This book presents seminal new work on the ethics of movement and membership. All the chapters contained in this volume address challenging and under-researched themes on the subject of migration. The chapters debate the question of the scope of the right to freedom of movement, whether we ought to recognize a human right to immigrate, and whether it might be legitimate to restrict emigration. They critically examine criteria for selecting between would-be immigrants, and for acquiring citizenship, as well as the tensions between the claims of prospective immigrants and existing residents. They tackle questions of migrant worker exploitation, and responsibility for refugees. All the chapters illustrate the importance of drawing on the tools of political theory to clarify, criticize, and challenge the current terms of the migration debate.