.
x * x

11. The Parties, in the terms of the Special Agreement, request the
Court, “to determine, on the basis of the Anglo-German Treaty of | July
1890 and the rules and principles of international law, the boundary
between Namibia and Botswana around Kasikili/Sedudu Island and the
legal status of the island.” The Island referred to, which in Namibia
is known as “Kasikili”, and in Botswana as “Sedudu”, is approximately
3.5 square kilometres (1.5 square miles) in area. It is located in the
Chobe River, which divides around it to the north and south, in the
area bounded approximately by meridians 25° 07’ and 25° 08’ E longitude
and parallels 17°47’ and 17°50’ S latitude, and is some 20 kilometres
(12.5 miles) upstream of Kazungula where the Chobe flows into the Zam-
bezi. The Chobe has its source on the central plateau of Angola, where it is
called the Rio Cuando. It undergoes further changes of name at various
stages along its course. When it crosses the border into Namibia, it
becomes the Kwando and then the Mashi, which flows generally in a
southerly direction into the Linyanti (or Linyandi) Swamp. From this
point it is called the Linyanti (or Linyandi) River until it reaches Lake
Liambezi. At the exit from the lake, the river becomes the Chobe. The
Botswana town of Kasane lies on the south bank some 1.5 kilometres
downstream from Kasikili/Sedudu Island, and the Namibian village of
Kasika is located on the northwestern bank of the Chobe.

12. Nearly due south of the Island, on the Botswana side, are the

12
1054 KASIKILI/SEDUDU ISLAND (JUDGMENT)

headquarters of the Chobe National Park, a protected reserve with a
wide variety of wildlife. This southern bank is characterized by a steep
sandy ridge ranging between 900 and 1,000 metres above mean sea level.
The area on the Namibian side, to the north of the Island, has no such
geographical feature. It forms part of a strip of territory called the
“Caprivi Strip”, after the German chancellor at the time of the conclu-
sion of the Anglo-German Agreement of | July 1890 (hereinafter the
“1890 Treaty”). This part of the Caprivi Strip is within the seasonal flood
plain of the Zambezi River. The Island, which is 927 metres above mean
sea level, forms part of this plain, and is subject to flooding of several
months’ duration, beginning around March. In order to assist in the
reading of this Judgment, the Court has included below three sketch-
maps, the first illustrating the position of Botswana and Namibia on the
continent of Africa (Sketch-map No. |, page 1055); the second showing
the Caprivi Strip and the Chobe (Sketch-map No. 2, page 1056); and the
third showing Kasikili/Sedudu Island (Sketch-map No. 3, page 1057).

13. The dispute between the Parties is set against the background of
the nineteenth century race among the European colonial powers for the
partition of Africa. In the spring of 1890, Germany and Great Britain
entered into negotiations with a view to reaching agreement concerning
their trade and their spheres of influence in Africa. In the south-west of
the continent, Great Britain sought to protect the south-north trade
routes running through Lake Ngami to Victoria Falls, while Germany,
which had already laid claim to a large portion of what was called “South
West Africa”, sought British recognition of its access to the Zambezi.
These negotiations culminated in the conclusion of the 1890 Treaty,
which concerned several regions of the African continent, namely east
Africa, south-west Africa, Togo and Zanzibar, and involved the cession
to Germany of the island of Heligoland, in exchange for Zanzibar. The
Treaty delimited inter alia the spheres of influence of Germany and Great
Britain in south-west Africa; that delimitation lies at the heart of the
present case.

14. In the ensuing century, the territories involved experienced various
mutations in status. The independent Republic of Botswana came into
being on 30 September 1966, on the territory of the former British
Bechuanaland Protectorate. German administration of South West Africa
turned out to be short-lived. Upon the outbreak of the First World War
in 1914, the Caprivi Strip was occupied and governed by British forces
from Southern Rhodesia. From 1919 until 1966, South Africa was the
administering authority of the territory of South West Africa under a
mandate from the League of Nations. For part of this period, from 1921
to 1929, South Africa delegated the administration of the Caprivi Strip to
the authorities of the British Bechuanaland Protectorate. South Africa’s
mandate over South West Africa was terminated by the United Nations
General Assembly in 1966, following which the Assembly established a

13

AFRICA

Caprivi Strip

Botswana

SKETCH-MAP No. 1

Botswana and Namibia

N.B.: This sketch-map has
been prepared by the Court
for illustrative purposes only

Sketch-map not to scale

ZAMBIA

ANGOLA

NAMIBIA

/ ~ A,
/ ™
/
. . . D /
(Caprivi Strip) S/
Northern Channel /
Kasika (Namibia) De fq Kasane (Botswana)
e / NO
/ Si
et /
f Kasikili / /
/ { Sedudu
_--~ / Island
“a f #
Spur Channel J 1, Southern Channel
re PA Ar 7 |
a
cnt
a
BOTSWANA

SKETCH-MAP No. 3

Kasikili / Sedudu Island

N.B.: This sketch-map has
been prepared by the Court
for illustrative purposes only

Sketch-map not to scale

1058 KASIKILI/SEDUDU ISLAND (JUDGMENT)

United Nations Council for South West Africa (which subsequently
became the United Nations Council for Namibia), which it designated as
the authority responsible for the administration of Namibia; but South
Africa remained in de facto control of the territory, despite United
Nations policy to the contrary, until Namibia’s independence on
21 March 1990.

15. Shortly after Namibian independence, differences arose between
the two States concerning the location of the boundary around Kasikili/
Sedudu Island. When the two Parties proved unable to resolve their dis-
pute, they called upon the good offices of the President of Zimbabwe. His
efforts led to a meeting of the Presidents of the three countries at Kasane,
Botswana, in May 1992, at which they issued a communiqué, declaring
that the issue should be resolved peacefully, and recording the Presidents’
agreement to submit the determination of the boundary around Kasikili/
Sedudu Island to a Joint Team of Technical Experts. Terms of reference
for the Joint Team were agreed between the parties in December 1992,
and the Joint Team conducted its survey between September 1993
and August 1994. In its final Report, issued on 20 August 1994, the Joint
Team announced that it had failed to reach an agreed conclusion on the
question put to it, and recommended recourse to the peaceful settlement
of the dispute on the basis of the applicable rules and principles of inter-
national law.

16. In February 1995, the three Presidents met in Harare, Zimbabwe,
to consider the Joint Team Report. At this meeting, it was decided to
submit the dispute to the International Court of Justice for a final and
binding determination. Pursuant to this decision, Botswana and Namibia,
by a Special Agreement signed at Gaborone on 15 February 1996,
brought the dispute before the Court.

x * +

17. The Court recalls that according to Article I of the Special Agree-
ment, it:

“is asked to determine, on the basis of the Anglo-German Treaty of
1 July 1890 and the rules and principles of international law, the
boundary between Namibia and Botswana around Kasikili/Sedudu
Island and the legal status of the island”.

Accordingly the Court has a dual task: to determine both the boundary
between Botswana and Namibia around Kasikili/Sedudu Island and the
legal status of the Island. For this purpose, the Court must base itself on
the 1890 Treaty and on the rules and principles of international law.

a
1059 KASIKILI/SEDUDU ISLAND (JUDGMENT)

18. The law applicable to the present case has its source first of all in
the 1890 Treaty, which Botswana and Namibia acknowledge to be bind-
ing on them.

As regards the interpretation of that Treaty, the Court notes that
neither Botswana nor Namibia are parties to the Vienna Convention on
the Law of Treaties of 23 May 1969, but that both of them consider that
Article 31 of the Vienna Convention is applicable inasmuch as it reflects
customary international law. The Court itself has already had occasion in
the past to hold that customary international law found expression in
Article 31 of the Vienna Convention (see Territorial Dispute (Libyan
Arab JamahiriyalChad), Judgment, 1 C.J. Reports 1994, p. 21, para. 41;
Oil Platforms (Islamic Republic of Iran v. United States of America),
Preliminary Objections, Judgment, ..C.J. Reports 1996 (11), p. 812,
para. 23). Article 4 of the Convention, which provides that it “applies
only to treaties which are concluded by States after the entry into force of
the . . . Convention with regard to such States” does not, therefore,
prevent the Court from interpreting the 1890 Treaty in accordance with
the rules reflected in Article 31 of the Convention.

According to Article 31 of the Vienna Convention on the Law of
Treaties:

“1, A treaty shall be interpreted in good faith in accordance with
the ordinary meaning to be given to the terms of the treaty in their
context and in the light of its object and purpose.

2. The context for the purpose of the interpretation of a treaty shall
comprise, in addition to the text, including its preamble and annexes:

(a) any agreement relating to the treaty which was made between
all the parties in connection with the conclusion of the treaty;

(6) any instrument which was made by one or more parties in con-
nection with the conclusion of the treaty and accepted by the
other parties as an instrument related to the treaty.”

19. The Special Agreement also refers, in Article 1, to the “rules and
principles of international law”. Article III] of the Special Agreement
further states that these rules and principles “shall be those set forth in
the provisions of Article 38, paragraph 1, of the Statute of the Interna-
tional Court of Justice”. The Court will revert to the issue — in dispute
between the parties — of whether this reference in the Special Agreement
to the “rules and principles of international law” permits the Court to
entertain Namibia’s alternative argument founded on the doctrine of pre-
scription (see paragraphs 90-94 below).

The Parties also refer to the principles of both the Charter of the
United Nations and the Charter of the Organization of African Unity
(OAU), as well as to resolution AHG/Res. 16 (1), adopted in Cairo on
21 July 1964 by the Assembly of Heads of State and Government of the
OAU. The latter provides that Member States of the OAU pledge them-
selves inter alia to respect the frontiers existing on their achievement

18
1060 KASIKILI/SEDUDU ISLAND (JUDGMENT)

of national independence (an implementation of the principle of uti
possedetis juris).

+ * x

20. The Court will now proceed to interpret the provisions of the 1890
Treaty by applying the rules of interpretation set forth in the 1969 Vienna
Convention. It recalls that

“a treaty must be interpreted in good faith, in accordance with the
ordinary meaning to be given to its terms in their context and in the
light of its object and purpose. Interpretation must be based above
all upon the text of the treaty. As a supplementary measure recourse
may be had to means of interpretation such as the preparatory work
of the treaty.” (Territorial Dispute (Libyan Arab JamahiriyalChad),
Judgment, 1 C.J. Reports 1994, pp. 21-22, para. 41.)

In order to illuminate the meaning of words agreed upon in 1890, there
is nothing that prevents the Court from taking into account the present-
day state of scientific knowledge, as reflected in the documentary material
submitted to it by the Parties (compare Controversia sobre el recorrido de
la traza del limite entre el Hito 62 y el Monte Fitz Roy ( ArgentinalChile)
[Dispute concerning the course of the frontier between B.P. 62 and
Mount Fitzroy (ArgentinalChile)], also known as the “Laguna del
desierto” case, Arbitral Award of 21 October 1994, International Law
Reports (ILR), Vol. 113, p. 76, para. 157; Revue générale de droit inter-
national public (RGDIP), Vol. 2, 1996, p. 592, para. 157).

21. The Court will first examine the text of the 1890 Treaty, Article III
of which reads as follows:

“In Southwest Africa the sphere in which the exercise of influence
is reserved to Germany is bounded:

1. To the south by a line commencing at the mouth of the Orange
river, and ascending the north bank of that river to the point of its
intersection by the 20th degree of east longitude.

2. To the east by a line commencing at the above-named point,
and following the 20th degree of east longitude to the point of its
intersection by the 22nd parallel of south latitude; it runs eastward
along that parallel to the point of its intersection by the 21st degree
of east longitude; thence it follows that degree northward to the
point of its intersection by the 18th parallel of south latitude; it runs
eastward along that parallel till it reaches the river Chobe, and
descends the centre of the main channel of that river to its junction
with the Zambesi, where it terminates.

It is understood that under this arrangement Germany shall have
free access from her Protectorate to the Zambesi by a strip of terri-
tory which shall at no point be less than 20 English miles in width.

19
1061 KASIKILI/SEDUDU ISLAND (JUDGMENT)

The sphere in which the exercise of influence is reserved to Great
Britain is bounded to the west and northwest by the above-
mentioned line. It includes Lake Ngami.

The course of the above boundary is traced in general accordance
with a map officially prepared for the British Government in 1889.”

As far as the region covered by the present case is concerned, this pro-
vision locates the dividing line between the spheres of influence of the
contracting parties in the “main channel” of the River Chobe; however,
neither this, nor any other provision of the Treaty, furnishes criteria
enabling that “main channel” to be identified. It must also be noted that
the English version refers to the “centre” of the main channel, while the
German version uses the term “thalweg” of that channel (Thalweg
des Hauptlaufes).

22. Throughout the proceedings, the Parties have expressed differing
opinions regarding the method to be applied for the purpose of interpret-
ing these expressions. Botswana contends that:

“[in a bifurcated stretch of river, such as the Chobe River in the
vicinity of Kasikili/Sedudu Island, both channels will have their
respective thalwege. However, the thalweg of the main channel will
be at a lower elevation than the thalweg of the other channel. Only
the thalweg of the main channel can be logically connected to the
thalweg of the channel upstream of the point of bifurcation and
downstream of the point of reunion.”

Botswana maintains that, in order to establish the line of the boundary
around Kasikili/Sedudu Island, it is sufficient to determine the thalweg of
the Chobe; it is that which identifies the main channel of the river. For
Botswana, the words “des Hauptlaufes” therefore add nothing to the
text.

23. For Namibia, however, the task of the Court is first to identify the
main channel of the Chobe around Kasikili/Sedudu Island, and then to
determine where the centre of this channel lies:

“The ‘main channel’ must be found first; the ‘centre’ can neces-
sarily only be found afterward. This point is equally pertinent to the
German translation of the formula‘. . . im Thalweg des Hauptlaufes
... In the same way as with the English text, the search must first be
for the ‘Hauptlauf and for the ‘Thalweg’ only after the ‘Hauptlauf
has been found. The ‘Hauptlauf cannot be identified by first seeking
to find the ‘Thalweg’.”

24. The Court notes that various definitions of the term “thalweg” are
found in treaties delimiting boundaries and that the concepts of the thal-
weg of a watercourse and the centre of a watercourse are not equivalent.
The word “thalweg” has variously been taken to mean “the most suitable
channel for navigation” on the river, the line “determined by the line of

20
1062 KASIKILI/SEDUDU ISLAND (JUDGMENT)

deepest soundings”, or “the median line of the main channel followed by
boatmen travelling downstream”. 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.

25. The Court further notes that at the time of the conclusion of the
1890 Treaty, it may be that the terms “centre of the [main] channel” and
“Thalweg”des Hauptlaufes were used interchangeably. In this respect, it
is of interest to note that, some three years before the conclusion of the
1890 Treaty, the Institut de droit international stated the following in
Article 3, paragraph 2, of the “Draft concerning the international regula-
tion of fluvial navigation”, adopted at Heidelberg on 9 September 1887:
“The boundary of States separated by a river is indicated by the thalweg,
that is to say, the median line of the channel” (Annuaire de l'Institut de
droit international, 1887-1888, p. 182), the term “channel” being under-
stood to refer to the passage open to navigation in the bed of the river,
as is clear from the title of the draft. Indeed, the parties to the 1890
Treaty themselves used the terms “centre of the channel” and “thalweg”
as synonyms, one being understood as the translation of the other
(see paragraph 46 below).

