Territorial Sovereignty: A Philosophical Exploration offers a qualified defense of a territorial states-system. It argues that three core values-occupancy, basic justice, and collective self-determination-are served by an international system made up of self-governing, spatially defined political units. The defense is qualified because the book does not actually justify all the sovereignty rights states currently claim, and that are recognized in international law. Instead, the book proposes important changes to states' sovereign prerogatives, particularly with respect to internal autonomy for political minorities, immigration, and natural resources. Part I of the book argues for a right of occupancy, holding that a legitimate function of the international system is to specify and protect people's preinstitutional claims to specific geographical places. Part II turns to the question of how a state might acquire legitimate jurisdiction over a population of occupants. It argues that the state will have a right to rule a population and its territory if it satisfies conditions of basic justice and also facilitates its people's collective self-determination. Finally, Parts III and IV of this book argue that the exclusionary sovereignty rights to control over borders and natural resources that can plausibly be justified on the basis of the three core values are more limited than has traditionally been thought.