Substate nationalism, especially in the past fifteen years, has noticeably affected the political and territorial stability of many countries, both democratic and democratizing. Norms exist to limit the behavior of collective agents in relation to individuals; the set of universally accepted human rights provides a basic framework. There is a lacuna in international law, however, in the regulation of the behavior of groups toward other groups, with the exception of relations among states. The book offers a normative approach to moderate minority nationalism that treats minorities and majorities in multinational states justly and argues for the differentiation of group rights based on how group agents are constituted. It argues that group agency requires a shared set of beliefs concerning membership and the social ontology it offers ensures that group rights can be aligned with individual rights. It formulates a set of principles that, if adopted, would aid conflict resolution in multinational states. The book pays special attention to national self-determination in transitional societies. The book is intended for everyone in political philosophy and political science interested in global justice and international law and legal practitioners interested in normative issues and group rights