This book addresses the constitutional issues, both in theory and in practice, that accompany the existence of national diversity in pluralist democracies. Tierney contends that the democratic plurinational state, characterized by the presence of more than one national group within the State, is a discrete category of multi-level polity which defies the standard classifications of liberal constitutionalism. Building upon this theoretical basis, the book focuses upon recent developments toward the institutional accommodation of Catalonia, Quebec, and Scotland. Tierney examines the legal issues which arise from the challenges posed by sub-state nations within multinational democracies to the constitutional and institutional structures of particular States, and also to some of the fundamental precepts of democratic constitutional theory and practice.