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| I. | Substantive International Law - First Part |
| 7. | LAW OF TREATIES |
| 7.8. | Interpretation |
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Kasikili/Sedudu Island
(Botswana/Namibia)
Judgment of 13 December 1999
[pp. ] 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 binding 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 Jamahiriya/Chad), Judgment, I.C.J. Reports 1994, p. 21, para. 41; Oil Platforms (Islamic Republic of Iran v. United States of America), Preliminary Objections, Judgment, I.C.J. Reports 1996 (II), 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.
[p. ] 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 Jamahiriya/Chad), Judgment, I.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 (Argentina/Chile) [Dispute concerning the course of the frontier between B.P. 62 and Mount Fitzroy (Argentina/Chile)], 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 international public (RGDIP), Vol. 2, 1996, p. 592, para. 157).
[p. ] 55. The Court shares the view that the Eason Report and its surrounding circumstances cannot be regarded as representing "subsequent practice 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, moreover, 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).
[pp. ] 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, "[a]fter separate examination of the terrain and the examination 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 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 unfounded 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 demonstrating 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 [of 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)).
[pp. ] 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 - constitute an "intergovernmental agreement ... between the parties regarding ... 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 international law do[es] not require any particular formality for the conclusion 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".
Namibia categorically denies that the discussions conducted between the Botswana and South African authorities in 1984-1985 led to an agreement on the boundary; it stresses in this connection that the July 1985 joint survey was not "self-executing" and was devoid of any legally binding 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 territory.
68. Having examined the documents referred to above, the Court cannot 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 conclusions; not only did South Africa fail to accept them but on several occasions 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 competence to conclude such an agreement, since at that time the United Nations General Assembly had already terminated South Africa's Mandate 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) notwithstanding 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 administration from Namibia immediately and thus put an end to its occupation of the Territory;
(2) ... States Members of the United Nations are under obligation 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" (I.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.
[pp. ] 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 interpretation" (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 intermittent presence on the Island of people from the Caprivi Strip. However, 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 Bechuanaland Protectorate in the area in question, Captain Eason of the Bechuanaland police stated that "the North should be claimed as the main channel" 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 German territory [we]re ... growing crops on it" (see paragraph 53 above). There were similar statements in the Trollope-Redman Report of 19 January 1948, in which the two officials expressed the view that "the 'main channel' lies in the waterway which would include the island in question in the Bechuanaland Protectorate"; at the same time, they noted that "use ha[d] 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 "[l]ivestock 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 "subsequent practice in the application of the [1890] treaty" within the meaning of Article 31, paragraph 3 (b), 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.
[pp. ] 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 relating 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 during 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.
78. In the Courts 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.
[pp. ] 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, paragraph 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 occasions, at different periods - in 1912, in 1948 and in 1985 - surveys carried 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 separately 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).
[p. ....] 87. In view of the absence of any map officially reflecting the intentions of the parties to the 1890 Treaty and of any express or tacit agreement between them or their successors concerning the validity of the boundary depicted in a map (cf. Temple of Preah Vihear, Judgment, Merits, I.C.J Reports 1962, pp. 33-35), and in the light of the uncertainty 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 "endors[e] a conclusion at which a court has arrived by other means unconnected with the maps" (Frontier Dispute (Burkina Faso/Republic of Mali), I.C.J. Reports 1986, p. 583, para. 56), nor can it alter the results of the Court's textual interpretation of the 1890 Treaty.
[p. Decl. Higgins] 2. The term "the main channel" is not a "generic term" (cf. Aegean Sea Continental Shelf case, I.C.J. Reports 1978, para. 77) - that is to say, a known legal term, whose content the Parties expected would change through time. Rather, we find ourselves closer to the situation of the Arbitral Tribunal in the Laguna del Desierto case of 1994 (see para. 20 of the Court's Judgment). The Tribunal there stated that it could not accept Chile's argument:
"that to apply the 1902 Award in light of geographical knowledge acquired subsequently would be equivalent to its revision through the retrospective consideration of new facts. The 1902 Award defined, in the sector with which this Arbitration is concerned, a frontier which follows a natural feature that, as such, does not depend on accurate knowledge of the area but on its true configuration. The ground remains as it has always been ... [t]his Judgment is ... faithfully applying the provisions of the Award of 1902." (International Law Reports, Vol. 113, p. 76, para. 157.)
This dictum retains a certain relevance, notwithstanding that the fact situation in the Laguna case is somewhat different from ours.
3. The Court is indeed, for this particular task, entitled to look at all the criteria the Parties have suggested as relevant. This is not to discover a mythical "ordinary meaning" within the Treaty, but rather because the general terminology chosen long ago falls to be decided today. To use contemporary knowledge and scientific data to assist in fulfilling that task is not at all inconsistent with the intertemporal rule in the Island of Palmas Award, which was concerned with the legal rules applicable to title to territory and not with identification, through the legal technique of evaluating evidence, of a chosen term.
