This Article examines the development of the International Criminal Court, outlines the positions of and disagreements between Britain and the United States concerning the ICC, and analyzes the specific objections to the ICC raised by the United States. In this discussion, the Article argues that the contrasting positions of Britain and the United States toward the ICC can be understood in terms of each nation’s differently configured perception of its own sovereign power. For various reasons, Britain’s sovereignty is tested most acutely by its relationship with the European Union, while the United States feels its sovereignty encroached primarily by its relationship with the United Nations. Britain and the United States share a commitment to constitutionalism and this commitment has grounded Anglo-American support for international war crimes tribunals in the past. In the end, the ICC raises the question whether constitutionalism is a domestic or a universal conception.