Sex offender residency restrictions have proliferated throughout the United States over the past decade. A number of commentators have likened these laws to medieval banishment, when political outcasts and undesirables are exiled to remote areas where they cannot threaten civilized society. This Article argues first that likening modern residency restrictions to “banishment” largely misconstrues this practice as it has been practiced historically. Instead, these statutory initiatives are better understood as an assertion of governments’ police power to protect public health, safety, and morality. Seen through this lens, this Article evaluates the laws’ constitutional sufficiency with attention to their allegedly punitive nature and the effect, if any, of the modern use of quarantine to justify deprivations of liberty in the interest of public safety. It also discusses the relevance of substantive due process in this context, with particular focus on the Supreme Court of California’s groundbreaking March 2015 decision invalidating its sex offender residency statute on this basis. Recognizing the uncertainty inherent in constitutional challenges to sex offender residency laws, this Article concludes with recommendations on how best to implement sensible public policy reform in the present landscape.