The European Union’s (EU) fundamental principles on free movement of persons and non-discrimination have long challenged the traditional closure of the welfare state.Although EU-wide free movement and national welfare appeared largely unproblematic before Eastern enlargement, the increased differences among EU member states in economic development and welfare provision have resulted in fears about potential welfare migration. Because rights of EU citizens were shaped to an important extent by jurisprudence of the European Court of Justice, these are often not very clearly delineated, and easily politicised. This comprehensive volume shows the normative limits of a strict non-discriminatory approach to EU citizens’ access to national welfare and analyses how the Court developed its jurisprudence, partly reacting to politicisation. Although, empirically, free movement negatively impacts national welfare only under extreme conditions, it is notable that member states have adjusted their social policies in reaction to EU jurisprudence and migration pressure alike. Their heterogeneous institutions of national welfare, administration and labour markets imply for member states that they face very different opportunities and challenges in view of intra-EU migration.This book was originally published as a special issue of the Journal of European Public Policy.