Dual nationality has become one of the most divisive issues linked with the politics of migration in Germany and the US. This volume, the first one in decades to focus on this issue, examines the history, consequences and arguments for and against dual citizenship, and uses dual nationality as the basis of a reflection on important issues closely related to it: social rights, European citizenship and federal citizenship. It pays particular attention to questions such as: What are the major arguments in favour and against dual nationality? Why has dual nationality provoked such contrasting responses, being a non-issue in the UK, for instance, and an extremely controversial one in Germany? How is dual nationality used by states to influence politics and policy in other states? How does it relate to the aim of integrating ethnic migrants and to broader issues in social policy and European integration?