This article considers whether the 2005 Comprehensive Peace Agreement for the Sudan (the CPA) gives rise to binding obligations for the parties under international law. The legitimacy and effectiveness of the CPA, and the avoidance of a return to bloody civil war, depends significantly on the Agreement giving rise to legal obligations. While it has been held in arbitration that the CPA is not a treaty, this article suggests that it is a binding international agreement and further that there are obligations concerning the outstanding referendum for the people of the Abyei region. The legal issues of the CPA are more complex than they at first appear and they engage deeper and broader questions of the role of international law. The article will suggest among other things that the Sudan situation demonstrates it is difficult to draw immutable general rules in abstraction about the international law relating to peace agreements and to self-determination.