Abstract The colonial and postcolonial realities of international law have been obscured by the analytical frameworks that governed traditional scholarship on the subject. This article sketches out a history of the evolution of international law that focuses in particular on the manner in which imperialism shaped the discipline. It argues that colonialism, rather than being a peripheral concern of the discipline, is central to the formation of international law and, in particular, its founding concept, sovereignty. It argues that international law has always been animated by the civilising mission, the project of governing and transforming non-European peoples, and that the current war on terror is an extension of this project.