This book considers the case for modernizing partnership rights in EC family reunification law. Existing Community law guarantees immigration rights only to spouses and yet there is a growing diversity of national laws on registered partnerships and recognition of cohabitation. The Community institutions currently framing legislation seem to view this as a question that can be settled by political agreement with little or no outside constraint. The book challenges this assumption. Drawing on basic ECHR principles, the place of the ECHR in Community law, and on basic Community law principles of free movement and discrimination, the book argues that the right of a migrant EU Citizen to family reunification for a cohabiting partner is presumptively protected and therefore justification for refusing to admit such partners must be provided. It also considers the possible justifications for marriage-only immigration policies and concludes that although possible, such justifications are far from certain to succeed in the ECJ. The discussion on immigration rights also tackles the important question of whether judicial activism is appropriate or whether there should be judicial deference to the legislative process currently underway. The book concludes with a wider discussion of the proper response of Community law to the increasing diversity of Member States family laws and policies. The book will be of value not only to immigration lawyers, but also to those interested in partnership rights generally, as well as to a wider audience of EU lawyers, primarily academics but also graduate students and practitioners.