Developments in international politics since the end of the Cold War point to a new international order in the twenty-first century. At its heart is international law. Global community values have been recognised as providing the basis for formal legal obligations, maintained and implemented by an international constitutional order. Ironically, however, this order is fundamentally challenged by the increasingly unilateralist attitude of the United States in world affairs, and its disregard for the underpinnings of the order that it was instrumental in creating. Marc Weller considers the future of international law in the context of the competition between the development of an international constitutional order on the one hand, and the tendency toward unipolarity on the other. If it continues, this tendency threatens to fatally undermine the international constitutional order that has been established thus far. This book offers new insights into the structure and workings of the international system for students and practitioners of international relations and international law. Its lively and accessible style will also appeal to the interested general reader.