This is a seminar about migration control. It begins with a review of the legal basis for what is assumed to be the sovereign right of every state to exclude non-citizens from its territory. This absolutist legal claim, exemplified by the assertion that the U.S. Congress has “plenary power” to exclude or deport all aliens, is critically examined in the light of the work of leading theorists on the role of borders in defining the functions and values of the liberal state. The seminar next considers recent social science literature on the nature of contemporary movements of persons between states, leading to a critique of the adequacy of immigration laws as traditionally conceived to meet the challenge of modern transnational migration.