This article argues that the fields of international law and organization are experiencing a legitimacy crisis relating to fundamental reconfigurations of global power and authority. Traditional Westphalian-inspired assumptions about power and authority are incapable of providing contemporary understanding, producing a growing disjunction between the theory and the practice of the global system. The actors, structures, and processes identified and theorized as determinative by the dominant approaches to the study of international law and organization have ceased to be of singular importance. Westphalian-inspired notions of state-centricity, positivist international law, and ‘public’ definitions of authority are incapable of capturing the significance of non-state actors, informal normative structures, and private, economic power in the global political economy.