4. At the same time, we must never lose sight of the fact that we are seeking to give flesh to the intention of the Parties, expression in generalized terms in 1890. We must trace a thread back to this point of departure. We should not, as the Court appears at times to be doing, decide what in abstracto the term "the main channel" might today mean, by a mechanistic appreciation of relevant indicia. Rather, our task is to decide what general idea the Parties had in mind, and then make reality of that general idea through the use of contemporary knowledge.
[p. S.O. Oda] 4. ... It appears to me that the Judgment places excessive reliance upon the Vienna Convention on the Law of Treaties for the purpose of the Court's interpretation of the 1890 Anglo-German Treaty. The Parties to this case certainly agreed that the Court should be asked to determine the boundary on the basis of the 1890 Treaty - and it should again be pointed out quite categorically that Botswana and Namibia are not parties to that Treaty - but the Court has not been asked to interpret the 1890 Treaty itself. The Judgment quotes Article 31 (General rule of interpretation) of the 1969 Vienna Convention on the Law of Treaties almost in its entirety. Reference is made in the Judgment to this provision of the Vienna Convention at least eleven times. Although I am fully aware that the Vienna Convention reflects customary international law, it should, however, be noted, as the Judgment correctly points out in its paragraph 18, that this Convention "applies only to treaties which are concluded by States after the entry into force of the present Convention with regard to such States" (Art. 4). In fact, the Convention came into force in 1980. This case does not appear to me to be one related to the application of the Vienna Convention.
[p. S.O. Oda] 7. The Judgment refers to various acts or conduct relating to the Chobe River and to certain survey reports concerning the River produced by various authorities. I accept that these facts and the survey reports are extremely important for the Court's consideration of the matter. However, I am unable to accept the Courts position that such facts and reports could be considered only as possible evidence of "any subsequent agreement between the parties regarding the interpretation of the treaty or the application of its provisions" or "any subsequent practice in the application of the treaty which establishes the agreement of the parties regarding its interpretation" within the meaning of Article 31, paragraph 3, of the Vienna Convention on the Law of Treaties, to be taken into account when interpreting the 1890 Anglo-German Treaty. The Court, after a lengthy analysis (paras. 47 to 70), comes to the conclusion that the facts and documents in question cannot be regarded as constituting "any subsequent agreement" or "any subsequent practice" to be used for the interpretation of the 1890 Treaty, although the Court ultimately found that these facts "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" (para. 80). I would rather suggest that these facts and documents should be considered at their face value, as historical background to the present case but without having any bearing on the provisions of the Vienna Convention, in order to assist the Court in determining the boundary.
[p. S.O. Oda] 59. After an examination of certain incidents that occurred in the area, as well as the correspondence between the authorities of the northern bank and southern bank and certain surveys conducted in the course of the past hundred years, I conclude that the northern channel of the Chobe River had been regarded, implicitly or explicitly, as the boundary separating the authorities on the northern and southern banks, and that Kasikili/Sedudu Island had been regarded as being under the authority of the south, despite the occasional use of the Island by tribespeople from the northern side.
The Judgment, however, refers to these same past practices as if they might serve to assist it in interpreting the 1890 Anglo-German Treaty as provided for in the Vienna Convention on the Law of Treaties, and the Court came to the conclusion that those practices were not in fact capable of constituting "subsequent practice" or "subsequent agreement" within the meaning of the Vienna Convention. I would emphasize once more that in my view this case is not one directly related to the application of the provisions of the Vienna Convention on the Law of Treaties to the 1890 Anglo-German Treaty, to which later Treaty neither Botswana nor Namibia is a party.
I refer above to these past practices, as decisive factors in assisting the Court to determine the course of the boundary in the Chobe River and, hence, to determine the status of Kasikili/Sedudu Island as a part of the territory of Botswana.
[p. D.O. Weeramantry] 26. For the purposes of the case before us, the words "any subsequent agreement" seem to me to refer to any consensus or common understanding in regard to how the words in question are to be viewed. The word "agreement" here is not restricted to a subsequent agreement in the sense of a fresh verbal agreement superimposed upon the original. It also embraces a consensus or common understanding, as shown by conduct, regarding its interpretation or application. Such conduct can take the form of action or inaction, affirmation or silence. I uphold the Namibian contention in this regard, and do not think it waters down the meaning of the term "agreement", as Botswana contends.
[p. D.O. Weeramantry] 29. We are not here interpreting or applying a legal concept, in which case intertemporal principles might, in certain cases, attract the meaning that concept bears at the time of interpretation. Rather, we are here examining a question of fact as to which of the two channels was considered by the Parties at that time to be the main channel. This principle of contemporaneity is one of the important principles of treaty interpretation, and is not, I think, given its proper effect by taking into account, as the Court has done, the attitude of the Parties more than 50 years later, when political and other circumstances may well have necessitated a change of administrative policy from that which had been evidenced for the half century immediately following the Treaty.
