Enforcement and the concept of law

International law, many think, is not really law at all because it is not enforced. This Essay asks two philosophical questions about that claim. What do we mean by enforcement when we channel the intuition that enforcement is part of law's nature? And what is the place of enforcement in our concept of law? Enforcement, the Essay argues, is the activity by which a legally constituted power is applied to make the law's dictates actual; it is a matter of law's efficacy. Enforcement so conceived is constitutive of law's identity as law, but not strictly necessary to it because law is not the kind of thing that has strictly necessary features. Nor is enforcement sufficient to make a norm a law: the skepticism toward international law is not based on enforcement alone.