The Court observes, moreover, that in the course of the proceedings,
Botswana and Namibia did not themselves express any real difference
of opinion on this subject. The Court will accordingly treat the words
“centre of the main channel” in Article III, paragraph 2, of the 1890
Treaty as having the same meaning as the words “Thalweg des Haupt-
laufes” (cf. 1969 Vienna Convention on the Law of Treaties, Article 33,
paragraph 3, under which “the terms of the treaty are presumed to
have the same meaning in each authentic text”).

26. The Court adds that, in this case, the Parties to the dispute have
used the term “channel” to refer to each of the two branches of the
Chobe that ring Kasikili/Sedudu Island, and have not confined the term
“channel” to the stricter usage meaning the navigable passage of a river
or of one of its branches. In view of this fact, the Court itself in this Judg-
ment will likewise employ the term “channel” in a broad sense.

27. In the Court’s opinion, the real dispute between the Parties con-
cerns the location of the main channel where the boundary lies. In Bot-
swana’s view, it is to be found “on the basis of the thalwegs in the
northern and western channel of the Chobe”, whereas in Namibia’s view,
it “lies in the centre (that is to say thalweg) of the southern channel of the
Chobe River”.

While Botswana thought it sufficient for the Court to locate the line of
deepest soundings in this section of the Chobe, which in its view leads to
the centre of the northern channel as the boundary, the Court notes that
this was not the only test it relied on. Moreover, the Court observes that
by introducing the term “main channel” into the draft treaty, the con-

21
1063 KASIKILI/SEDUDU ISLAND (JUDGMENT)

tracting parties must be assumed to have intended that a precise meaning
be given to it. For these reasons, the Court will therefore proceed first to
determine the main channel. In so doing, it will seek to determine the
ordinary meaning of the words “main channel” by reference to the most
commonly used criteria in international law and practice, to which the
Parties have referred.

* x

28. Before entering into an examination of these criteria, the Court
observes that the Parties’ experts have submitted to it extensive, often
contradictory, information on the distinguishing features of the Chobe.

For Botswana, the Chobe “is a perennial river independent of the
Zambezi River, with a stable profile, continuous downstream flow and
visible and stable banks”.

Namibia, for its part, claims that the Chobe cannot be regarded as a
perennial river, and that in reality it is an ephemeral watercourse. Namibia
points out that the Chobe is very often dry over a substantial section of
its course, so that it is not navigable over most of its length.

The Court does not find itself charged with making findings on the dis-
tinguishing features of the Chobe River. It will take these into account
only in so far as they affect the sector of Kasikili/Sedudu Island. The
Court’s task is in fact limited to settling the dispute between Botswana
and Namibia by determining the boundary between these two States
around the Island as well as the legal status of the Island.

29. The Parties to the dispute agree on many of the criteria for iden-
tifying the “main channel”, but disagree on the relevance and applica-
bility of several of those criteria.

For Botswana, the relevant criteria are as follows: greatest depth and
width; bed profile configuration; navigability; greater flow of water. Bot-
swana also lays stress, in the following terms, on the importance, from the
standpoint of identification of the main channel, of “channel capacity”,
“flow velocity”and “volume of flow”:

“channel capacity — This is determined by width and depth of the
channel and in the discharge equation it is represented by cross-
sectional area. From the cross-section survey and the analysis of
satellite imagery, it is clear that the northern channel is deeper
than the southern channel... .

flow velocity — Flow velocity is a function of bed slope, hydraulic
radius and roughness coefficient. . . . the northern channel has a
steeper bed slope; both of its banks are smooth (compared to the
southern channel), therefore velocity will be higher in that channel.

volume of flow — Volume of flow in a channel is computed as the

22
1064 KASIKILI/SEDUDU ISLAND (JUDGMENT)

product of channel capacity (cross-section area) and mean velocity
through the cross-section.”

Namibia acknowledges that

“[plossible criteria for identifying the main channel in a river with
more than one channel are the channel with the greatest width, or
the greatest depth, or the channel that carries the largest proportion
of the annual flow of the river. In many cases the main channel will
have all three of these characteristics.”

It adds, however, referring to the sharp variations in the level of the
Chobe’s waters, that: “neither width nor depth are suitable criteria for
determining which channel is the main channel.” Namibia nevertheless
further states the following:

“Various criteria may be employed; these include width, depth,
velocity, discharge, and sediment transport capacity. Since discharge
is the product of width, mean depth and mean velocity, and is a
determinant of transport capacity, it is the most straightforward and
general criterion.”

Among the possible criteria, Namibia therefore attaches the greatest
weight to the amount of flow: according to Namibia, the main channel is
the one “that carries the largest proportion of the annual flow of the
river”. Namibia also emphasized that another key task was to identify
the channel that is “most used for river traffic”.

30. The Court finds that it cannot rely on one single criterion in order
to identify the main channel of the Chobe around Kasikili/Sedudu Island,
because the natural features of a river may vary markedly along its
course and from one case to another. The scientific works which define
the concept of “main channel” frequently refer to various criteria: thus,
in the Dictionnaire francais d’hydrologie de surface avec équivalents en
anglais, espagnol, allemand (Masson, 1986), the “main channel” is “the
widest, deepest channel, in particular the one which carries the greatest
flow of water” (p. 66); according to the Water and Wastewater Control
Engineering Glossary (Joint Editorial Board Representing the American
Public Health Association, American Society of Civil Engineers, Ameri-
can Water Works Association and Water Pollution Control Federation,
1969), the “main channel” is “the middle, deepest or most navigable
channel” (p. 197). Similarly, in the Rio Palena Arbitration, the arbitral
tribunal appointed by the Queen of England applied several criteria in
determining the major channel of a boundary river (Argentina-Chile
Frontier Case (1966), United Nations, Reports of International Arbitral
Awards (RIAA), Vol. XVI, pp. 177-180; International Law Reports
(ILR), Vol. 38, pp. 94-98). The Court notes that the Parties have
expressed their views on one or another aspect of the criteria mentioned
in paragraph 29 above, distinguishing between them or placing emphasis

23
1065 KASIKILI/SEDUDU ISLAND (JUDGMENT)

on their complementarity and their relationship with other criteria. It will
take into account all of these criteria.

31. Before coming to a conclusion on the respective role and signifi-
cance of the various criteria thus chosen, the Court notes, on the basis of
the information supplied by both Parties concerning the hydrological
situation of Kasikili/Sedudu Island, that there are compelling reasons for
assuming that this situation has seen no radical change over the last hun-
dred years. The aerial photographs taken in 1925, 1943, 1947, 1962, 1972,
1977, 1981 and 1985 show no major mutation in the channels of the
Chobe and indicate that the channels surrounding the Island remained
relatively stable throughout that period of time. Moreover, the Parties
are in agreement on this point. Namibia states on this count:

“Namibia’s position does not depend on any changes in the gen-
eral configuration of the Island and the surrounding area since the
Treaty was signed. Thus, Namibia accepts that there have been no
significant changes in the location of the northern and southern
channels since 1890.”

Similarly, Botswana affirms that there

“is a complete absence of any evidence of radical change in the
course of the Chobe. Large scale maps both before and after the
1890 Anglo-German Agreement, prepared by those who had actu-
ally surveyed this stretch of the Chobe River, show an unchanged
course.”

In short, the present hydrological situation of the Chobe around
Kasikili/Sedudu Island may be presumed to be essentially the same as
that which existed when the 1890 Treaty was concluded.

32. The Court will first examine the criterion of depth. According to
Botswana’s experts, the mean depth of the northern channel is
5.70 metres, clearly exceeding the mean depth of the southern channel by
2.13 metres. As for the shallowest points, the depth is said to be 1.5 to
2 metres at the entry to the southern channel, i.e., a much shallower
depth than in the northern channel.

Although Namibia agrees that the northern channel has the greater
mean depth, it disputes that this conclusion is of any importance what-
soever for determining the main channel. It maintains that what is impor-
tant in this respect is not mean depth but draught at the shallowest point
of the channel; and it asserts that any differences between the shallowest
points in the northern and southern channels are minute. For Namibia,
the results of the 1985 Joint Survey (see paragraph 64 below) in respect of
the minimum depth of the two channels (see Reply of Namibia, Vol. II,
Second supplementary report to the expert report on the identification of
the main channel of the Chobe River at Kasikili Island, Fig. 14) are incon-

24
1066 KASIKILI/SEDUDU ISLAND (JUDGMENT)

clusive, in so far as “the minimum thalweg depths of the two channels
within the bifurcation zone were not determined” Namibia also intro-
duced photographs showing a herd of elephants crossing the two chan-
nels of the Chobe, but produced no figures to show that the minimum
depth of the southern channel was greater than that of the northern
channel.

Notwithstanding all the difficulties involved in sounding the depth of
the channels and interpreting the results, the Court concludes that the
northern channel is deeper than the southern one as regards mean depth,
and even as regards minimum depth.

33. The Court will now consider the criterion of width. The width of a
river may increase or decrease in line with the variable level of its waters.
In order to deal with this phenomenon, the width has often been deter-
mined on the basis of the low water mark (see, e.g., Article IX of the
Boundary Convention between Baden and France of 30 January 1827
(De Clerq, Recueil des Traités de la France, Vol. Ill, pp. 429 et seq.); see
also the judgment of the United States Supreme Court of 19 May 1933 in
the case Vermont v. New Hampshire, United States Reports, Vol. 289,
p. 619 (1933)) or the mean water level (see, e.g., the Arbitral Award ren-
dered on 23 January 1933 by the Special Boundary Tribunal constituted
by the Treaty of Arbitration between Guatemala and Honduras (League
of Nations Treaty Series, Vol. 137, p. 259; United Nations Reports of
International Arbitral Awards( RIAA), Vol. IL, p. 1365)), which offer an
acceptable basis for defining the characteristic features of a watercourse
(channels, centre, flow, etc.).

As early as 1912, Captain Eason, of the Bechuanaland Police, after
having visited the area, described the northern channel as being twice the
width of the southern channel (see paragraph 53 below). The aerial
photographs of the area concerned taken between 1925 and 1985 show
a northern channel that is wider than the southern one. The satellite pic-
tures taken in June 1975, then in March 1995 and June 1996 — Le., in
both the dry and rainy seasons — show the northern channel as being
wider than the southern channel. The Court concludes that apart from
the season of flooding that is indeed the situation.

34. The Parties both agree that the flow, i.e., the volume of water
carried, plays an important role, and for Namibia even a decisive role,
in determining the main channel — although they do not reach the
same conclusion.

According to the data submitted by Botswana,

“the northern channel conveys about twice as much flow as the
southern channel. The mean discharge at Site I] in the northern
channel is 78.865 m/s compared to 41.823 m*/s at Site I in the
southern channel. . .. Notice that the ratio of roughly 1:2 between

25
1067 KASIKILI/SEDUDU ISLAND (JUDGMENT)

the mean discharges of the southern and northern channels also
applies to the median and maximum discharges.”

Namibia criticizes this choice of gauging points, as well as the methods
used, and disputes the accuracy of the figures provided by Botswana. For
its part, it contends that

“the southern channel carries not only the major portion, but sub-
stantially all of the flow of the River in the vicinity of Kasikili
Island, while the northern channel has almost no longitudinal flow
and is little more than a relict channel of the Zambezi floodplain”.

Namibia provides the following figures for the volume of flow during
the period from 30 April to 2 May 1998:

“In the main channel to the south of the Island, the flow was
247 m/s, i.e., almost 60% of the total. In the northern channel it was
188 m°/s.”

35. The Court is not in a position to reconcile the figures submitted by
the Parties, who take a totally different approach to the definition of the
channels concerned. In Botswana’s presentation, the two channels around
Kasikili/Sedudu Island are those visible on the map (reproduced on
page 1068 of this Judgment). For its part, Namibia argues, placing particu-
lar reliance on certain maps and images, in support of the existence of a
major channel of the Chobe, of which the southern channel — visible
throughout the year except when the river is in flood — merely consti-
tutes the thalweg (see the aerial photograph reproduced on page 1069 of
this Judgment). According to Namibia, “the left bank [of this large chan-
nel] is marked by the line of high ground crossing the Island in a west-
east direction”. This is the channel said to carry “the largest proportion
of the annual flow of the river” and therefore to constitute the main
channel of the Chobe in the sector of Kasikili/Sedudu Island. On a
number of the photographs and maps submitted by Namibia (including
the photograph reproduced on page 1069 of this Judgment), the banks of
this channel, described as the main channel, are shown by means of
arrows or by a continuous line.

36. Botswana vigorously disputes the existence of this channel. It
states the following:

“[Firstly], the surmised Namibian waterway across the Island
occupies one sixth to one fifth of the northern channel. Secondly, it
traverses the high elevations of the Island. Thirdly, the proposed line
of its left bank, on examination of the aerial photographs and
satellite images, is not a bank but a narrow sub-channel. Fourthly,
that line is not tree-lined; and fifthly, the lower eastern areas of
the Island, on the evidence, are the more probable path of overflow
of Zambezi floods.”

26
1068 KASIKILI/SEDUDU ISLAND (JUDGMENT)

Map SHOWING THE Two CHANNELS AROUND KASIKILI/SEDUDU ISLAND
ACCORDING TO BOTSWANA

(Source : Botswana Judges’ Folder — Section 4)

28°

Kasane
Forest
Reserve

Island

€

+

Ch
National Park

BOTS W ANA

Headquarters

AS’ Sedudu

No1.4

Emerging sediment bars after the
passage of the seasonal flow in the river

NOTE: The flow in the Chobe River at Kasikill Island is seasonal, with no flow taking place in the dry season.
During the dry season the water in the northern and southern channels is stagnant. During the wet season
as flow commences the sediment bars in the main channel become inundated and flow takes place
through the full width of the main channel. After the passage of the annual flow the water level drops,
the sediment bars emerge, the flow ceases, and the water within the northem and southem channels
becomes stagnant once more.

Inflow into the northern channel directly from
the Zambezi River has already ceased

Figure 18
The location of the main channel
of the Chobe River at Kasikili Island.

Date of photography 5 June 1997

(p'] ‘ON JusUND0q — 1PIOA .sospne PIQIUIEN : aaunog)

VISINVN OL ONIGYODOV
CNV'IS] AGAGAS/TIDHISVYH GNNOUV STANNVHD OM], SHL ONIMOHS HdV490LOHdq
1070 KASIKILI/SEDUDU ISLAND (JUDGMENT)

In short, Botswana states, there is

“no independent evidence to support the existence of a ‘channel’, let
alone a ‘main’ one across the Island in the terms of Article III of the
Anglo-German Agreement of 1890”.

