The legitimacy of universal jurisdiction over crimes against humanity, genocide, and war crimes has generated great attention among policy makers and scholars. This article argues that allowing for the participation of, and being accountable to, the international community, are two requirements of legitimacy that universal jurisdiction domestic statutes and proceedings should strive to meet. These are requirements for the legitimacy of universal jurisdiction regardless which conception of international law and international institutions one adopts — statist, cosmopolitan democracy, natural law, global administrative law or global constitutionalism. This article then analyses the important implications of these principles of international participation and accountability for a number of central debates on universal jurisdiction, namely, the crimes universal jurisdiction statutes and proceedings may include, the definition of these crimes, and which doctrines from the general part of international criminal law should be incorporated. These principles also affect how universal jurisdiction cases should be selected, what the relationship between universal jurisdiction prosecutions and the International Criminal Court should be, and which transparency and participatory requirements proceedings under universal jurisdiction should meet. In so doing, the author takes the German Code of Crimes against International Law as a case study to illustrate the analysis.