Immigration law both screens migrants and regulates the behavior of migrants after they have arrived. Both activities are information intensive because the migrant’s “type” and the migrant’s post-arrival activity are often forms of private information that are not immediately accessible to government agents. To overcome this information problem, the national government can delegate the screening and regulating functions. American immigration law, for example, delegates extensive authority to both private entities— paradigmatically, employers and families—and to the fifty states. From the government’s perspective, delegation carries with it benefits and costs. On the benefit side, agents frequently have easy access to information about the types and activities of migrants and can cheaply monitor and control them. On the cost side, agents’ preferences are not always aligned with those of the national government. The national government can ameliorate these costs by giving agents incentives to act consistently with the government’s interests. Understanding these virtues and vices of delegation sheds light on longstanding debates about the roles that employers, families, and states play in American immigration law.