This chapter explores the exercise of state power and state authority over human mobility. Scholars note that local police officers in South Africa have enormous discretion to implement immigration laws and to decide which forms of human mobility will be permitted to take place. World War I definitively ended the liberal migration regime of the late 19th century. The social dynamics of migration, moreover, are such that population flows have a self-sustaining quality to them. The US Immigration Control and Reform Act of 1986 (IRCA) often serves as the paradigmatic example of the influence of special interest groups on immigration policy. The incapacity of states to control migration flows is at times attributed partly to the dynamics of globalization. Joseph Carens argues that 'citizenship in Western liberal democracies is the modern equivalent of feudal privilege an inherited status that greatly enhances one's life chances'.