The rich field of inter-state water law in the United States illustrates both successes and failures in transboundary water management and allocation. In Inter-state Water Law in the United States of America: What Lessons for International Water Law?, this domestic field of transboundary water law is compared and contrasted with international transboundary water law. This analysis is accompanied by a discussion and evaluation of the different cases of shared watercourses that applied these approaches, and a comparison of each of them to similar approaches in international water law. The analysis draws lessons for international water law from inter-states water law - highlighting the successful inter-states approaches that can be adopted by international water law, as well as the approaches that failed, and which should be avoided.