Law, after all, constrains power, and the United States, like any great power, is likely to support a law-bound international order only if it ties up the power of its competitors more than it constrains its own. Other great powers have subscribed to this realist calculus in advancing international law. America is exceptional in combining standard great-power realism with extravagant idealism about the country’s redemptive role in creating international order. Since Franklin Roosevelt’s leadership in setting up the United Nations and the Nuremberg trials, the US has promoted universal legal norms and the institutions to enforce them, while seeking by hook or by crook to exempt American citizens, especially soldiers, from their actual application. From Nuremberg onward, no country has invested more in the development of international jurisdiction for atrocity crimes and no country has worked harder to make sure that the law it seeks for others does not apply to itself.