This book investigates the continuity and change of sovereignty as a key concept to the disciplines of International Relations (IR) and International Public Law, and international politics as a practice.Theoretically scrutinising 'sovereignty' across disciplinary boundaries, it argues that in order to solve the sovereignty puzzle, sovereign statehood needs to be assessed as a human arrangement, an institutional product of modern international society, pertaining to both politics and law. Inspired by constructivist insights, Aalberts explores and addresses sovereignty: as an institution, as identity; as a game; and as a form of discipline and subjectivity.Linking theoretical insights to contemporary discussions about 'pooling sovereignty' in the context of European integration, 'failed states' in Sub-Saharan Africa, and the reinterpretation of sovereignty as a 'responsibility to protect' in the context of the United Nations, and the disciplinary working of sovereignty as exemplified in the Counterterrorist Committee, this book will be of interest to students and scholars of international relations, international relations theory and law.