International law (IL) draws its legitimacy and authority from public affirmations and diffuse support for the rule of law, yet contestation about IL is to be expected. States collectively rule and contest international politics through the crafting, invocation, and interpretation of IL. The chapter explores both ordinary and extraordinary contestations of IL authority. Ordinary contestation takes place within a legal field, when lawyers, stakeholders, judges, and government officials debate, contest, and disagree about the meaning of IL. Political tactics are also part of ordinary contestation, but because the curators of IL authority are transnational, a state may be unable to impose its preferred IL interpretation. Instead, states can use three extra-ordinary contestation strategies to escape IL authority: they can 1) seek to replace international law’s authority with domestic law’s authority; 2) pit different international laws against each other by maneuvering within and around international regime complexes; and (3) attack the legitimacy and authority of international law altogether. Extraordinary contestation can make IL more accountable, but it can also undermine the permissive conditions that make IL both constraining and effective.