Over the last century, scholars of international relations and international law gradually parted company. This book argues that this mutual neglect is no longer tenable in a world where law and politics increasingly converge. For Arend, legal rules do in fact matter in world politics -- even if they are not established or enforced in the same way as domestic law. International legal norms are important because states consent to and respect legal rules. For its part, Arend argues, international law is rooted in politics; legal scholars who forget this basic insight risk becoming irrelevant in the global arena. Not surprisingly, the author looks to the European Union to show how law transformed relations between states as the legal character of European institutions underpinned political integration. Arend sees fundamental change under way, leading to a "neomedieval" system of multiple and overlapping legal authorities in which individuals simultaneously owe loyalties to ethnic communities, regional organizations, and transnational groups. But his speculations about the future are a bit murky.