The international law of sovereign immunity derives from state practice embodied in national judicial decisions and legislation. Although some U.S. Supreme Court decisions refer to this body of law using terms like “grace and comity,” the customary international law of sovereign immunity is law, which national courts should consider when arriving at immunity decisions. While it would be possible for a widely followed international treaty to work changes in customary international law, the UN Convention on Jurisdictional Immunities of States and Their Property has not done so yet. National legislation such as the U.S. Foreign Sovereign Immunities Act can precipitate changes in the international law of sovereign immunity, as can innovative lawsuits prompting national courts to reexamine theories of immunity. The International Court of Justice should refrain from interfering with the ability of national institutions to provide remedies for wrongful conduct of the type involved in Germany’s suit against Italy.