What is the criminal law for? At its most elemental, criminal law secures the possibility of a shared life under stable and just public institutions. In the age of the administrative state, criminal law performs this task by stabilizing cooperation across a wide range of contexts, from backstopping compliance with tax law to protecting the integrity of a nation’s fisheries. How should we decide when this is a legitimate use of the criminal law? The “public law” conception sketched in this book suggests that because the criminal law is a public institution, it should be evaluated by the very same values that we structure our evaluation of public institutions generally. In contrast to familiar forms of retributivism, the public law conception starts from the political morality of public institutions, rather than the interpersonal morality of private relationships. In a society with democratic and egalitarian aspirations, the legitimacy of the criminal law depends in part upon the democratic and egalitarian character of the institutions it supports, and in part upon its supporting those institutions by means that are themselves consistent with democratic and egalitarian principles. The particular account of those principles sketched in this book is democratic, egalitarian without being equalizing, and focused on a form of freedom—effective access to central capability—as its currency of evaluation. This approach provides a distinctive and illuminating framework for assessing a wide range of problems in criminal law and policy, from mass incarceration, to over-criminalization and the allocation of procedural rights.