The chapter first examines how, as a technical matter, states give effect in their respective bodies of municipal criminal law and criminal procedure to the substantive law of international crimes and to the jurisdiction over such crimes permitted or mandated by international law, and what international law may say about aspects of this. It then considers technical, principled, and pragmatic questions relating to, specifically, the prosecution of international crimes at the national level, focusing on controversy over the exercise of universal jurisdiction. It lastly surveys the types of criminal courts to which states entrust the municipal adjudication of international crimes, highlighting in the process a variety of special municipal criminal courts established by specific states.