This article analyses the legal impact of colonial treaties on Africa with particular reference to the Anglo-German Treaty of 1913 by which the British ceded Bakassi to Germany. In 2002, the World Court delivered judgment in the Cameroon v. Nigeria case ceding the disputed Bakassi Peninsula to Cameroon. The Court relied heavily on the Anglo- German Agreement of 11 March 1913 to reach its decision. Since that judgment was delivered there has been controversy generated by Nigerian legal luminaries, scholars and public commentators. The legality of the Agreement entered into between Great Britain and Germany during colonial rule has been put to question. The judgment, though being implemented, is still under severe intellectual attack. The chief aims of this article are to find out the legal impact of the Agreement and the reasons the Court relied on it so heavily to reach its decision. This study is a legal history. It adopts a descriptive analysis method to interrogate relevant sources of information about the treaty. The article reveals that the Court relied on the Agreement based on a number of reasons. These included Britain’s right to cede Bakassi to Germany in 1913; lack of protest by Nigeria against the Anglo-German treaty during or after colonial rule; Nigeria’s acquiescence in the Agreement. The Nigerian legal team over- relied on effectivities or historical consolidation, but the Court held that Cameroon had a valid conventional title, which prevails over any effectivities or historical consolidation.