The third edition of Understanding Immigration Law lays out the basics of U.S. immigration law in an accessible way to newcomers to the field. It offers background about the intellectual, historical, and constitutional foundations of U.S. immigration law. The book also identifies the factors that have historically fueled migration to the United States, including the economic "pull" of jobs and family in the United States and the "push" of economic hardship, political instability, and other facts of life in the sending country.

Each chapter has been updated to analyze the unprecedented number of immigration enforcement measures—and many simply unprecedented measures—taken by the Trump administration, including but not limited to:

• The various increased enforcement measures, including expanded detention (and the "end of catch-and-release"), workplace raids, and restoration of Secure Communities (which the Obama administration had dismantled);
• The "zero tolerance" policy directed at Central American asylum seekers, including the policy to separate minors from parents in immigration detention centers;
• The "Muslim"" or "travel ban" upheld by the U.S. Supreme Court;
• The end of Temporary Protected Status for Salvadorans, Hondurans, Nicaraguans, Haitians, and nationals of several other countries;
• The attempt to rescind the Deferred Action for Childhood Arrivals (DACA) policy adopted by the Obama administration; and
• The efforts to discourage state and local "sanctuary" policies that limit state and local cooperation with federal immigration enforcement efforts.

The chapters further update the various chapters with Supreme Court immigration decisions, including the Court's decision invalidating a removal ground on due process grounds (Sessions v. Dimaya (2018)) and invalidating a derivative citizenship rule for violating Equal Protection (Sessions v. Morales-Santana (2017)).