37. The Court is of the opinion that the determination of the main
channel must be made according to the low water baseline and not the
floodline (see in this regard the practice referred to in paragraph 33
above). The evidence shows that when the river is in flood, the Island is
submerged by flood water and the entire region takes on the appearance
of an enormous lake. Since the two channels are then no longer distin-
guishable, it is not possible to determine the main channel in relation to
the other channel. As for the channel described by Namibia as the main
channel, the Court finds that the largest part of its bed remains dry for
the greater part of the year. High sand bars which are among the highest
points of the Island (927 metres above sea-level) are found there, but it
must also be noted that it was in this bed that cultivation took place,
according to the evidence of a 1943 aerial photograph submitted by both
Parties. It is difficult to accept that this bed, generally dry, and which
would occupy the south-western part of the Island, can be the bed of the
main channel. The Court therefore is not persuaded by Namibia’s argu-
ment concerning the existence of this major “main” channel whose visible
southern channel would merely constitute the thalweg.

38. Namibia emphasizes the importance of the Chobe Ridge in the
area in question as a “stable and clearly visible escarpment some
50 metres high”; it uses this as an argument for determining the main
channel, by maintaining that the right bank of the southern channel,
which follows the Chobe Ridge, has certain characteristics (“a steep,
well-defined bank with a strip of riverine vegetation along it”) that make
it readily identifiable. The Court would observe that, even if one part of
the right bank of this channel is easily identifiable from a distance, other
parts of this bank are not, and neither is the left bank. The Court is there-
fore unable to conclude that, in terms of visibility — or of general physi-
cal appearance — the southern channel is to be preferred to the northern
channel.

39. The Court turns now to the criteria put forward by Botswana con-
cerning “bed profile configuration”. The Court finds that the northern
channel of the Chobe, around Kasikili/Sedudu Island, does not contain
any of the meanders that are so typical of the secondary branches of
watercourses. The southern channel, however, does show such meanders.
Namibia indeed acknowledges the curved nature of the southern channel
but, in light of the sediment deposition, draws contrary conclusions with
regard to the importance of this channel. Having examined the argu-
ments, maps and photographs put forward by the Parties, the Court is
unable to conclude that, from its bed configuration, the southern channel
constitutes the principal and natural prolongation of the course of the
Chobe before the bifurcation.

29
1071 KASIKILI/SEDUDU ISLAND (JUDGMENT)

40. The navigability of a watercourse is the combined result of its
depth, its width and the volume of water it carries, taking account of
natural obstacles such as waterfalls, rapids, shallow points, etc., along its
course. The Parties to the dispute do not accord equal importance to
navigability in the determination of the main channel of the Chobe. Bot-
swana maintains that “in the period at which the [1890] Treaty was con-
cluded . . . navigability and access to navigable waters were primary
considerations in the minds of the negotiators”. In Namibia’s view, on
the other hand, “it would be anomalous to apply a criterion of naviga-
bility to a river boundary that is non-navigable for most of its length”;
Namibia attaches no less importance to the actual use of the southern
channel of the Chobe around Kasikili/Sedudu Island for the purpose of
navigation by tourist vessels.

The Court notes that the navigability of watercourses varies greatly,
depending on prevailing natural conditions. Those conditions can pre-
vent the use of the watercourse in question by large vessels carrying sub-
stantial cargoes, but permit light flat-bottomed vessels to navigate. In the
present case, the data furnished by the Parties tend to prove that the
navigability of the two channels around Kasikili/Sedudu Island is limited
by their shallowness. This situation inclines the Court to the view that, in
this respect, the “main channel” in this part of the Chobe is that of the
two which offers more favourable conditions for navigation. In the
Court’s view, it is the northern channel which meets this criterion.

In 1947, Mr. W. Ker, the proprietor of the Zambezi Transport & Trad-
ing Company, sought permission to transport timber by barge via the
northern channel of the Chobe from Serondella (upstream) to Katam-
bora (downstream), the southern channel being unusable for that pur-
pose (see paragraph 56 below). The Court has no information regarding
the volume of timber carried, the duration of this undertaking or its suc-
cess; nor has it been informed of other attempts which may have been
made to utilize the Chobe for navigational purposes. This absence of
data enables the Court to conclude that the economic importance of
navigation, even in the northern channel, has remained slight. However,
it follows from the Trollope-Redman correspondence of 1948 — which
correspondence the Court will consider later (see paragraph 58 below) —
that the northern channel of the Chobe was regarded as a “stretch of
water... navigable and giv[ing] access to the higher reaches of the Chobe
— [unlike] the southern channel”. This correspondence also indicates
that “the Southern Channel [was] not navigable by [timber] barges when
the river [was] not in flood”.

Moreover, the use of the southern channel by flat-bottomed tourist
boats does not in itself prove that the latter offers more favourable con-
ditions for navigation than the northern channel. In the view of the
Court, the presence of these tourist boats in the southern channel is
attributable to the spectacle of large wild animals and the wealth of fauna

30
1072 KASIKILI/SEDUDU ISLAND (JUDGMENT)

on the banks of the southern channel. The economic importance of tour-
ism in the southern channel does not alter its conditions of navigability.
The Court cannot therefore regard the amount of tourist craft in the
southern channel as a reason for modifying the conclusion that it has
reached above.

4t. For the foregoing reasons, the Court concludes that, in accordance
with the ordinary meaning of the terms that appear in the pertinent pro-
vision of the 1890 Treaty, the northern channel of the River Chobe
around Kasikili/Sedudu Island must be regarded as its main channel.

42. This conclusion is supported by the results of various on-site inves-
tigations, as recorded in the reports drawn up on those occasions. The
Court will revert in greater detail to these reports when it considers their
legal significance in the course of its examination of the conduct of the
Parties subsequent to the 1890 Treaty (see paragraphs 52-70 below). At
this stage it would nonetheless note the following points:

(1) in 1912, Captain H. E. Eason, of the Bechuanaland Police, travelled
through the area in question and concluded as follows in his recon-
naissance report:

“Here [i.e., around Kissikiri (Kasikili) Island], 1 consider that un-
doubtedly the north should be claimed as the main channel. At
the western end of the island the north channel at this period of the
year is over one hundred feet wide and 8 feet deep, the south channel
about forty feet wide and four feet deep. The south channel is merely
a back water, what current there is goes round the North”

(2) a joint report drawn up on 19 January 1948 by Messrs. L. F. W.
Trollope and N. V. Redman, respectively Magistrate of the Eastern
Caprivi Strip and District Commissioner at Kasane (Bechuanaland),
contains the following conclusions on this point:

“We express the opinion that the ‘main Channel’ lies in the water-
way which would include the island in question in the Bechuanaland
Protectorate” ;

(3) the joint report drawn up on 15 July 1985 by a joint team of experts
from South Africa and Botswana resulted in the following conclu-
sion: “The main channel of the Chobe River now passes Sidudu/
Kasikili Island to the west and to the north of it.”

Thus, the three on-site surveys carried out at different times concluded
that the main channel of the River Chobe was the northern channel.

*

43. The Court will now consider how and to what extent the object
and purpose of the treaty can clarify the meaning to be given to its terms.

31
1073 KASIKILI/SEDUDU ISLAND (JUDGMENT)

While the treaty in question is not a boundary treaty proper but a treaty
delimiting spheres of influence, the Parties nonetheless accept it as the
treaty determining the boundary between their territories. The major
concern of each contracting party was to protect its sphere of influence
against any intervention by the other party and to obviate any risk of
future disputes. Article VII of the 1890 Treaty is worded as follows:

“The two Powers engage that neither will interfere with any
sphere of influence assigned to the other by Articles I to IV. One
Power will not in the sphere of the other make acquisitions, conclude
Treaties, accept sovereign rights or Protectorates, nor hinder the
extension of influence of the other.

It is understood that no Companies nor individuals subject to one
Power can exercise sovereign rights in a sphere assigned to the other,
except with the assent of the latter.”

The contracting powers, by opting for the words “centre of the main
channel”, intended to establish a boundary separating their spheres of
influence even in the case of a river having more than one channel. They
possessed only rudimentary information about the Chobe’s channels. If
they knew that such channels existed, their number, features, naviga-
bility, etc., and their relative importance remained unknown to them.
This situation explains the method adopted to define the southern bound-
ary of the Caprivi Strip.

The Court stated in the Temple of Preah Vihear ( Merits) case:

“There are boundary treaties which do no more than refer to a
watershed line, or to a crest line, and which make no provision for
any delimitation in addition.” (.C. J. Reports 1962, p. 34.)

In that Judgment the Court added that this was “an obvious and con-
venient way of describing a frontier line objectively, though in general
terms” (ibid, p. 35). In the present case, the contracting parties employed
a similar approach.

44. The Court notes that navigation appears to have been a factor in
the choice of the contracting powers in delimiting their spheres of influ-
ence. The great rivers of Africa traditionally offered the colonial powers
a highway penetrating deep into the African continent. It was to gain
access to the Zambezi that Germany sought “a strip of territory which
shall at no point be less than 20 English miles in width” — terms which
were eventually included in the provisions of Article III, paragraph 2, of
the Treaty. Admittedly, this strip of territory did provide access to the
Zambezi, but its southern boundary was formed by the Chobe River,
which was apparently assumed to be navigable, as suggested by the use of

32
1074 KASIKILI/SEDUDU ISLAND (JUDGMENT)

the word “thalweg” in the text of the German version of the Treaty. The
difficulties of the land route owing to regular flooding, and the obstacles
to navigation on the Chobe, were, in all probability, little known at the
time.

45. The fact that the words “centre of the main channel” were included
in the draft Treaty on the initiative of the British Government suggests
that Great Britain no less than Germany sought to have access to the
Zambezi. In order to mark the separation of their spheres of influence,
the contracting parties chose “the centre of the main channel” of the
Chobe, thus ensuring that there was a well-defined, recognizable bound-
ary, in a watercourse that was assumed to be navigable. There are
grounds for thinking that one of the reasons underlying their decision
was navigation, but the Court does not consider that navigation was the
sole objective of the provisions of Article III, paragraph 2, of the Treaty.
In referring to the main channel of the Chobe, the parties sought both to
secure for themselves freedom of navigation on the river and to delimit as
precisely as possible their respective spheres of influence,

*  *

46. The travaux préparatoires of the Treaty concerning south-west
Africa and the Caprivi Strip in particular support this reasoning.

Initial attempts to record the parties’ agreement described the bound-
ary simply as following the course of the Chobe, without reference to any
channel. Article II of the provisional agreement initialled by Lord Salis-
bury and Count Hatzfeldt on 17 June 1890 stipulated:

“The frontier between the German territory and the English ter-
ritory in the south-west of Africa shall follow, from the point which
has been agreed upon in previous arrangements, the 22nd degree of
south latitude (leaving Lake Ngami to England), to the east up to
the 21st degree of longitude; from thence to the north to where that
degree touches the 18th degree of south latitude. Thence, the line of
demarcation shall be carried to the east along the centre of the River
Tschobi, up to the point where it flows into the Zambesi.”

The text subsequently prepared by the British and German negotia-
tors, and transmitted to the British Foreign Office on 21 June 1890, as
“a draft of the Articles of Agreement” was worded:

“(The boundary] runs eastward along that parallel till it reaches
the River Chobe, and descends the centre of that river to its junction
with the Zambesi, where it terminates. It is understood that, under
this arrangement, Germany shall have free access from her Protec-
torate to the Zambesi by the Chobe.”

On 25 June 1890, the British side proposed the following wording: “In
33
1075 KASIKILI/SEDUDU ISLAND (JUDGMENT)

paragraph 2 of Article III, after the words ‘the River Chobe, and descends
the centre of, the words ‘the main channel of should be inserted.”

The proposal was accepted by the German side and translated as “in
der Thal-Linie des Hauptlaufes dieses Flusses”. In the end the word Thal-
Linie was replaced by the word Thalweg. The German text is therefore a
word-for-word translation of the British proposal and follows the Eng-
lish text. Therefore, it may reasonably be supposed that these terms are
synonymous and that the English text, like the German text, correctly
and accurately expresses the will of the contracting parties.

* o*

47. In the course of the proceedings, Botswana and Namibia made
abundant reference to the subsequent practice of the parties to the 1890
Treaty — and of their successors — as an element in the interpretation of
that Treaty.

48. Article 31, paragraph 3, of the 1969 Vienna Convention on the
Law of Treaties, which, as stated earlier, reflects customary law (see para-
graph 18 above), provides as follows:

“Article 31
General Rule of Interpretation
3. There shall be taken into account, together with the context:
(a) any subsequent agreement between the parties regarding the
interpretation of the treaty or the application of its provisions;
(b) any subsequent practice in the application of the treaty which
establishes the agreement of the parties regarding its interpreta-
tion;

LE)

49. In relation to “subsequent agreement” as referred to in subpara-
graph (a) of this provision, the International Law Commission, in its
commentary on what was then Article 27 of the draft Convention, stated
the following:

“an agreement as to the interpretation of a provision reached after
the conclusion of the treaty represents an authentic interpretation by
the parties which must be read into the treaty for purposes of its
interpretation” (Yearbook of the International Law Commission,
1966, Vol. II, p. 221, para. 14).

As regards the “subsequent practice” referred to in subparagraph (2) of
the above provision, the Commission, in that same commentary, indi-
cated its particular importance in the following terms:

“The importance of such subsequent practice in the application of
the treaty, as an element of interpretation, is obvious; for it consti-
tutes objective evidence of the understanding of the parties as to the

34
1076 KASIKILI/SEDUDU ISLAND (JUDGMENT)

meaning of the treaty. Recourse to it as a means of interpretation is
well-established in the jurisprudence of international tribunals.” (Op.
cit., p. 241, para. 15.)

50. Indeed in the past, when called upon to interpret the provisions of
a treaty, the Court has itself frequently examined the subsequent practice
of the parties in the application of that treaty (see, for example, Corfu
Channel, Merits, Judgement, I.C.J. Reports 1949, p. 25; Arbitral Award
Made by the King of Spain on 23 December 1906, Judgment, I.CJ.
Reports 1960, pp. 206-207; Temple of Preah Vihear, Merits, Judgment,
LC.J. Reports 1962, pp. 33-35; Certain Expenses of the United Nations
(Article 17, Paragraph 2, of the Charter), Advisory Opinion, LC J.
Reports 1962, pp. 157, 160-161 and 172-175; Military and Paramilitary
Activities in and against Nicaragua (Nicaragua v. United States of
America), Jurisdiction and Admissibility, Judgment, I C.J. Reports 1984,
pp. 408-413, paras. 36-47; Territorial Dispute (Libyan Arab Jamahiriyal
Chad), Judgment, I. C.J. Reports 1994, pp. 34-37, paras. 66-71; Legality
of the Use by a State of Nuclear Weapons in Armed Conflict, Advisory
Opinion, LC.J. Reports 1996 (I), p. 75, para. 19).

