The international regime on whale hunting is in crisis, despite its apparent success in rescuing most whale populations from extinction. Through the politics of legalization in world affairs, disagreement over the substance of whale hunting has been displaced, recast as disputes over legal technicalities of treaty interpretation and what counts as “scientific” research. The whaling regime has thus become a microcosm of the problems of international law and diplomacy, where a shared commitment to the rule of law coexists with deep disagreements over the meaning of compliance. The case illustrates what can go right and what can go wrong in the design of international institutions, and in the dynamics among state interests, regimes, and activists.