This paper examines the 1994 Declaration of Principles (DoP) for the resolution of the Sudanese civil war, adopted by the Inter-Governmental Authority on Development (IGAD). This was the only occasion on which an African inter-state organization included separation as an option for resolving a civil war. It was the basis for South Sudan’s independence in 2011. The DoP was drafted by the Ethiopian government, and imposed on belligerent parties, both of which were, at the time, unionist. The paper identifies two concepts of self-determination within the DoP— independence for colonial territories and the Marxist-Leninist idea of self-determination for national groups. The rationale for including both arose from Ethiopian leadership within IGAD. The paper also examines the diverse Sudanese debates on self-determination, including several strands of nationalism, Islamism, and the ‘New Sudan’ of the Sudan People’s Liberation Movement (SPLM). There was radical disagreement among Sudanese on national identity and self-determination, creating ambiguities that ironically facilitated the exercise in southern self-determination in 2011. Drawing on documentation of Sudanese negotiations, the paper examines how the DoP unlocked the Sudanese debate on the issue, and how the different concepts fared up to the time of the independence of South Sudan.