This paper critically analyzes the concept of legitimacy as it applies to international criminal law. Using the referral of the situation in Darfur to the International Criminal Court (icc) – and the resultant disagreement between Sudan, the African Union, and the icc – as an entry point, it examines the discourse about the referral as a contest of legitimacy. After placing this specific example in the context of theories of legitimacy, it argues that there are no objective criteria for determining the legitimacy of an international criminal tribunal. Legitimacy as a concrete concept is best understood as a Kantian antinomy – an unanswerable question that borders on the metaphysical. Yet this indeterminacy can be turned to the advantage of the critical theorist, offering pragmatic, normative, and pluralist alternatives for the reconstitution of international criminal tribunals such as the icc.