51. While the Parties to the present proceedings both accept that inter-
pretative agreements and subsequent practice do constitute elements of
treaty interpretation under international law, they disagree on the conse-
quences to be drawn from the facts in this case for purposes of the inter-
pretation of the 1890 Treaty.

%

52. In support of its interpretation of Article Ill, paragraph 2, of the
1890 Treaty, Botswana relies principally on three sets of documents: a
report on a reconnaissance of the Chobe produced in August 1912 by an
officer of the Bechuanaland Protectorate Police, Captain Eason; an
arrangement arrived at in August 1951 between Major Trollope, Magis-
trate for the Eastern Caprivi, and Mr. Dickinson, a District Commis-
sioner in the Bechuanaland Protectorate, together with the correspon-
dence that preceded and followed that arrangement; and an agreement
concluded in December 1984 between the authorities of Botswana and
South Africa for the conduct of a Joint Survey of the Chobe, together
with the resultant Survey Report.

The Court will examine each of these three sets of documents in turn,
in order to determine what conclusions may be drawn from them in the
light of the rules set out in Article 31, paragraph 3, of the Vienna Con-
vention.

53. About the year 1910, negotiations took place between Germany
and Great Britain concerning the boundary between their respective pos-
sessions in the area of the Caprivi Strip west of the intersection of the
18th parallel with the River Chobe, and arbitration of the matter was
considered.

35
1077 KASIKILI/SEDUDU ISLAND (JUDGMENT)

Anticipating a possible extension of the discussions to include the
boundary east of that point, the British Secretary of State for the Colo-
nies, in a letter dated 14 July 1911 to the High Commissioner responsible
for Bechuanaland, expressed himself in the following terms:

“I take this opportunity of observing that in the second clause of
Article III of the Anglo-German Agreement of 1890 it is stated that
the boundary ‘descends the centre of the main channel of that river
(ie., the River Chobe) to its junction with the Zambesi’. As, in this
section of its course, the River Chobe divides into more than one
channel which afterwards reunite, the question as to which is the
main channel will require consideration. I have to request . . . that
I may receive all available information from local sources in support
of the view that the north channel is the main channel. Such infor-
mation should be accompanied by a map and, if possible, by meas-
urements of the streams, and should be in a form which can, if
necessary, be laid before the arbitrator as part of the case of His
Majesty’s Government.”

This was the context in which Captain Eason was instructed to prepare
a “Report on the main channel of the Linyanti (or Chobe) river”. That
Report, which bears the date 5 August 1912, contains, inter alia, the fol-
lowing passage:

“Two miles above the rapids lies Kissikiri Island. [H]ere I consider
that undoubtedly the North should be claimed as the main channel.
At the Western end of the island the North channel at this period of
the year is over one hundred feet wide and eight feet deep, the South
channel about forty feet wide and four feet deep. The South channel
is merely a back water, what current there is goes round the North.
The natives living at Kasika in German territory are at present
growing crops on it.”

It is not disputed that Kissikiri Island is the island later known as
Kasikili/Sedudu.

54. In its Memorial, Botswana claimed that the Eason Report repre-
sented practice in the application of the 1890 Treaty. Namibia disputed
this, pointing out inter alia that Great Britain had not made any claim on
this basis, even though its exchanges with Germany concerning the rest
of the southern boundary continued until the outbreak of the First
World War. However, in the final version of its argument, Botswana,
while continuing to rely on the Eason Report for other purposes, accepted
that it could not be regarded as evidence of subsequent practice relating
to the application of the 1890 Treaty.

55. The Court shares the view that the Eason Report and its surround-

36
1078 KASIKILI/SEDUDU ISLAND (JUDGMENT)

ing circumstances cannot be regarded as representing “subsequent prac-
tice in the application of the treaty” of 1890, within the meaning of
Article 31, paragraph 3 (b), of the Vienna Convention. It notes that the
Report appears never to have been made known to Germany and to have
remained at all times an internal document. The Court observes, more-
over, that the British Government itself never took the Report any
further, whether immediately afterwards (the anticipated arbitration not
having taken place) or later on (for example when the Caprivi Strip was
occupied by British troops during the First World War, or when it was
administered by the British authorities on behalf of South Africa between
1921 and 1929).

56. In 1947, Mr. Ker, who was operating a transport business in
Bechuanaland, planned to bring timber down the Chobe using the north-
ern channel. He obtained the necessary permission from the competent
official in the Caprivi Strip, Major Trollope, but also raised the matter
with the Bechuanaland authorities. Correspondence then ensued between
Major Trollope and the Assistant District Commissioner at Maun
(Bechuanaland), Mr. Redman. In a letter dated 18 December 1947,
Mr. Redman wrote to Major Trollope as follows:

“1. F have the honour to inform you that I have received a letter
from the Zambesi Transport & Trading Company stating that they
wish to recommence the transport of timber by river from Seron-
della but they have been informed by you that the channel between
Kasane and Serondella which they intend to use, is in the Caprivi
Strip.

2. At low water I understand that this channel is the only water
connection between Kasane and Serondella and I suggest that if this
channel does happen to run into the Caprivi Strip from the Chobe
river along which our boundary runs it will be in both our interests
and a matter of convenience if we can come to an arbitrary agree-
ment that half this channel is included in this Territory for the pur-
pose of the transport of the timber by the Zambesi Transport &
Trading Company.

3. If however the channel referred to is part of the Chobe river
and not a branch off from it then it seems probable that the actual
boundary is formed by the deep water channel in the river, which
would mean that they would not be entering your Territory.

4. 1 would be glad to have your views on this matter.”

In his reply of 3 January 1948 Major Trollope informed Mr. Redman
that he was prepared to renew indefinitely the permission originally given
to Mr. Ker for a period of six months; and he added:

“4. In regard to the larger question raised by you (i.e. as to
whether the stretch of water in question is actually within the East-

37
1079

57

KASIKILI/SEDUDU ISLAND (JUDGMENT)

ern Caprivi Zipfel, — or whether it in fact forms the boundary),
I freely admit that the matter is not without difficulty. I further agree
that it is a matter affecting our two administrations and is not
merely a matter between this office and Mr. Ker.

5. I suggest, in this connection, that I and your Assistant at
Kasane, should hold a joint informal investigation thereafter sub-
mitting reports (joint if we are able to reach unanimity) to our
respective administrations in order to resolve the matter finally
and officially.”

. On 19 January 1948, Major Trollope and Mr. Redman (at the time

District Commissioner at Kasane, Bechuanaland) produced a Joint
Report entitled “Boundary between the Bechuanaland Protectorate and
the Eastern Caprivi Zipfel: Kasikili Island”, in which, after citing the
provisions of Article III, paragraph 2, of the 1890 Treaty, they stated the

follo

38

wing:

“3. We find after separate examination of the terrain and the
examination of an aerial photograph that the ‘main Channel’ does
not follow the waterway which is usually shown on maps as the
boundary between the two Territories.

4. We express the opinion that the ‘main Channel’ lies in the
waterway which would include the island in question in the Bech-
uanaland Protectorate.

5. On the other hand we are satisfied, after enquiry that since at
least 1907, use has been made of the Island by Eastern Caprivi Zipfel
tribesmen and that that position still continues.

6. We know of no evidence of the Island having been made use
of, or claimed, by Bechuanaland Tribesmen or Authorities or of any
objection to the use thereof by Caprivi Tribesmen being made.

7. We record, however, the fact that the country on the Bech-
uanaland side of the boundary is for all practical purposes not
tribally occupied by Africans.

8. We record the foregoing as facts particularly recording that we
have neither arrived at, nor expressed any joint opinion on the effect
of these facts on the ownership of the Island.”

. Major Trollope sent a copy of the Report to the Secretary of

Native Affairs at Pretoria under cover of a letter of 21 January 1948, in

whic

38

h he stated inter alia the following:

“(T]he terms of the Treaty are very definitive and, as I have
already pointed out, favour the Bechuanaland contention. It is not
without point, however, that we are — by occupation — in the posi-
tion of the possessor and the onus would appear to lie on the Pro-
tectorate to prove their case in order to disturb our possession.”
1080 KASIKILI/SEDUDU ISLAND (JUDGMENT)

He proposed various solutions, after first pointing out that “[t]he Bech-
uanaland authorities are anxious to have the northern channel recognised
as the boundary because that stretch of water is navigable and gives
access to the higher reaches of the Chobe — which is not the case in
respect of the southern channel”.

For his part, Mr. Redman forwarded a copy of the Joint Report to the
Government Secretary at Mafeking, under cover of a letter of 26 January
1948, in which he stated inter alia that: “the Southern Channel [was] not
navigable by [Mr. Ker’s] Barges when the river [was] not in flood” and
that it was “even difficult for small craft to navigate it”; that “the map,
which show[ed] the boundary to follow the Southern Channel, [was] . . .
inaccurate and [had] probably [been] drawn by some-one who had not
examined the river to determine the main Channel”; that according to
“further information from an inhabitant of the Island... in 1924 a
Caprivi Chief... [had] applied to . . . the Resident Magistrate at Kasane,
for permission for his people to plough on the Island”; and that “surren-
der of this Island would prevent this Territory from having free use of the
Chobe River, which [might] one day become an extremely important
waterway’.

59. After Major Trollope and Mr. Redman forwarded the Joint Report
of 19 January 1948 to their respective authorities, there ensued an
extended correspondence between those authorities.

On 14 October 1948 the Secretary to the South African Prime Minister
with responsibility for External Affairs wrote to the Administrative Sec-
retary to the High Commissioner for Bechuanaland in Pretoria, stating
that, while he noted the findings of the Trollope-Redman Report with
regard to the identification of the “main channel” around Kasikili Island,
he wished to propose an arrangement in the following terms:

“The Union Government is anxious to preserve the rights of the
Caprivi Zipfel tribesmen on the Island and it is understood that the
Bechuanaland authorities desire the use of the Northern channel for
navigation purposes. As there would appear to be no conflict of
interests it should be possible to come to an arrangement which is
mutually satisfactory. Your views in the matter would be appre-
ciated.”

The Administrative Secretary replied on 4 November 1948 that

“the Resident Commissioner of the Bechuanaland Protectorate has
directed the Assistant District Commissioner, Kasane, that tribes-
men of the Caprivi Zipfel should be allowed to cultivate land on
Kasikili Island, if they wish to do so, under an annual renewable
permit”.

This reply did not appear to satisfy the Secretary for External Affairs of
South Africa, who wrote back to the Administrative Secretary on 14 Feb-
ruary 1949 in the following terms:

“While noting that your Administration is prepared to authorise

39
1081 KASIKILI/SEDUDU ISLAND (JUDGMENT)

Caprivi Zipfel tribesmen to cultivate land on Kasikile Island on an
annual renewable permit, I am to state that this is not what the
Union Government had in mind.

From the available information it is clear that Caprivi Tribesmen
have made use of the Island for a considerable number of years and
that their right to do so has at no time been disputed either by
Bechuanaland Tribesmen or the Bechuanaland authorities.

It was further understood that the interests of the Bechuanaland
authorities centred in the use of the Northern Channel of the Chobe
for navigation purposes.

My object in writing to you was therefore to ascertain whether
agreement could not be reached on the basis of your Administration
recognising the Union’s claim to Kasikile Island subject to it issuing
a general permit for the use of the Northern waterway for navigation
purposes.”

On 6 June 1949 the High Commissioner for Bechuanaland wrote to the
Secretary of State for Commonwealth Relations in London informing
him of the South African proposal. In his letter the High Commissioner
stated that the Union Government had “proposed a slight adjustment of
the northern boundary of the Bechuanaland Protectorate”; he explained
that Kasikili Island had “hitherto been regarded as part of the Caprivi
Zipfel, since maps show{ed] that the main channel pass[ed] to the south of
the island”; with reference to the Joint Report of 19 January 1948, which
he enclosed with his letter, he stated that

“[t]he question of the correct boundary was raised by a firm which
intends to transport timber down the river, and the Union Govern-
ment, having examined the question, find that the main channel is to
the north of the island, and that there has been no change in the
course of the channel within living memory”;

and he concluded:

“4. The Resident Commissioner of the Bechuanaland Protectorate
considers that the Union proposal to set the boundary in the south-
ern channel need not be resisted, if the use of the northern channel
for navigation is guaranteed for the inhabitants and Government of
the Bechuanaland Protectorate. This guarantee the Union Govern-
ment are prepared to give.

5. I consider in the circumstances that the proposal of the Union
Government is acceptable, and would be glad to have your approval
of it.”

Ultimately, following consultations with the Commonwealth Relations
Office, Bechuanaland declined to accept the South African proposal. This
reaction appears to have been motivated, in particular, by difficulties in

40
1082 KASIKILI/SEDUDU ISLAND (JUDGMENT)

connection with the Mandate over South West Africa. Thus, in a letter
dated 24 August 1949, the Chief Secretary to the High Commissioner for
Bechuanaland explained to the Secretary to the South African Prime
Minister, that “while the slight alteration proposed [by the South African
Government] seem[ed] of little intrinsic importance, an examination of
the legal and political aspects ha[d] revealed that certain difficulties
[might] ensue both from the standpoint of international law and as
regards possible uncertainty of jurisdiction”. These points were explained
as follows in a long letter dated 20 October 1949 from the Common-
wealth Relations Office in London to the High Commissioner for
Bechuanaland:

“we agree that this very slight alteration is of no intrinsic importance
in itself and seems in substance unobjectionable. There are, however,
certain legal and political complications which it seems necessary to
bring to your notice . . . First, there is the international aspect .. .
Under Article 7 of the Mandate no modification could be made
without the consent of the Council of the League of Nations. In so
far as the mandate is still operative, this might be interpreted as
referring to some organ of the United Nations or as making any
adjustment impossible. No doubt it is unlikely that anyone would
raise any objection in the United Nations, especially as the proposal
is to add to the territory and not in any way to reduce its area, but
the possibility cannot be entirely ignored. Secondly, it is necessary to
consider the effect of the adjustment from the point of view of
Municipal Law. This is more difficult. The island is apparently
inhabited and no doubt offences are sometimes committed and civil
disputes might occur... . The matter being thus dependent on an
agreement between the United Kingdom and Germany, at first sight
there is no reason why an adjustment, fully effective for the purposes
of Municipal Law, should not be made by a further agreement
between the United Kingdom and the Union of South Africa. Unfor-
tunately, however, the International Law on the subject affects the
Municipal Law, for the mandate creates a technical difficulty . . .
The issue of an Order in Council involving a cession of territory,
however small or nominal, to South West Africa is open to some
objection since the publicity involved might arouse curiosity and
subsequent criticism on the part of those who dislike the Union
Government’s refusal to place South West Africa under trusteeship.”

