The substance-procedure dichotomy is a popular target of scholarly criticism because procedural law is inherently substantive. This article argues that substantive law is also inherently procedural. I suggest that the construction of substantive law entails assumptions about the procedures that will apply when that substantive law is ultimately enforced. Those procedures are embedded in the substantive law and, if not applied, will lead to over- or under-enforcement of the substantive mandate. Yet the substance-procedure dichotomy encourages us to treat procedural systems as essentially fungible—leading to a problem of mismatches between substantive law and unanticipated procedures. I locate this argument about the procedural foundation of substantive law within a broader discussion of the origin and status of the substance-procedure dichotomy.