His work as a political sociologist focuses on understanding migration, race, ethnicity, law, and citizenship in an international field of politics. Cook-Martin is also author of The Scramble for Citizenship: Dual Nationality and State Competition for Immigrants. David FitzGerald is Associate Professor of Sociology at UC San Diego and co-Director of the Center for Comparative Immigration Studies. His research aims to understand laws and policies regulating international migration as a total system of interactions among actors in countries of origin and destination. FitzGerald is also author of Nation of Emigrants: How Mexico Manages its Migration.