This paper argues that cosmopolitan law has been more successfully achieved not by appeal to a supra-state authority or community, but by the development of features of existing treaty law. Specifically, it shows how the International Criminal Court's jurisdiction over serious human rights violations has been extended to the citizens and territories of non-member states – and even to otherwise immune state officials – not by challenging the sovereignty of non-member states directly, but on the basis of member states’ own territorial sovereignty and the universal jurisdiction which they delegate to the Court and to the United Nations Security Council. In light of this, the authors argue that cosmopolitanism is better conceived not as invoking an independent sense of global community that supersedes and constrains state sovereignty, but as an immanent, contingent and creative development of statist criminal law itself, rooted in its principles of state sovereignty.