On 10 May 1951 the High Commissioner wrote in similar terms to the
Secretary to the South African Prime Minister, stating that:

41
1083 KASIKILI/SEDUDU ISLAND (JUDGMENT)

“The possibility of making a declaration on behalf of the Govern-
ment of the Bechuanaland Protectorate to the effect that the Island
is not claimed as lying within the boundaries of the Protectorate has
been examined by the Legal Advisers to the Secretary of State for
Commonwealth Relations. I am afraid that they have found this
proposal to be beset by legal complications of an international
nature, the solution of which would entail difficulties disproportion-
ate to the importance of the matter at issue”:

and adding:

“The Bechuanaland Protectorate Government might possibly wish
to arrange for some land on the Island at some time to be cultivated
by the few African public servants at Kasane. Apart from this minor
matter, I venture to suggest that it is unlikely that any development
in the foreseeable future will damage the interests of the Caprivi
tribesmen who have in the past used the Island. It should, I think, be
possible to adjust by administrative action any difficulty arising in
connection with the Island and the adjacent waterway without an
alteration of the existing legal position . . . and it is assumed that the
free use of the main channel of the Chobe, to the north of the Island,
would continue to be assured under the international rules govern-
ing waterways that form the common boundary of two states.”

60. It was in very similar terms that Mr. Dickinson, who had in the
meantime succeeded Mr. Redman as District Commissioner at Kasane
(Bechuanaland) wrote on 5 July 1951 to Major Trollope “in regard to
Kasikili Island”. After explaining that “the legal complications which are
of an international nature, and beset the question of excorporating
Kasikili Island from the Bechuanaland Protectorate, will involve difficul-
ties disproportionate to the matter at issue”, he concluded as follows:

“Might I therefore say that the position as at the moment, allow-
ing the full use of the Island to your tribesmen, for grazing and cul-
tivation and our undisputed use of the Northern Waterway, under
the international laws, governing the Waterways forming the com-
mon boundaries of two states, would appear entirely satisfactory, to
the B.P. Government, and I trust also to yours.”

In his reply of 4 August 1951 Major Trollope agreed that “the ‘stink’
[was] quite disproportionate to the importance of the matter at issue”,
adding that they should “let the whole matter lapse into the decent
obscurity from which it should never have been allowed to emerge”.
However, he disagreed with certain of the language used in Mr. Dickin-
son’s letter, observing:

42
1084 KASIKIL/SEDUDU ISLAND (JUDGMENT)

“I find it, however, somewhat embarrassing to agree formally that
we should be ‘allowed’ the use of the Island and should recognise the
‘undisputed use of the Northern Waterway under the international
laws governing the waterways forming the common boundary of
two states’. Such an agreement might quite possibly be arguably
used in support of a submission that we occupy by licence and per-
mission — which we do not, of course, admit.”

Major Trollope accordingly proposed the following “gentlemen’s agree-
ment”:

“(a) That we agree to differ on the legal aspect regarding Kasikili
Island, and the concomitant question of the Northern Water-
way;

(6) That the administrative arrangements which we hereafter make
are entirely without prejudice to the rights of the Protectorate
and the Strip to pursue the legal question mentioned in (a)
should it at any time seem desirable to do so and will not be
used as an argument that either territory has made any admis-
sions or abandoned any claims; and

(c) That, having regard to the foregoing, the position revert to
what it was de facto before the whole question was made an
issue in 1947 — i.e. that Kasikili Island continue to be used by
Caprivi tribesmen and that the Northern Waterway continue
to be used as a ‘free for all’ thoroughfare.”

Major Trollope made it clear that:

“this ‘gentlemen’s agreement’ could only purport to affect arrange-
ments as between our two Administrations. I have my gravest doubts
as to the wisdom of making the ambit larger for that would bring in
all sorts of extraneous questions of international law and such like
imponderables which | think we might usefully leave for considera-
tion when we come to that bridge.”

In a letter of 11 August 1951 Mr. Dickinson stated that the three-point
agreement proposed by Major Trollope seemed to him “the most reason-
able solution” and that he “agree[d] entirely with fit]. He suggested,
however, that a paragraph (d) be added, stating “that nothing in the pre-
vious three sections should be read as preventing the [Bechuanaland Pro-
tectorate] Tribesmen using the Island for ploughing purposes”.

On 23 August 1951 Major Trollope replied as follows:

“1. Pm afraid that the point you raise rather throws a spanner in
the works.
2. ] appreciated the position as that we both wished to restore the

43
1085 KASIKILI/SEDUDU ISLAND (JUDGMENT)

factual position to what it was before Ker raised the hornet’s nest,
and to leave the /ega/ position ‘in the air’ to be freely raised in the
future by either side should that become necessary or desirable.

3. Whatever the /ega/ position (i.e. whether your tribesmen have
any rights) is, the factual position is that not in all the years past —
not in German times, nor when the Strip was administered by the
B.P., nor in the S.W. African days nor during my administration
(Union) — have B.P. tribesmen ever cultivated the Island or asserted
a right to do so; while Caprivi tribesmen have always done so (see
paras. five and six of the Joint Report of 19/1/1948 by Redman and
myself). For me to agree therefore that there is nothing to prevent
B.P. tribesmen from cultivating the Island does not seem to me to
restore the Status quo...”

To this, Mr. Dickinson responded on 3 September 1951 as follows:

“I must concede your point rather than allow the ‘spanner’ to
‘bust’ the works.

Your paragraphs (a),(b), & (c) will then meet the points in ques-
tion. In other words we revert to the position as it was prior to this
disturbance.

I feel I must make one point clear to you. Although accepting the
position and being prepared to honour it, in any discussion or con-
troversy on this Island in future, our Government will be adamant in
its attitude that the Island is B.P. — and any attitude in regard to
our ‘Administrative Settlements’ will of course be based on that
fact.”

Finally, on 13 September 1951, Major Trollope wrote as follows to the

new District Commissioner at Kasane, Mr. McLaren:

44

“2, I really feel that the possibility of future ‘discussion or contro-
versy” regarding Kasikili is extremely remote. After all the present
factual position, to which happily we now return, has existed for
generations without any conflict — indeed, in my opinion, even the
recent contretemps was unnecessary.

3. However, if circumstances again make it necessary for contro-
versy to rear its head, the fact of Dickinson’s caveat is now on
record. Perhaps it would not be inappropriate were I likewise for-
mally to record that in any future controversy over this Island, the
Caprivi will be equally insistent on asserting the legality of the fac-
tual possession and use it has enjoyed for so many years.
1086 KASIKILI/SEDUDU ISLAND (JUDGMENT)

5. I propose now, if you agree, advising my Department that
there is no necessity for pursuit of the matter at high levels as a suit-
able administrative arrangement, without any prejudice whatever to
either side, has been concluded between my office and yours ...

P.S. It occurs to me that the most likely way in which, unwittingly
and not designedly, the controversy might be re-opened is by a B.P.
tribesman ‘trespassing’ (as it would be regarded by us, although not
legally by you) on Kasikili. | hereby undertake that should any such
occasion arise [ will not deal with the matter without prior reference
to your office to ascertain whether you wish the large question
raised. May I tentatively suggest that you advise your tribesmen to
avoid any such action — unless, of course, it is deliberately done as
an assertion of right to test the position.”

This resulted in the despatch of a letter dated 20 November 1951 from
the Government Secretary at Mafeking to the District Commissioner at
Kasane, which included the following passage:

“The Native Commissioner Eastern Caprivi Zipfel may therefore
be informed that his recommendation is accepted.

2. It 1s understood that the only Africans in the Protectorate
interested in the cultivation of the Island are Government employees
living at Kasane and I am to say that they should be instructed that
they will not be permitted to plough on the Island.”

61. Each of the Parties to the present proceedings relies on the Trol-
lope-Redman Joint Report and the correspondence relating thereto in
support of its position. The consequences that they draw from them,
however, differ significantly. According to Botswana, these documents
show that the boundary around Kasikili/Sedudu Island follows the north-
ern channel; Namibia disputes this, claiming that those same documents
demonstrate that the Island forms part of the Caprivi Strip.

62. From the various administrative and diplomatic documents
referred to above, the Court, for its part, observes the following: (1) prior
to 1947 no differences had arisen between Bechuanaland and the power
administering the Caprivi Strip with regard to the boundary in the area
of Kasikili/Sedudu Island; (2) it appears that, on the basis of the maps
available at the time, the boundary had until then been supposed to be
located in the southern channel of the Chobe; (3) in 1948 a local official
from the Caprivi and a local official from Bechuanaland came to the joint
conclusion, “[alfter separate examination of the terrain and the examina-
tion of an aerial photograph”, that the “main channel” around Kasikili/
Sedudu Island was the northern one (without specifying what criteria
they had employed); at the same time they noted that since at least 1907

45
1087 KASIKILI/SEDUDU ISLAND (JUDGMENT)

use had been made of the Island by Caprivi tribesmen without objection
by the Bechuanaland authorities and that that situation still continued;
and they recorded that they had “neither arrived at, nor expressed any
joint opinion on the effect of these facts on the ownership of the Island”:
(4) the higher authorities in Bechuanaland subsequently took the view
that the boundary around the Island was located in the northern channel
of the Chobe, and that South Africa’s claims to the Island itself were un-
founded under the 1890 Treaty; nevertheless, they were initially inclined
to accept those claims, on condition that they retained access to the
northern channel, but later, after consulting London, they abandoned
that idea, fearing that this would result in a modification of the boundary
that, in view of the mandate over South West Africa, would give rise to a
variety of complications; (5) the higher authorities in South Africa, while
not disputing the possibility of the “main channel” around Kasikili/
Sedudu Island being the northern one and at the same time demonstrat-
ing a flexible attitude with regard to access to that channel, clearly
asserted their claims to the Island; (6) the local officials in the Caprivi
Strip and in Bechuanaland, aware of the positions of their respective
superior authorities but keen to remain on neighbourly terms, agreed to
shelve their legal differences and to maintain, until further notice, the
status quo ante (use of Kasikili/Sedudu Island by Caprivi tribesmen and
open access to the northern channel of the Chobe); (7) the local official in
the Caprivi Strip described the question of the “Northern Waterway” as
“concomitant” with that of the “legal aspect regarding Kasikili Island”,
and his counterpart in Bechuanaland did not challenge this; (8) the issue
of access to the Island by Bechuanaland tribesmen was not pursued
further.

63. From all of the foregoing, the Court concludes that the above-
mentioned events, which occurred between 1947 and 1951, demonstrate
the absence of agreement between South Africa and Bechuanaland with
regard to the location of the boundary around Kasikili/Sedudu Island
and the status of the Island. Those events cannot therefore constitute
“subsequent practice in the application of the treaty fof 1890} which
establishes the agreement of the parties regarding its interpretation”
(1969 Vienna Convention on the Law of Treaties, Art. 31, para. 3 (b)).
A fortiori, they cannot have given rise to an “agreement between the
parties regarding the interpretation of the treaty or the application of its
provisions” (ibid, Art. 31, para. 3 (a/).

64. In October 1984 an incident during which shots were fired took
place between members of the Botswana Defence Force and South Afri-
can soldiers who were travelling by boat in the Chobe’s southern channel.
At a meeting held in Pretoria on 19 December 1984 between representa-
tives of various South African and Botswanan ministries, it emerged that
the incident had arisen out of differences of interpretation as to the pre-
cise location of the boundary around Kasikili/Sedudu Island. At this
meeting, reference was made to the terms of the 1890 Treaty and it was

46
1088 KASIKILI/SEDUDU ISLAND (JUDGMENT)

agreed “that a joint survey should take place as a matter of urgency to
determine whether the main Channel of the Chobe River is located to the
north or the south of the Sidudu/Kasikili Island”.

The joint survey was carried out at the beginning of July 1985. The
“survey report”, drawn up on 15 July 1985, was preceded by an analysis
of the available maps stating that, while those prior to 1975 located the
boundary in the southern channel, Botswana had in 1975 published a
map which placed the boundary to the north and west of the Island: it
was concluded from this that “[t]he disparity in the depiction of the
boundary between South African maps and those of Botswana had]
probably been a contributory factor in the recent border incident near
Kasane”. Furthermore, the report was also preceded by a para-
graph entitled “Authority for Survey”, which stated:

“At an intergovernmental meeting held in Pretoria on 19 Decem-
ber 1984 it was decided that a joint survey should be undertaken to
determine whether the main channel of the Chobe River is located to
the north or the south of Sidudu/Kasikili Island.

Representatives of the two national survey organisations accom-
panied by co-workers from the Departments of Water Affairs have
now been to the area to survey the ‘Thalweg’ in the vicinity of the
island. Specific mention is made to the Thalweg in the 1890 Agree-
ment between England and Germany.”

The report itself gave details of the cross-sections and depth soundings
taken and the equipment used; it contained inter alia the following
passage:

“Livestock from Caprivi are swum across the river when grazing
on the Caprivi side is poor. The impression was gained that visits to
the Island had, in recent years, become infrequent. Benson Mafwila
[an elderly inhabitant of Kabuta village] recounted that Tax had
been paid at Kasane in the Nineteen-twenties. He was referring, no
doubt, to the period 1922-1929 when the Caprivi Strip was admin-
istered on behalf of South Africa by the Protectorate Government.
The name by which the Island is known to Caprivians is Kasikili.
This is also the Caprivian name for the arm of the river which flows
around the island to the west and north. The name Sidudu Island
is a later name coming from the Botswana side. There is a Sidudu
valley in the immediate vicinity to the south.”

The conclusions of the survey report were as follows:

“The main channel of the Chobe River now passes Sidudu/Kasikili
Island to the west and to the north of it. (See annexed Map C.)

The evidence available seems to point to the fact that this has been
the case, at least, since 1912.

47
1089 KASIKILI/SEDUDU ISLAND (JUDGMENT)

It was not possible to ascertain whether a particularly heavy flood
changed the course of the river between 1890 and 1912. Capt Eason
of the Bechuanaland Protectorate Police states, on page 4 of Part I
of the report which has been referred to earlier, that floods occurred
in 1899 and in June and July of 1909.

If the main channel of the river was ever situated to the south of
the island, it is probable that erosion in the Sidudu Valley, the loca-
tion of which can be seen in the annexed Map C, has caused the
partial silting up of the southern channel.

Air photographs showing the channels of the river in the vicinity
of the island are available in the archives of the two national survey
organisations. They were taken in 1925, 1943, 1972, 1977, 1981 and
1982. No substantial change in the position of the channels is evi-
dent from the photographs.”

65. The Department of External Affairs of Botswana officially
forwarded a copy of this joint survey to South Africa’s Department of
Foreign Affairs under cover of a Note dated 4 November 1985
which included the following passage:

“The Department of Foreign Affairs will recall that one of the
decisions taken at the meeting on 19 December was to send a joint
team of technical experts to the Chobe to determine the boundary
between Botswana and Namibia in the Sidudu/Kasikili Island area.
The Department of External Affairs is pleased to attach to this Note
copy of the report produced by the joint team of experts together
with its annexures and would be grateful to know whether or not the
South African sides wishes to have a meeting called to adopt the
report formally. Alternatively the South African side could simply
signify its acceptance of the conclusions of the report by means of a
Diplomatic Note.”

