Guinea-Bissau–Senegal border

Between the Casamance and the Cacheu

Portuguese mariners explored this coast by the mid-15th century, and France extended its control inland from the Senegal coast during the 19th. A Franco-Portuguese convention of 12 May 1886 ran the boundary from Cap Roxo at an equal distance from the Casamance and Cacheu rivers, then along the parallel of 12°40′ N. Joint commissions marked it with pillars numbered 1 to 184 between 1900 and 1905, placing the “parallel” sector slightly north of the line itself.^[1]

“a line beginning at Cap Roxo and running, insofar as the landmarks permit, at an equal distance from the Cozamance and San Domingo de Cacheu Rivers”^[1]

The sea line

Negotiating from 1977, the two countries could not agree their maritime boundary and in 1985 put it to a three-member tribunal. The first question was whether a 1960 exchange of letters between France and Portugal still bound them. On 31 July 1989 the tribunal found that it did, and did not go on to draw a line itself.^[2]

Guinea-Bissau took Senegal to the International Court of Justice, arguing that the award did not exist, because its president had appended a declaration at odds with it, or was void, because it left the second question unanswered and gave no map. In its judgment of 12 November 1991 the court rejected these arguments and upheld the award.^[2]