This chapter shows how the police power is justified and limited when it is structured consistent with natural rights. The power to regulate is the power to “make rights regular,” that is, to establish positive law rules that give citizens in practice freedom corresponding fairly to the freedom to which they’re entitled by natural law. Regulations can rely on any of three basic models. Some regulations make rights determinate. Some regulations prevent harm; they institute in public law prohibitions against violating rights, and they supply remedies for violations of the prohibitions. Some regulations secure average reciprocities of advantage. Those regulations reorder positive law rights when doing so seems likely in practice to serve rights-holders’ interests in using their possessions better than existing rights would. Laws that satisfy none of these three models may still be just laws – but they do not constitute just regulations and they need to be justified consistent with some other model of government action. This chapter responds to skeptical critiques of the police power influential in modern US Supreme Court case law and scholarship.