(Botswana / Namibia)
Judgment of 13 December 1999
On 29 May 1996, Botswana and Namibia jointly notified to the Registrar the text of a Special Agreement signed at Gaborone (Botswana) on 15 February 1996 and having entered into force on 15 May 1996 for the submission to the Court of a dispute between them concerning the boundary around Kasikili/Sedudu Island. The Special Agreement referred inter alia to a Treaty signed on 1 July 1890 between Great Britain and Germany delimiting their respective spheres of influence in Africa. Under the terms of the Special Agreement, the Parties asked the Court 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". The island in question, which in Namibia is known as Kasikili, and in Botswana as Sedudu, is approximately 3.5 square kilometres in area, is located in the Chobe River, which divides around it to the north and south, and is subject to flooding of several months' duration, beginning around March each year.
The Court based its reasoning on the text of the 1890 Treaty which, in respect of the region concerned, locates the dividing line between the spheres of influence of Great Britain and Germany in the "main channel" of the River Chobe. In the Court's opinion, the real dispute between the Parties concerned the location of that main channel, Botswana contending that it is the channel running north of Kasikili/Sedudu Island and Namibia the channel running south of the island. Since the Treaty does not define the notion of "main channel", the Court itself proceeded to determine which is the main channel of the Chobe River around the Island.
In order to do so, it took into consideration, inter alia, the depth and the width of the channel, the flow (i.e., the volume of water carried), the bed profile configuration and the navigability of the channel. After having considered the figures submitted by the Parties, as well as surveys carried out on the ground at different periods, the Court concluded that the northern channel of the River Chobe around Kasikili/Sedudu Island had to be regarded as its main channel.
After evoking the object and purpose of the 1890 Treaty, and its travaux préparatoires, the Court examined at length the subsequent practice of the parties to the Treaty. The Court found that this practice did not result in any agreement between them regarding the interpretation of the Treaty or the application of its provisions. The Court further stated that it could not draw conclusions from the cartographic material in view of the absence of any map officially reflecting the intentions of the parties to the 1890 Treaty and in the light of the uncertainty and inconsistency of the maps submitted by the Parties to the dispute.
The Court finally considered Namibia's alternative argument that it and its predecessors had prescriptive title to Kasikili/Sedudu Island by virtue of the exercise of sovereign jurisdiction over it since the beginning of the century, with full knowledge and acceptance by the authorities of Botswana and its predecessors. The Court found that while the Masubia of the Caprivi Strip (territory belonging to Namibia) did indeed use the Island for many years, they did so intermittently, according to the seasons, and for exclusively agricultural purposes, without it being established that they occupied the Island à titre de souverain, i.e., that they were exercising functions of State authority there on behalf of the Caprivi authorities. The Court therefore rejected this argument.
After concluding that the boundary between Botswana and Namibia around Kasikili/Sedudu Island followed the line of deepest soundings in the northern channel of the Chobe and that the Island formed part of the territory of Botswana, the Court recalled that, under the terms of an agreement concluded in May 1992 (the "Kasane Communiqué"), the Parties have undertaken to one another that there shall be unimpeded navigation for craft of their nationals and flags in the channels around the Island.
In her Declaration on the judgment, Judge Higgins emphasized the need to take into account contemporary knowledge in the area, which would point to a lesser role of the navigability of the river and a greater weight on the physical appearance of the area. Judge Ranjeva, in his Declaration, interpreted the findings of the Court as the least improbable solution in the absence of a systematic comparison of the two channels of the river. Judge Koroma stressed that the equal use of the river for navigation, as set out in the Kasane Communiqué, reflected contemporary principles of the law of international watercourses.
Judge Oda, in a Separate Opinion, deplored the fact that the Court had not sought the assistance of experts in order to clarify the location of the main channel. Moreover, unlike the Court, he considered as important the practice of several decades to regard the northern channel as separating the banks of the Chobe River. Judge Kooijmans found that Namibia's argument based on prescription should have been declared inadmissible given the relevance of the 1890 treaty; he also stressed that the rule of equitable utilization of watercourses, as contained in the Kasane Communiqué, had become well-established in international law.
Vice-President Weeramantry and Judges Parra-Aranguren and Rezek, in their Dissenting Opinions, placed special emphasis on the unopposed use of the island in question by the Masubian people. Judges Parra-Anguren and Rezek also regretted that the Court had accorded too little weight to other instances of subsequent practice, to the equitable use of watercourses and cartography. Judge Fleischhauer, in his Dissenting Opinion, likewise disagreed with the Court's finding of the northern channel as the boundary. In the view of Vice-President Weeramantry, who, like the other dissenters, regarded the Island as belonging to Namibia, a joint international régime should have been set up to safeguard environmental interests.