This volume collects recent research by some of the world's leading figures in the fast-growing area of immigration studies. Relating the study of immigration to other, 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. Separate clusters of scholarship have evolved around both areas, and this work attempts to unite these camps, sorting out the many contrasting views on the influences of immigration upon the state's authority and integrity. Focusing on the issue of sovereignty in the first section, and then on citizenship in the second, this compelling new study seeks to clarify the central stakes and opposing positions in this debate.