66. It would appear that South Africa never responded to this Note.
On 13 October 1986 officials of the ministries of foreign affairs of Bot-
swana and South Africa held a meeting at which the matter of Kasikili/
Sedudu Isiand was briefly discussed. According to the record of this
meeting drawn up by the Botswana side, the head of the South African
delegation “suggested the maintenance of the status quo till political cir-
cumstances could permit direct negotiations between Botswana and inde-
pendent Namibia”; the head of the Botswana delegation replied “that
there was no more room for negotiations because a joint Botswana-
South Africa team of experts had confirmed that the Island belonged to
Botswana”; and the South African representative “[dJecided to go back
to look at this question once again”.

On 22 October 1986 the Botswana authorities sent a telex to Pretoria
in which they referred to the discussions of 13 October and went on to
say:

48
1090 KASIKILI/SEDUDU ISLAND (JUDGMENT)

“It will be recalled that the Botswana side submitted that Sidudu/
Kasikili Island is part of the territory of Botswana, as confirmed by
the Botswana/South Africa Joint Team of Experts which reported to
the two Governments in July, 1985. [We] wish to inform [you] that
the Government of Botswana has since occupied Sidudu/Kasikili
Island and expects the Government of South Africa to respect the
sovereignty and territorial integrity of the Republic of Botswana in
respect of the Island.”

The South African authorities replied in the following terms:

“__ The Sidudu/Kasikili border issue addresses the international
boundary between Botswana and South West Africa/Namibia.

— According to International Law, such cases should be discussed
between the two countries concerned. It is therefore suggested
that the Cabinet of South West Africa/Namibia should be
approached by the Botswana Government for a proper resolu-
tion of the matter under consideration.

— Alternatively, the South African Government would be willing
to convene a meeting where Botswana, South West Africa/
Namibia and South Africa could all be represented and where
the relevant issue could be finalised.”

The exchange ended with a telex from the Botswana authorities dated
25 November 1986, which read as follows:

“The joint Botswana/South Africa team of experts were never
asked to demarcate an international boundary but ‘to determine
whether the main channel of the Chobe River is located to the north
or south of Sidudu Island’. The Joint Team confirmed what had
always been the fact, namely that the main channel is located to the
north of the island, and that is where the boundary is.

It is therefore clear that adequate clarification of the matter has
been made to satisfy normal requirements and no further discussion
of the matter is necessary.”

67. In these proceedings, Botswana contends that the decision taken
in December 1984 to carry out a joint survey, and all the documents
relating to that decision — including the survey of July 1985 itself — con-
stitute an “intergovernmental agreement . . . between the parties regard-
ing . .. the application” of the 1890 Treaty, which confirmed that the
boundary around Kasikili/Sedudu Island was located in the northern
channel of the Chobe. Botswana points out inter alia that “general inter-
national law dofes] not require any particular formality for the conclu-
sion of an international agreement” and that “[t}he only criterion is the
intention of the parties to conclude a binding agreement and this can be
inferred from the circumstances”.

49
1091 KASIKILI/SEDUDU ISLAND (JUDGMENT)

Namibia categorically denies that the discussions conducted between
the Botswana and South African authorities in 1984-1985 led to an agree-
ment on the boundary; it stresses in this connection that the July 1985
joint survey was not “self-executing” and was devoid of any legally bind-
ing status unless the parties concerned took the appropriate measures to
confer such status upon it. Namibia points out that, once the United
Nations General Assembly had terminated South Africa’s mandate over
South West Africa in 1966, neither South Africa nor Botswana could in
any case conclude any kind of agreement on the boundaries of this ter-
ritory.

68. Having examined the documents referred to above, the Court can-
not conclude therefrom that in 1984-1985 South Africa and Botswana
had agreed on anything more than the despatch of the joint team of
experts. In particular, the Court cannot conclude that the two States
agreed in some fashion or other to recognize themselves as legally bound
by the results of the joint survey carried out in July 1985. Neither the
record of the meeting held in Pretoria on 19 December 1984 nor the
experts’ terms of reference serve to establish that any such agreement was
reached. Moreover, the subsequent correspondence between the South
African and Botswana authorities appears to deny the existence of any
such agreement: in its Note of 4 November 1985 (see paragraph 65
above), Botswana called upon South Africa to accept the survey conclu-
sions; not only did South Africa fail to accept them but on several occa-
sions it emphasized the need for Botswana to negotiate and agree on the
question of the boundary with the relevant authorities of South West
Africa/Namibia, or indeed of the future independent Namibia.

69. The Court has reached the conclusion that there was no agreement
between South Africa and Botswana “regarding the . . . application of
the [1890 Treaty]. This is in itself sufficient to dispose of the matter. It is
unnecessary to add that in 1984 and 1985 the two States had no compe-
tence to conclude such an agreement, since at that time the United
Nations General Assembly had already terminated South Africa’s Man-
date over South West Africa by resolution 2145 (XXI) of 27 October
1966, and the Security Council had approved that measure by resolution
276 (1970) of 30 January 1970. The Court itself, in its Advisory Opinion
of 21 June 1971 on the Legal Consequences for States of the Continued
Presence of South Africa in Namibia (South West Africa) notwithstana-
ing Security Council Resolution 276 (1970), stated the following in this
regard:

“(1) ... the continued presence of South Africa in Namibia being
illegal, South Africa is under obligation to withdraw its admin-
istration from Namibia immediately and thus put an end to its
occupation of the Territory;

(2) ... States Members of the United Nations are under obligation

50
1092 KASIKILI/SEDUDU ISLAND (JUDGMENT)

to recognize the illegality of South Africa’s presence in Namibia
and the invalidity of its acts on behalf of or concerning Namibia,
and to refrain from any acts and in particular any dealings with
the Government of South Africa implying recognition of the
legality of... such presence and administration” (1. C.J. Reports
1971, p. 58, para. 133).

Furthermore, the evidence indicates that the Botswana Government’s
preliminary contacts with the President of the United Nations Council
for Namibia and the United Nations Commissioner for Namibia with a
view to obtaining their approval prior to the Pretoria meeting of
19 December 1984 were not pursued further, and did not have the result
sought by Botswana.

70. Nor does the Court need to examine any further Botswana’s alter-
native argument that, even if the 1984-1985 “agreement” was invalid, it
had been “adopted” by Namibia, first before the Joint Team of Technical
Experts in 1994, then before the Court itself. The Court need only
observe that no such “adoption” by Namibia has been established.

*

71. In the proceedings Namibia, too, invoked in support of its argu-
ments the subsequent practice of the parties to the 1890 Treaty. In its
Memorial it contended that this conduct

“is relevant to the present controversy in three distinct ways. In
the first place, it corroborates the interpretation of the Treaty . ..
Second, it gives rise to a second and entirely independent basis
for Namibia’s claim under the doctrines concerning acquisition of
territory by prescription, acquiescence and recognition. Finally, the
conduct of the parties shows that Namibia was in possession
of the Island at the time of termination of colonial rule, a fact that
is pertinent to the application of the principle of uti possidetis.”

At the hearings Namibia stressed that “its primary claim is that its title is
treaty-based”, the claim “of prescription [being] asserted in the alterna-
tive”; and it argued in this regard that

“the very meaning of the ability to plead in the alternative is that
each claim is to be considered in its own right, and no inference is to
be taken against one claim because an inconsistent claim has been
pleaded”.

The subsequent practice relied on by Namibia consists of

51
1093 KASIKILI/SEDUDU ISLAND (JUDGMENT)

“[tlhe control and use of Kasikili Island by the Masubia of Caprivi,
the exercise of jurisdiction over the Island by the Namibian govern-
ing authorities, and the silence by Botswana and its predecessors
persisting for almost a century with full knowledge of the facts . . .”

Namibia contends that the members of the Masubia tribe — a people
from the eastern part of the Caprivi Strip — had a “continued presence”
on the Island at least between 1890 and the late 1940s. Citing various
official documents, explorers’ accounts and testimony of witnesses, it
states that: “from the beginning of the colonial period at least, and prob-
ably a good deal further back than that, Kasikili Island was agricultural
land cultivated by the people occupying what is now the Eastern Caprivi” ;
that “[t]heir occupation was continuous, exclusive and uninterrupted, in
so far as the physical conditions of the Island allowed” ; and that “Kasikili
Island/Kasika [a Caprivi village] was a well organized village community,
with a chief and at times with a school — its centre of gravity moving
from one pole to the other in accordance with the dictates of the annual
flood”. According to Namibia, Germany from 1909, then its successors
after 1915, incorporated the local institutions of the Masubia into the
structure of colonial governance, using them as instruments for exercising
their authority. The Masubia thus constituted a key component of the
system of “indirect rule” which prevailed in the region. Namibia empha-
sizes that all these facts were known to the Bechuanaland authorities just
across the Chobe, in Kasane, and that they made no objection or protest,
at least until the late 1940s. And Namibia concludes that:

“[t]he continued control and use of Kasikili Island by the people of
the Eastern Caprivi, the exercise of jurisdiction over the Island by
the governing authorities in the Caprivi Strip, and the continued
silence of those on the other side of the Chobe . . . confirm the inter-
pretation of the Treaty . . . [whereby] Article HI. . . attributes
Kasikili Island to Namibia”.

72. Botswana, for its part, observes that

“Tt]he Namibian argument based upon subsequent conduct of the
parties rests upon extraordinarily weak foundations, both in concep-
tual and in factual terms. The conceptual foundations are weak
because in truth, the ‘subsequent conduct’ argument of Namibia is
an argument grounded in acquisitive prescription. Thus, subsequent
conduct, which relates to an existing legal instrument, is opposed to
prescription, the purpose of which is to destroy and to supplant a
pre-existing title.”

It does not dispute that people from the Caprivi at times used the Island
for agricultural purposes, but it stresses the sporadic nature of that use

52
1094 KASIKILI/SEDUDU ISLAND (JUDGMENT)

and claims that the same applied to people living on the other side of the
Chobe, in Bechuanaland. At all events, Botswana denies categorically
that there was ever a permanent settlement or a village on Kasikili/
Sedudu Island. And it concludes that the Eason Report of 1912, the dip-
lomatic transactions of 1948 to 1951, and other pieces of evidence “all...
establish conclusively that in administrative terms the Island always
formed part of Botswana and its predecessor, the Bechuanaland Protec-
torate”.

73. At this point in its Judgment, the Court will not examine Namibia’s
argument concerning prescription (see in this respect paragraphs 90-99
below). It will merely seek to ascertain whether the long-standing,
unopposed, presence of Masubia tribespeople on Kasikili/Sedudu Island
constitutes “subsequent practice in the application of the [1890] treaty
which establishes the agreement of the parties regarding its interpre-
tation” (1969 Vienna Convention on the Law of Treaties, Art. 31,
para. 3 (b)).

74. To establish such practice, at least two criteria would have to be
satisfied: first, that the occupation of the Island by the Masubia was
linked to a belief on the part of the Caprivi authorities that the boundary
laid down by the 1890 Treaty followed the southern channel of the
Chobe; and, second, that the Bechuanaland authorities were fully aware
of and accepted this as a confirmation of the Treaty boundary.

While it is true that the early maps of the region placed the boundary
around Kasikili/Sedudu Island in the southern channel of the Chobe,
none of them officially interpreted the 1890 Treaty (see paragraph 84
below), and the evidence would tend rather to suggest that the boundary
line was shown as following the southern channel as a result of the inter-
mittent presence on the Island of people from the Caprivi Strip. How-
ever, there is nothing that shows, in the opinion of the Court, that this
presence was linked to territorial claims by the Caprivi authorities. It is,
moreover, not uncommon for the inhabitants of border regions in Africa
to traverse such borders for purposes of agriculture and grazing, without
raising concern on the part of the authorities on either side of the border.

Furthermore, the Court is mindful that, already in 1912, when Great
Britain was concerned with determining the boundary of the Bechuana-
land Protectorate in the area in question, Captain Eason of the Bechua-
naland police stated that “the North should be claimed as the main chan-
nel” of the Chobe around Kasikili/Sedudu Island (which, in view of the
terms of the 1890 Treaty, placed the Island in Bechuanaland territory),
while at the same time observing — without apparently seeing this as
being in any way a problem — that “[t]he natives living at Kasika in Ger-
man territory [welre . . . growing crops on it” (see paragraph 53 above).
There were similar statements in the Trollope-Redman Report of 19 Janu-
ary 1948, in which the two officials expressed the view that “the ‘main
channel’ lies in the waterway which would include the island in question

53
1095 KASIKILI/SEDUDU ISLAND (JUDGMENT)

in the Bechuanaland Protectorate”; at the same time, they noted that
“use hafd] been made of the Island by Eastern Caprivi Zipfel tribesmen”
without objection from Bechuanaland (see paragraph 57 above). Finally,
the joint survey report on the Chobe drawn up by South African and
Botswanan experts on 15 July 1985 in the context of discussions on the
location of the boundary around Kasikili/Sedudu Island noted that “[lJive-
stock from Caprivi [we]re swum across the river when grazing on the
Caprivi side [wa]s poor”; at the same time it suggested that “visits to the
Island had, in recent years, become infrequent” (see paragraph 64 above).
It would therefore seem that, as far as Bechuanaland, and subsequently
Botswana, were concerned, the intermittent presence of the Masubia on
the Island did not trouble anyone and was tolerated, not least because it
did not appear to be connected with interpretation of the terms of the
1890 Treaty.

75. The Court concludes from the foregoing that the peaceful and
public use of Kasikili/Sedudu Island, over a period of many years, by
Masubia tribesmen from the Eastern Caprivi does not constitute “subse-
quent practice in the application of the [1890] treaty” within the meaning
of Article 31, paragraph 3 (6), of the Vienna Convention on the Law of
Treaties.

*#

76. Botswana and Namibia also cite various other facts and incidents
from which they seek to derive evidence of subsequent practice by the
parties to the 1890 Treaty.

Thus Botswana asserts that Kasikili/Sedudu Island forms part of the
Chobe National Park established in 1967 and, before that, was part of
the Chobe Game Reserve created in 1960. According to Botswana, the
use of the international boundary as the northern limit of the Game
Reserve, and subsequently of the National Park, in the documents relat-
ing to their establishment necessarily had the effect of including Kasikili/
Sedudu Island within them.

Botswana also relies on an affidavit and report by a witness concerning
a visit to Kasane in 1972 by the then Botswana Head of State; from this
it seeks to imply that he may have visited the Island as well, while at the
same time acknowledging that there is no direct evidence that he actually
did so.

77. Namibia, for its part, places reliance on an incident occurring dur-
ing the same period. It states that three or four Caprivians were arrested
on the Island by Botswana game wardens for poaching and released by a
Botswana magistrate after a five-day detention, on the grounds that they
had been arrested outside Botswana’s jurisdiction. Namibia regards this
as an acknowledgment by a Botswanan official of Namibian sovereignty
over the Island.

