This volume presents the latest research by some of the world's leading figures in the fast growing area of immigration studies. Relating the study of immigration to wider processes of social change, the book focuses on two key areas in which nation-states are being challenged by this phenomenon: sovereignty and citizenship. Bringing together the separate clusters of scholarship which have evolved around both of these areas, Challenge to the Nation-State disentangles the many contrasting views on the impact of immigration on the authority and integrity of the state. Some scholars have stressed the stubborn resistance of states to relinquish territorial control, the continued relevance of national citizenship traditions, and the 'balkanizing' risks of ethnically divided societies. Others have argued that migrations are fostering a post-national world. In their view, states' immigration policies are increasingly constrained by global markets and an international human rights regime, membership as citizenship is devalued by new forms of postnational membership for migrants, and national monocultures are giving way to multicultural diversity. Focusing on the issue of sovereignty in the first section, and citizenship in the second, this compelling new study seeks to clarify the central stakes and opposing positions in this important and complex debate.