Domestic court decisions often make headlines around the world. For example, recent United States Supreme Court decisions about the International Court of Justice and the rights of foreign detainees held by the United States at Guantanamo Bay have attracted international attention. However, the role of domestic courts in the world extends far beyond headlines. Seemingly routine decisions on issues such as personal jurisdiction, forum non conveniens, choice of law, extraterritoriality, and arbitration have implications for global governance. Legal scholarship divides these issues into doctrinal categories like civil procedure, conflict of laws, and international law. But by doing so, it misses the bigger picture: for better or worse, domestic courts are pervasively involved in regulating transnational activity.This Article cuts across doctrinal categories to provide a systematic analysis of the global impact of domestic courts. It argues that domestic courts perform two global governance functions: they allocate governance authority, and they determine rights and obligations of transnational actors. It shows that these functions matter not only for litigants, but also for global welfare. And it proposes a method to critically evaluate these functions that moves beyond traditional litigant-focused assessments to analysis of the cross-border effects of domestic court decisions. This method will allow scholars and policy makers to develop the empirical foundations needed for the intensifying debate over the proper role of domestic courts in addressing global challenges.