54
1096 KASIKILI/SEDUDU ISLAND (JUDGMENT)

78. In the Court’s view, these additional facts and incidents cited by
the Parties cannot be regarded as representing “subsequent practice in
the application of the [1890] treaty which establishes the agreement of the
parties regarding its interpretation” (1969 Vienna Convention on the
Law of Treaties, Art. 31, para. 3 (b}).

The documents establishing the Chobe Game Reserve and the Chobe
National Park to which Botswana refers are internal documents, which,
moreover, contain no express reference to Kasikili/Sedudu Island.
Furthermore, Botswana itself recognizes that it has not been established
that the Botswana Head of State visited the Island in 1972. As regards
the incident cited by Namibia, it appears to be insufficiently proven.

*

79. The Court concludes from all of the foregoing that the subsequent
practice of the parties to the 1890 Treaty did not result in any “agreement
between the parties regarding the interpretation of the treaty or the
application of its provisions”, within the meaning of Article 31, para-
graph 3 (a), of the 1969 Vienna Convention on the Law of Treaties,
nor did it result in any “practice in the application of the treaty which
establishes the agreement of the parties regarding its interpretation”,
within the meaning of subparagraph (b) of that same provision.

80. However, the Court is bound to note that on at least three occa-
sions, at different periods — in 1912, in 1948 and in 1985 — surveys car-
ried out on the ground identified the channel of the Chobe to the north
and west as the “main channel” of the river around Kasikili/Sedudu
Island. The factual findings that the parties concerned arrived at sepa-
rately in 1948 were expressed in concurrent terms in a joint report. In
addition, the survey made in 1985 was conducted jointly by the parties
then concerned. The factual findings made on these occasions were not,
as such, disputed at the time. The Court finds that these facts, while not
constituting subsequent practice by the parties in the interpretation of the
1890 Treaty, nevertheless support the conclusions which it has reached by
interpreting Article III, paragraph 2, of the 1890 Treaty in accordance
with the ordinary meaning to be given to its terms (see paragraph 41
above).

+ * x

81. Both Parties have submitted in evidence in support of their respec-
tive positions a large number of maps, dating back as far as 1880. Most
of the early maps are of German origin (in particular, the maps of Seiner
(1909), Streitwolf (1910) and Frankenberg (1912)); there are, however,
others of British origin (such as the Bradshaw map (1880), the map
attached to the Eason Report (1912) and those contained in Colonial

55
1097 KASIKILI/SEDUDU ISLAND (JUDGMENT)

Office Reports published between 1912 and 1915). The more recent maps
include some prepared by the British (one of which, a map of Bechuana-
land compiled by the War Office in 1933, became the basis for several
subsequent maps), some produced by South Africa (including a 1949
map that served as an official map of the territory of South West Africa
until Namibian independence), some published by Botswana after inde-
pendence and one from the United Nations.

82. Namibia points out that the majority of the maps submitted in
these proceedings, even those emanating from British colonial sources
and intended to show the boundaries of Bechuanaland, tend to place the
boundary around Kasikili/Sedudu Island in the southern channel.
Namibia relies on this as “a specialized form of ‘subsequent practice’ and

. also an aspect both of the exercise of jurisdiction and the acquies-
cence in it that matures into prescriptive title”. Namibia places particular
weight in this respect on the 1933 War Office map entitled “Bechuana-
land Protectorate Sheet 2 1: 500,000 GSGS 3915”: it claims that this map
was in general use in Bechuanaland until 1965, and that, like other offi-
cial maps dating from the last three decades of British rule in Bechuana-
land, it excludes the Island from the territory of the Protectorate. Namibia
also relies in this regard on the Court’s decision in the Temple of Preah
Vihear case, where it was held that acceptance by the parties to a treaty
of a map showing a boundary may constitute an interpretation that
departs from the express terms of that treaty (Judgment of 15 June 1962
(Merits), C.J. Reports 1962, pp. 6 et seq.). Namibia then concludes:

“This substantially unbroken practice by all three of the parties
most closely concerned with the boundary between Botswana and
Namibia — Germany, Great Britain and South Africa — strongly
substantiates Namibia’s contention as to the proper interpretation of
Article IT (2) of the 1890 Treaty. At the same time, it lends signifi-
cant support to Namibia’s claim of sovereignty over the Island by
virtue of the doctrine of prescription and the principle of uti possi-
detis.”

83. Botswana for its part places less reliance on maps, pointing out,
inter alia, that most of the early maps show too little detail, or are too
small in scale, to be of value in this case. Botswana asserts, however, that
the available maps and sketches indicate that, from the time the Chobe
was surveyed with any particularity by European explorers from the
1860s onwards, a north channel around the Island was known and regu-
larly depicted. It cites the Bradshaw map of 1880, the Frankenberg map
of 1912 and Captain Eason’s map of 1912 as clearly indicating the pres-
ence of the northern and western channel in a manner closely similar to
its present configuration. Botswana does not, however, attempt to

56
1098 KASIKILI/SEDUDU ISLAND (JUDGMENT)

demonstrate that this places the boundary in the northern channel.
Rather, its overall position is that the map evidence is far less consistent
in placing the boundary in the southern channel than Namibia claims.
At the hearings, Botswana argued that, when accuracy, the precise
location of the boundary, and the fact of mere copying all are taken
into account, one is left with three maps showing the boundary in the
northern channel and only two in the southern channel (the 1933 British
GSGS 3915 map, and the 1949 South African map). Botswana further
asserts that there are technical problems with the latter two. As a conse-
quence, it disputes Namibia’s assertion that a preponderance of maps
show the boundary to be in the southern channel. In Botswana’s view,
the Court should look for a map that shows agreement of the Parties —
and that is to be found in the map attached to the Joint Survey of
1985 (see paragraph 64 above), which shows the boundary between
South Africa and Botswana to lie in the northern channel of the Chobe.

84. The Court will begin by recalling what the Chamber dealing with
the Frontier Dispute ( Burkina Fasol Republic of Mali) case had to say on
the evidentiary value of maps:

“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.” (LC. J. Reports 1986, p. 582, para. 54.)

As far as the present case is concerned, the Court notes that, according
to Article HI, paragraph 2, of the 1890 Treaty, “[t]he course of the...
boundary is traced in general accordance with a Map officially prepared
for the British Government in 1889”. No boundary line is drawn on this
map, and it was not annexed to the 1890 Treaty, although a slightly later
version of it was subsequently bound up with this Treaty in the British
Foreign Office archive, as being the map alluded to in Article III, para-
graph 2. There is also a map entitled “Map to Illustrate Article III of the
Anglo-German Agreement of I* July 1890”, published in 1909 in the
third edition of Hertslet’s Map of Africa by Treaty. While the Parties dif-

57
1099 KASIKILI/SEDUDU ISLAND (JUDGMENT)

fer in their view of the precise origin of this map, they apparently agree
that it does not depict any relevant information concerning the channels
around Kasikili/Sedudu Island or the location of the boundary. The
Court notes that there was no map appended to the 1890 Treaty officially
expressing the intentions of Germany and Great Britain with regard to
the course of the boundary between their respective possessions in the
area.

85. Certainly it is true, as the Court has already stated, that maps pub-
lished subsequently to the 1890 Treaty, in so far as they showed the
boundary at all, for a number of years placed it in the channel of the
Chobe passing to the south of the Island (this applies particularly to the
above-mentioned 1933 Bechuanaland map and 1949 South African map).
However, there was no indication that the placement of the boundary in
these maps was meant to be in accordance with Article III, paragraph 2,
of the 1890 Treaty; rather, its origins may be linked to the use of the
Island by the Masubia, which the Court has already rejected as evidence
of practice reflecting subsequent interpretation of Article III, para-
graph 2, by the parties to the 1890 Treaty (see paragraphs 74 and 75
above).

Moreover, once the issue of the boundary in the area had been raised
in 1947-1948, the local Caprivi and Bechuanaland officials agreed that
“the ‘main Channel’ d[id] not follow the waterway . . . usually shown on
maps as the boundary between the two Territories” (Trollope/Redman
Report, see paragraph 57 above). Those officials duly passed on their
views to their respective superiors, and the Court finds it not without rele-
vance in this regard that, in his letter of 26 January 1948 to the Bechua-
naland Government Secretary in Mafeking, Mr. Redman stated that
according to the 1890 Treaty the boundary must run along the northern
channel, and that the map showing the boundary in the southern channel
was “inaccurate and ... probably drawn by some-one who had not
examined the river to determine the main Channel” (see paragraph 58
above). It is clear from the subsequent correspondence between the South
African and Bechuanaland authorities (see paragraphs 59 and 60 above)
that their differing positions on the status of Kasikili Island and the loca-
tion of the boundary had by 1951 hardened to the point where a local de
facto arrangement became necessary. The Court considers that, in the
light of that disagreement, there cannot be any question of the authorities
concerned having accepted the maps then available in a manner capable
of constituting “subsequent practice in the application of the [1890]
treaty”, still less recognition of the boundary shown on those maps. To
the contrary, it appears to the Court that the parties largely ignored the
maps, which they regarded as either accurate or inaccurate according to
their respective positions on the course of the boundary.

58
1100 KASIKILI/SEDUDU ISLAND (JUDGMENT)

86. After Botswana’s accession to independence, the relevant carto-
graphic material shows greater variation, with certain maps (for example,
the 1974 Botswana 1:50,000 map, the 1978 and 1982 official maps of the
South African Ministry of Defence (JARIC) 1: 100,000, the 1984 South
Africa 1:50,000 map (the military intelligence version used by the South
African army, with red overprint) and the 1984 Botswana 1 : 50,000 map)
from then on placing the boundary around Kasikili/Sedudu Island in the
Chobe’s northern channel.

The Court will recall that this position was noted in the introduction to
the 1985 Joint Survey Report and that the Botswana and South African
experts concluded in this regard that “[t]he disparity in the depiction of
the boundary between South African maps and those of Botswana ha[d]
probably been a contributory factor in the recent border incident near
Kasane” (see paragraph 64 above). The persistent uncertainty about the
course of the boundary in the region — which led to the decision to
undertake the 1985 Joint Survey — and the inconsistencies between maps
preclude, in the Court’s view, the possibility of there having been any
kind of agreement, whether by way of interpretation of the 1890 Treaty
or on any other basis, concerning the validity of any boundary depicted.
The same is true of the subsequent period, when the dispute between Bot-
swana and the newly independent Namibia crystallized.

87. In view of the absence of any map officially reflecting the inten-
tions of the parties to the 1890 Treaty and of any express or tacit agree-
ment between them or their successors concerning the validity of the
boundary depicted in a map (cf. Temple of Preah Vihear, Judgment,
Merits, LC.J. Reports 1962, pp. 33-35), and in the light of the uncer-
tainty and inconsistency of the cartographic material submitted to it, the
Court considers itself unable to draw conclusions from the map evidence
produced in this case. That evidence cannot therefore “endorsle] a con-
clusion at which a court has arrived by other means unconnected with the
maps” (Frontier Dispute ( Burkina Fasol Republic of Mali), L C.J. Reports
1986, p. 583, para. 56), nor can it alter the results of the Court’s textual
interpretation of the 1890 Treaty.

88. The foregoing interpretation of the relevant provisions of the 1890
Treaty leads the Court to conclude that the boundary between Botswana
and Namibia around Kasikili/Sedudu Island provided for in this Treaty
lies in the northern channel of the Chobe River.

89. According to the English text of the Treaty, this boundary follows
the “centre” of the main channel; the German text uses the word “thal-
weg”. The Court has already indicated that the parties to the 1890 Treaty
intended these terms to be synonymous and that Botswana and Namibia

59
1101 KASIKILYSEDUDU ISLAND (JUDGMENT)

had not themselves expressed any real difference of opinion on this sub-
ject (see paragraph 25 above).

It is moreover clear from the travaux préparatoires of the Treaty (see
paragraph 46 above) that there was an expectation of navigation on the
Chobe by both contracting parties, and a common intention to exploit
this possibility. Although, as has been explained above, the parties in
1890 used the terms “thalweg” and “centre of the channel” interchange-
ably, the former reflects more accurately the common intention to exploit
navigation than does the latter. Accordingly, this is the term that the
Court will consider determinative in Article III, paragraph 2.

Inasmuch as Botswana and Namibia agreed, in their replies to a ques-
tion put by a Member of the Court, that the thalweg was formed by the
line of deepest soundings, the Court concludes that the boundary follows
that line in the northern channel around Kasikili/Sedudu Island.

x * %
90. Namibia, however, claims title to Kasikili/Sedudu Island, not only
on the basis of the 1890 Treaty but also, in the alternative, on the basis of
the doctrine of prescription. Namibia argues that

“by virtue of continuous and exclusive occupation and use of Kasi-
kili Island and exercise of sovereign jurisdiction over it from the
beginning of the century, with full knowledge, acceptance and
acquiescence by the governing authorities in Bechuanaland and
Botswana, Namibia has prescriptive title to the Island”.

91. Botswana maintains that the Court cannot take into consideration
Namibia’s arguments relating to prescription and acquiescence as these are
not included in the scope of the question submitted to it under the terms of
the Special Agreement. According to Botswana, the purpose of that Agree-
ment was to obtain from the Court determination of the boundary solely
on the basis of the 1890 Treaty; invoking prescription would therefore
involve adopting a totally different basis for determining the boundary. In
support of its argument, Botswana points out in particular that the refer-
ence in the Special Agreement to the “rules and principles of international
law” is “pleonastic”, since an international agreement is normally inter-
preted taking into account any relevant rules of international law appli-
cable in the relations between the parties. And it adds that:

“the alleged evidence of prescriptive title cannot be accepted as ‘sub-
sequent practice’, because in such a hypothesis the working assump-
tion ts precisely the existence of a title of Botswana (or its pre-
decessor) which allegedly is displaced by the operation of prescrip-
tion”.

60
1102 KASIKILI/SEDUDU ISLAND (JUDGMENT)

92. Namibia disputes this argument. It claims, for its part, that the
wording of the question in the Special Agreement is clear and

“requires the Court to consider any evidence or submissions of the
parties grounded in general rules and principles of international law
equally with submissions based on the 1890 Treaty”

According to Namibia,

“Botswana’s attempt to treat the reference to the ‘rules and prin-
ciples of international law’ as if it were not included in the Special
Agreement contravenes fundamental rules of treaty interpretation.”

It stresses the contradictory nature of the position taken by Botswana,
which, on the one hand, suggests that the expression “rules and principles
of international law” covers only the rules and principles concerning
treaty interpretation and, on the other, itself acknowledges that interna-
tional law rules concerning treaty interpretation are comprehended in the
first clause of the question referring to the 1890 Treaty. Namibia also
reproaches Botswana for ignoring the dual nature of the argument it has
put forward that

“either the subsequent conduct operates as a ‘practice . . . which
establishes the agreement of the parties regarding [the] interpreta-
tion’ of the Treaty; or it stands as an independent root of title based
on the doctrine of prescription and/or acquiescence”.