[p. D.O. Weeramantry] 35. ... I believe there is no dispute regarding Masubian cultivation of the Island until 1947, allowing for such occasional intervals as were necessitated by climatic conditions. I believe the evidence supports the view that, from 1890 to 1947, such cultivation during the period when the Island was not flooded was a regular feature.
36. Colonial governments depended heavily on chiefly authority at a local level, and the claims and movements of chieftains were not matters of indifference to them.
What do we infer from this?
This may not have been occupation by a sovereign government such as is necessary for the acquisition of title by adverse prescription, though it could come close to such an interpretation. However, it was an occupation of the land of which the administrations on both sides were not unaware. If this occupation was in disregard of the 1890 Treaty, one would have expected the Government of Botswana or its predecessors to lodge a protest, or at least to make it clear that the Masubia were there on sufferance. There is no evidence of any such action on Botswana's part.
[p. D.O. Fleischhauer] In its effort to establish an ordinary meaning of the term to be interpreted, on which the Court could proceed, the Judgment is not fully consonant with the system of interpretation provided for by the Vienna Convention. It discusses only certain aspects of the object and purpose of the 1890 Treaty and does not deal at all with the context in which the term "main channel of that river"/"Hauptlauf dieses Flusses" is used in that Treaty (Judgment, paras. 43-45). Object and purpose of the Treaty in which the term to be interpreted finds itself and the context in which the term has been used, are important elements of treaty interpretation as they throw light on the intentions of the Parties which are a key factor for treaty interpretation as foreseen by the Vienna Convention. An interpretation of the term "main channel of that river"/"Hauptlauf dieses Flusses", which properly takes into account the object and purpose of the Treaty and the context in which this term is used in Article III (2), leads to a result that is different from the one reached by the Court in its Judgment.
[p. D.O. Fleischhauer] 5. As to object and purpose of the 1890 Treaty, I would like to first observe that the 1890 Treaty is a bilateral treaty and that, as is often the case with bilateral treaties, object and purpose pursued with the Treaty by its parties follow fairly clearly from its text. The object of the 1890 Treaty were the spheres of influence of the two contracting parties in Africa and the purpose was their agreed delimitation (Arts. I-IV of the Treaty) in order to secure the respect by each of the parties of the sphere of the other (Art. VII). Although the delimitations provided for in the Treaty have evolved to become existing boundaries between African States, including the boundary between Namibia and Botswana, the Treaty has not to be regarded as a boundary treaty in the technical sense; the Treaty was meant to keep the political relations between the two contracting States undisturbed by rivalry in Africa. This cannot be overlooked in its interpretation; the Treaty must not be understood as meaning a comprehensive settlement of all questions regarding the actual course of the delimitations it establishes. It seems quite compatible with the Treaty's object and purpose that, in certain places, it sets forth only in broad lines where the delimitation of the spheres of interests runs but leaves the fixation of its course in detail to the future application of the Treaty.
[p. D.O. Fleischhauer] 9. In placing hopes in the expected navigational use of the Chobe River, the parties were in error; the context in which they perceived the "main channel of that river"/"Hauptlauf dieses Flusses" was unreal. We know now, more than hundred years after the conclusion of the Treaty, that the river has not been used, and is not usable, for larger-scale navigation. This is mainly due to the fact that if there was a fully navigable part of the Chobe, it would run from nowhere to nowhere, i.e., from some point upstream from Kasikili/Sedudu Island to the point where - downstream from the Island - the Mambova Rapids block navigation. But also the particular hydrological conditions prevailing in the Chobe in the area around Kasikili/Sedudu Island would not permit full navigational use of the river there. This is supported by the fact that while an attempt at lumber floating was undertaken by Mr. Ker in 1947-1948, the Court has not been informed that this attempt was repeated after Mr. Ker's first experience. The Zambezi Queen is not operated on a regular schedule but is moored in the northern channel as a floating hotel. The only navigational activity which has ever, in a sustained way, been carried out on the River Chobe, is the operation of the tourist flatboats that has taken place, for some time now, mainly in the southern channel, as the Island is becoming known as a major wildlife feeding ground readily accessible to safe viewing by tourists who mainly come from Botswana. The parties to the Treaty were thus in error when they drafted the Treaty in the expectation of larger-scale navigational usability of the Chobe, in particular in giving access to the Zambezi.
