Despite a wealth of literature exploring the issues surrounding it, the legitimacy and authority of international criminal law remain in question. Adopting a perspective informed by legal and political philosophy, Clare Frances Moran considers the authority of international criminal law, why it can be conceived of as more than simply an exercise of power and how that power may be exercised legitimately. Advancing existing scholarship on the subject, Moran explores the roots of the authority of law at the domestic level and tests these ideas in an international context. She examines sovereignty, complementarity and postcolonial issues, and how each impact international criminal law. By developing a theory on the authority of international law, Moran considers how it might be possible to adjudicate more effectively at the international level.