Understanding Immigration Law

The fourth 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.

The new edition reviews the basics of immigration law and offers an expanded analysis of crimmigration law, the law surrounding the removal of criminal noncitizens, and immigration federalism, which addresses the ongoing tension between state and federal governments on immigration regulation. The closure of the border under the public health law known as Title 42 is discussed as an example of the incredible powers held by the President in immigration matters. President Trump has targeted sanctuary jurisdictions for immigration enforcement and deployed troops to assist in enforcement of the immigration laws in Los Angeles.

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

• President Trump's frontal assault on birthright citizenship and the litigation that has followed, including the Supreme Court's 2025 decision in Trump v. Casa, Inc.;
• Efforts to remove noncitizens without Due Process by declaring an "invasion" of the United States by migrants and invoking the Alien Enemies Act of 1798 and the Supreme Court's responses;
• The various increased enforcement measures, including warrantless raids, immigration operations at churches, schools, and courthouses, anti-terrorism measures and stricter inadmissiblity grounds, expanded use of detention (and the "end of catch-and-release" in the first and second Trump administrations ), public and workplace raids, removal of criminal noncitizens, including use of detention under the Laken Riley Act of 2025, and vast expansion of expedited removal; Latina/os have frequently claimed that they have been profiled in the operations;
• 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 and another ban that targeted Muslims and Africans by President Trump in his second term;
• The end of Temporary Protected Status and humanitarian parole for Salvadorans, Hondurans, Nicaraguans, Afghans, Venezuelans, Haitians, and nationals of several other countries;
• The failed attempt to rescind the Deferred Action for Childhood Arrivals (DACA) policy adopted by the Obama administration and updates on how litigation has in effect ended DACA;
• The efforts to punish state and local "sanctuary" jurisdictions that limit state and local cooperation with federal immigration enforcement efforts; and
• An expanded section on enforcement of the U.S./Mexico border, including discussion of the Migrant Protection Protocols in place in both Trump administrations.

Besides providing valuable historical context, the chapters comprehensively update the various chapters with Supreme Court immigration decisions, including the ones limiting the review of State Department consular visa decisions (Department of State v. Munoz (2024)), guaranteeing the due process rights of noncitizens before removal (A.A.R.P. v. Trump (2025) and Trump v. J.G.G. (2025)), requiring the U.S. government to facilitate the return of a noncitizen wrongfully deported to El Salvador, and the birthright citizenship case (Trump v. CASA, Inc. (2025)) in which the Court limited nationwide injunctions without addressing President Trump's effort to end birthright citizenship through executive order.