The error with which the Court is confronted here is not an error "in a treaty" as dealt with by Article 48 of the Vienna Convention on the Law of Treaties, which one State party to the treaty wishes to invoke "as invalidating its consent to be bound by the treaty". It is rather an error in motivation which led to the use of the term "main channel of that river"/"Hauptlauf dieses Flusses" in Article III (2) of the 1890 Treaty, an error made by both parties to the Treaty. The question that arises does not concern the validity of the consent to be bound by the Treaty; the error rather raises the question whether a mistaken expectation of the parties when they drew up the Treaty can still serve, more than 100 years after the conclusion of the Treaty and a long time after the error has become clear, in the interpretation of the Treaty.
In the circumstances of the present case, the interpretation of the term "main channel"/"Hauptlauf dieses Flusses" based on the mistaken expectation of large-scale navigational usability of the Chobe cannot be held against Namibia because that would mean that Namibia alone would be burdened with the consequences of the error. The flatboat navigation connected to the tourist activities that have evolved on and around Kasikili/Sedudu Island is concentrated in the southern channel. Interpretation of the term "the main channel of that river"/"Hauptlauf dieses Flusses" in favour of the northern channel would deprive Namibia from having an equitable share in the only navigational use of the Chobe there is to share. That would run directly counter to the intention of the parties to split the river evenly. Therefore the interpretation of the term "main channel of that river"/"Hauptlauf dieses Flusses" in favour of the northern channel would not be compatible with the principle of good faith which, according to Article 31, paragraph 1, of the Vienna Convention, governs all treaty interpretation. Interpretation of the term "main channel of that river"/"Hauptlauf dieses Flusses" in favour of the southern channel, however, would correspond to what the parties wanted to achieve regarding the River Chobe. It would be a good faith interpretation of the term because it would split evenly between the Parties the only channel that is of some navigational interest.
[pp. D.O. Parra-Anguren] 42. Consequently, after the confirmation of the creation of the mandate by the Council of the League of Nations in 1920, the Union of South Africa could not dispose by its own actions of the territory of South West Africa, as it had been determined by the subsequent practice of the parties to the 1890 Anglo-German Agreement.
43. For this reason, 1914 is the latest date to be taken into account for the determination of the subsequent practice of the parties, Germany and Great Britain, in regard to the interpretation of Article III of the 1890 Anglo-German Agreement. In fact, no subsequent practice could exist on the part of Germany after September 1914 when the Eastern Caprivi was occupied by Southern Rhodesia. During the existence of the mandate the Union of South Africa had no competence either to enter into any express agreement to delimit the international boundary of South West Africa or to modify the prevailing subsequent practice with regard to the interpretation of Article III of the 1890 Anglo-German Agreement. Consequently, in my opinion, the subsequent practice of the parties for the purpose of interpreting the Anglo-German Agreement should be determined on the basis of the situation existing up to September 1914.
[pp. D.O. Parra-Anguren] 87. The evidence presented by Namibia demonstrates that Germany administered the Eastern Caprivi Zipfel through the Masubia Chiefs and their tribal organization. They exercised judicial functions and had authority to render judgments. Their positive acts of exercise of jurisdiction over Kasikili Island were frequent enough, taking into account that they were undertaken in areas sparsely populated and very remote from the centres of civilization, as the territory of South West Africa was described in Article 22, paragraph 6, of the League of Nations Covenant (see para. 27 above). The Bechuanaland authorities never challenged such jurisdictional acts. For this reason, in my opinion, the Chiefs were agents of the colonial administration and their acts represent the subsequent practice of the Parties for purposes of the interpretation of the 1890 Anglo-German Agreement.
[pp. D.O. Parra-Anguren] 88. The considerations set out in the foregoing sections lead to the conclusion that the Masubia of the Eastern Caprivi were the only tribesmen who occupied Kasikili/Sedudu Island, at least until 1914; that their occupation of Kasikili/Sedudu Island was peaceful and public; and that even Botswana acknowledged that their chiefs "became in a certain sense agents of the colonial administration" (see para. 85 above). Therefore, in my opinion, the subsequent practice of Germany and Great Britain reflected their understanding that Kasikili/Sedudu Island formed part of German South West Africa and that the southern channel of the Chobe River was the "main channel" referred to in Article III, paragraph 2, of the 1890 Anglo-German Agreement. No subsequent practice of the parties to the Treaty was possible during the First World War when British troops exercised de facto control over South West Africa. In 1920 the League of Nations confirmed the establishment of the Mandate over South West Africa. During the existence of the Mandate over South West Africa (Namibia) neither of the Parties to the 1890 Anglo-German Agreement had competence to recognize, either by express agreement or by subsequent practice, that the aforementioned "main channel" of the Chobe River was the northern channel and not the southern channel, since this new interpretation would have represented a modification of the territory submitted to the Mandate. Consequently, the original understanding was maintained and for this reason, in my opinion, Kasikili/Sedudu Island forms part of Namibia and the southern channel of the Chobe River is the "main channel" referred to in Article III, paragraph 2, of the 1890 Anglo-German Agreement.