93. The Court notes that under the terms of Article I of the Special
Agreement, it is asked to determine the boundary between Namibia and
Botswana around Kasikili/Sedudu Island and the legal status of the
Island “on the basis of the Anglo-German Treaty of 1 July 1890 and the
rules and principles of international law”. Even if there had been no ref-
erence to the “rules and principles of international law”, the Court would
in any event have been entitled to apply the general rules of international
treaty interpretation for the purposes of interpreting the 1890 Treaty. It
can therefore be assumed that the reference expressly made, in this provi-
sion, to the “rules and principles of international law”, if it is to be mean-
ingful, signifies something else. In fact, the Court observes that the
expression in question is very general and, if interpreted in its normal
sense, could not refer solely to the rules and principles of treaty interpre-
tation. The restrictive interpretation of this wording espoused by Bot-
swana appears to be even less well-founded, in that Article III of the
Special Agreement specifies that “[t]he rules and principles of interna-
tional law applicable to the dispute shail be those set forth in the provi-
sions of Article 38, paragraph 1, of the Statute of the International Court
of Justice”. This wording shows that the Parties had no intention of con-
fining the rules and principles of law applicable in this case solely to the
rules and principles of international law relating to treaty interpretation.

61
1103 KASIKILI/SEDUDU ISLAND (JUDGMENT)

In the Court’s view the Special Agreement, in referring to the “rules
and principles of international law”, not only authorizes the Court to
interpret the 1890 Treaty in the light of those rules and principles but also
to apply those rules and principles independently. The Court therefore
considers that the Special Agreement does not preclude the Court from
examining arguments relating to prescription put forward by Namibia.

94. According to Namibia, four conditions must be fulfilled to enable
possession by a State to mature into a prescriptive title:

“1. The possession of the . .. state must be exercised à titre de sou-
verain,
2. The possession must be peaceful and uninterrupted.
3. The possession must be public.
4. The possession must endure for a certain length of time.”

Namibia alleges that in the present case Germany was in peaceful pos-
session of the Island from before the beginning of the century and exer-
cised sovereignty over it from the time of the establishment of the first
colonial station in the Caprivi in 1909, all in full view and with the full
knowledge of the Bechuanaland authorities at Kasane, only a kilometre
or two from the Island. It states that this peaceful and public possession
of the Island, à titre de souverain, was continued without interruption by
Germany’s successor until accession of the territory to independence.
Finally, it notes that, after itself becoming independent in 1966, Bot-
swana, which was aware of the facts, remained silent for almost two
further decades.

In support of its allegations, Namibia emphasizes the importance of
the presence on the Island of Masubia people from the Eastern Caprivi
“from the beginning of the colonial period at least, and probably a good
deal further back than that”. It asserts that

“[clolonial records of German, British and South African authorities
and the testimony of members of the Masubia community in the
Kasika district before the JTTE [Joint Team of Technical Experts]
{in 1994] conclusively show that the Masubia people of Eastern
Caprivi have occupied and used Kasikili Island since time immemo-
rial”
and points out that “[t]he Masubia of the Caprivi Strip have used and
occupied Kasikili Island as a part of their lands and their lives”. Although
Namibia admits that, in order to establish sovereignty by operation of
prescription, acquiescence and recognition, it must show more than the
use of the disputed territory by private individuals for their private ends,
it maintains that:

“Namibia’s predecessors exercised continuous authority and juris-
diction over Kasikili Island. From 1909 until the termination of the
Mandate in 1966, German, Bechuanaland and South African offi-
cials consistently governed the Eastern Caprivi through Masubia
chiefs, whose jurisdiction extended to Kasikili Island. After termina-

62
1104 KASIKILI/SEDUDU ISLAND (JUDGMENT)

tion of the Mandate, South Africa, under pressure from the libera-
tion struggle, increasingly exerted direct power in the area until
Namibia’s independence on 21 March 1990.”

Namibia states that the authority exercised over Kasikili Island by its
predecessors was implemented

“(flor the most part . . . through the modality of ‘indirect rule,’ using
the chiefs and political institutions of the Masubia to carry out the
directives of the ruling power, under the control and supervision of
officials of that power”

and that

“[allthough indirect rule was manifested in a variety of ways, its
essence was that the acts of administration of the colonial authorities
and those of the traditional authorities were acts of a single entity:
the colonial government”.

According to Namibia, this situation

“prevailed without any objection, reservation or protest from Bot-
swana or its predecessors in interest for almost a century until 1984,
when Botswana first made formal claim to the Island in private
meetings with the South African government”.

In support of its argument concerning prescription, Namibia also
invokes the incident between a patrol boat of the South African Defence
Force and a unit of the Botswana Defence Force in October 1984, which,
in its view, indicated that South Africa was exercising jurisdiction over
the Island by conducting military patrols in the southern channel. It also
refers to a number of official maps of the Caprivi portraying the Island as
part of Namibia from the beginning of the century, as well as to the con-
currence of the British authorities.

95. Although it considers the doctrine of prescription inapplicable in
this case for the reasons referred to earlier, Botswana accepts the criteria
for acquiring prescriptive title as set out by Namibia; it argues, however,
that those criteria have not been satisfied by Namibia and its predeces-
sors. Botswana asserts, in substance, that “there is no credible evidence
that either Namibia or its predecessors exercised State authority in respect
of Kasikili/Sedudu” and that even if peaceful, public and continuous
possession of the Island by the people of Caprivi had been proved, it
could not have been à titre de souverain.

Botswana does not dispute that people from the Caprivi used Kasikili/
Sedudu Island at times for agricultural purposes; but it maintains that so
did people living on the other side of the Chobe, in Bechuanaland, and

63
1105 KASIKILIWSEDUDU ISLAND (JUDGMENT)

denies that there was ever any village or permanent settlement on the
Island. Botswana emphasizes that in any case “[t]he acts of private per-
sons cannot generate title unless those acts are subsequently ratified by
the State”; that no evidence has been offered to the effect that the Masu-
bia chiefs had authority to engage in title-generating activities for the
benefit of Germany or its successors; and that evidence is also lacking of
any “genuine belief” in the existence of title on the part of Germany and
its successors.

With regard to patrolling by South Africa, Botswana asserts that this
involved at the very most anti-guerilla operations, which cannot be classi-
fied as an exercise of jurisdiction; it claims that the incident of 1984
could not constitute evidence of peaceful possession for the purposes of
prescription. Finally, Botswana denies that the map evidence has any
value in this case; it maintains that this evidence is contradictory and
confused and that the authorities of Bechuanaland and Botswana
never recognized or acquiesced in the maps showing the boundary in the
southern channel.

96. The Parties agree between themselves that acquisitive prescription
is recognized in international law and they further agree on the condi-
tions under which title to territory may be acquired by prescription, but
their views differ on whether those conditions are satisfied in this case.
Their disagreement relates primarily to the legal inferences which may be
drawn from the presence on Kasikili/Sedudu Island of the Masubia of
Eastern Caprivi: while Namibia bases its argument primarily on that
presence, considered in the light of the concept of “indirect rule”, to
claim that its predecessors exercised title-generating State authority over
the Island, Botswana sees this as simply a “private” activity, without any
relevance in the eyes of international law.

97. For present purposes, the Court need not concern itself with the
status of acquisitive prescription in international law or with the condi-
tions for acquiring title to territory by prescription. It considers, for the
reasons set out below, that the conditions cited by Namibia itself are not
satisfied in this case and that Namibia’s argument on acquisitive prescrip-
tion therefore cannot be accepted.

98. The Court has already considered the presence of the Masubia on
Kasikili/Sedudu Island when it examined the subsequent practice of the
parties to the 1890 Treaty (see paragraphs 71 ef seg. above).

It follows from this examination that even if links of allegiance may
have existed between the Masubia and the Caprivi authorities, it has not
been established that the members of this tribe occupied the Island à titre
de souverain, i.e., that they were exercising functions of State authority
there on behalf of those authorities. Indeed, the evidence shows that the
Masubia used the Island intermittently, according to the seasons and

64
1106 KASIKILI/SEDUDU ISLAND (JUDGMENT)

their needs, for exclusively agricultural purposes; this use, which began
prior to the establishment of any colonial administration in the Caprivi
Strip, seems to have subsequently continued without being linked to ter-
ritorial claims on the part of the Authority administering the Caprivi.
Admittedly, when, in 1947-1948, the question of the boundary in the
region arose for the first time between the local authorities of Bechuana-
land Protectorate and of South Africa, the Chobe’s “main channel”
around the Island was said to be the northern channel, but the South
African authorities relied on the presence of the Masubia on the Island in
order to maintain that they had title based on prescription. However,
from then on the Bechuanaland authorities took the position that the
boundary was located in the northern channel and that the Island was
part of the Protectorate; after some hesitation, they declined to satisfy
South Africa’s claims to the Island, while at the same time recognizing
the need to protect the interests of the Caprivi tribes. The Court infers
from this, first, that for Bechuanaland, the activities of the Masubia on
the Island were an independent issue from that of title to the Island and,
second, that, as soon as South Africa officially claimed title, Bechuana-
land did not accept that claim, which precluded acquiescence on its part.

99. In the Court’s view, Namibia has not established with the neces-
sary degree of precision and certainty that acts of State authority capable
of providing alternative justification for prescriptive title, in accordance
with the conditions set out by Namibia, were carried out by its predeces-
sors or by itself with regard to Kasikili/Sedudu Island. The Court has
already observed above that it is unable to draw conclusions from the
map evidence produced in this case (see paragraph 87 above). Nor in its
view, can conclusions be drawn from the incident involving Botswana
and South African defence forces in the channel to the south of the
Island in October 1984.

* * *

100. The Court’s interpretation of Article III, paragraph 2, of the 1890
Treaty has led it to conclude that the boundary between Botswana and
Namibia around Kasikili/Sedudu Island follows the line of deepest sound-
ings in the northern channel of the Chobe.

101. Since the Court has not accepted Namibia’s argument on pre-
scription, it follows for this reason also that Kasikili/Sedudu Island forms
part of the territory of Botswana.

102. The Court observes, however, that the Kasane Communiqué of
24 May 1992 records that the Presidents of Namibia and Botswana
agreed and resolved that:

“{c) existing social interaction between the people of Namibia and
Botswana should continue;
(d) the economic activities such as fishing shall continue on the
understanding that fishing nets should not be laid across the
river ;

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(e) navigation should remain unimpeded including free movement
of tourists”.

The Court further observes that in explanation and in pursuance of the
foregoing agreement, Botswana stated at the oral hearings:

“Botswana’s policy is to allow free navigation, including un-
impeded movement of tourist boats even in the southern channel.
This policy applies to boats owned by Namibian tourist operators
as well. The only requirement is that all tourist boats should be
registered. This requirement is meant solely to prevent the danger
of environmental pollution of the Chobe River. Experience has
shown that some tourist boat operators tended to transport their
boats from Okavango waters, infested with river weeds, down to
the Chobe River, without applying for a trans-zonal permit. The
Department of Water Affairs, and not the Botswana Defence Force,
is responsible for enforcing the policy on anti-pollution of the river
waters.

Botswana’s policy on free navigation, including the free move-
ment of tourist boats, was set out in paragraph (e) of the Kasane
Communiqué . . . Since the Kasane Communiqué was agreed in May
1992, there has been no complaint from the Namibian Government
that Botswana ever breached paragraph (e) of the Communiqué
which guarantees unimpeded navigation.”

Subsequently, Botswana added that:

“Botswana also wishes to reiterate that tourist boats from Namibia
are free to travel in the southern channel. The only requirement is
that all such boats should be registered, in order to control noxious
aquatic weeds . . . this requirement is backed by proper legislation,
namely, the Laws of Botswana Aquatic Weeds (Control) Act, which
commenced in December 1971. The provisions of this Act were later
discussed with, and endorsed by the Water Affairs Department of
Namibia. Since then, Namibian tourist boat operators have regis-
tered as many as 53 boats, to travel in Botswanan waters of the
Chobe River. These 53 Namibian boats are permitted to navigate in
the southern channel, like any others that have been licensed.”

103. The Court, which by the terms of the Joint Agreement between
the Parties is empowered to determine the legal status of Kasikili/Sedudu
Island concludes, in the light of the above-mentioned provisions of the
Kasane Communiqué, and in particular of its subparagraph (e) and the
interpretation of that subparagraph given before it in this case, that the
Parties have undertaken to one another that there shall be unimpeded

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navigation for craft of their nationals and flags in the channels of
Kasikili/Sedudu Island. As a result, in the southern channel of Kasikili/
Sedudu Island, the nationals of Namibia, and vessels flying its flag, are
entitled to, and shall enjoy, a treatment equal to that accorded by Bot-
swana to its own nationals and to vessels flying its own flag. Nationals of
the two States, and vessels, whether flying the flag of Botswana or of
Namibia, shall be subject to the same conditions as regards navigation
and environmental protection. In the northern channel, each Party shall
likewise accord the nationals of, and vessels flying the flag of, the other,
equal national treatment.

104. For these reasons,
THE Court,

(1) By eleven votes to four,

Finds that the boundary between the Republic of Botswana and
the Republic of Namibia follows the line of deepest soundings in the
northern channel of the Chobe River around Kasikili/Sedudu Island;

IN FAVOUR: President Schwebel; Judges Oda, Bedjaoui, Guillaume, Ranjeva,
Herczegh, Shi, Koroma, Vereshchetin, Higgins, Kooijmans;

AGAINST: Vice-President Weeramantry; Judges Fleischhauer, Parra-
Aranguren, Rezek.

(2) By eleven votes to four,

Finds that Kasikili/Sedudu Island forms part of the territory of the
Republic of Botswana;

IN FAVOUR: President Schwebel; Judges Oda, Bedjaoui, Guillaume, Ranjeva,
Herczegh, Shi, Koroma, Vereshchetin, Higgins, Kooijmans;
AGAINST: Vice-President Weeramantry; Judges Fleischhauer, Parra-

Aranguren, Rezek.
(3) Unanimously,

Finds that, in the two channels around Kasikili/Sedudu Island, the
nationals of, and vessels flying the flags of, the Republic of Botswana and
the Republic of Namibia shall enjoy equal national treatment.

Done in English and in French, the English text being authoritative,
at the Peace Palace, The Hague, this thirteenth day of December,
one thousand nine hundred and ninety-nine, in three copies, one of which

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will be placed in the archives of the Court and the others transmitted to
the Government of the Republic of Botswana and the Government of the

Republic of Namibia, respectively.
(Signed) Stephen M. SCHWEBEL,
President.

(Signed) Eduardo VALENCIA-OSPINA,
Registrar.

Judges RANJEVA, Koroma and HIGGINS append declarations to the
Judgment of the Court.

Judges ODA and KooïMaNs append separate opinions to the Judgment
of the Court.

Vice-President WEERAMANTRY, Judges FLEISCHHAUER, PARRA-
ARANGUREN and REZEK append dissenting opinions to the Judgment of
the Court.

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

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