Breaking and making norms: American revisionism and crises of legitimacy

International norms are influential when they are seen as legitimate, and recent American behaviour may undermine the legitimacy of norms on the use of force. I examine three kinds of legitimacy crisis that might arise from American revisionism. First, the US threatens to delegitimate the norms that it challenges, particularly on military preemption. Second, it threatens to undermine its own influence by disassociating American power from one source of legitimation. Finally, it may negate the basic idea of American hegemony as that term is understood in constructivist scholarship and so transform the structure of the international system. Any of these might lead to a crisis, though of different kinds. The American challenge to the customary law on preemption threatens to delegitimize both the existing norms and the social basis of US power, while also attempting to legitimize American interests and new understandings of the norms. It therefore shows the productive and destructive aspects of the power of legitimation in world politics. Legitimation is the link between states and the normative structures of international society.