What Is Immigration Law? Visas, Green Cards, Asylum, and Deportation Explained

The Framework of U.S. Immigration Law

Immigration law in the United States is almost exclusively federal — the power to regulate immigration is vested in Congress under Article I, Section 8 of the Constitution, and states have very limited authority to enact their own immigration rules. The primary statute is the Immigration and Nationality Act (INA), first enacted in 1952 and amended many times since, most significantly by the Immigration Reform and Control Act of 1986 and the Illegal Immigration Reform and Immigrant Responsibility Act of 1996.

The federal agencies responsible for immigration include U.S. Citizenship and Immigration Services (USCIS), which adjudicates immigration benefits; U.S. Immigration and Customs Enforcement (ICE), which handles interior enforcement and removal; and U.S. Customs and Border Protection (CBP), which enforces immigration law at ports of entry and along the border. The Executive Office for Immigration Review (EOIR) within the Department of Justice operates the immigration court system.

Visa Categories

Visas are documents that permit a foreign national to seek entry to the United States for a defined purpose. They fall into two broad categories: immigrant visas, which lead to permanent residency (a green card), and nonimmigrant visas, which allow temporary stays for specific purposes.

Major nonimmigrant visa categories include: B-1/B-2 (business and tourism); F-1 (academic student); J-1 (exchange visitor, including scholars, researchers, and au pairs); H-1B (specialty occupation workers, capped at 85,000 per year); L-1 (intracompany transferees); O-1 (individuals with extraordinary ability); TN (professionals from Canada and Mexico under the USMCA); and many others. Nonimmigrant visas are typically issued for a defined period and require the holder to maintain their nonimmigrant intent — though some statuses allow dual intent (the ability to seek permanent residency while on a temporary visa).

The Green Card Process

A green card (officially a Permanent Resident Card, Form I-551) grants the holder the right to live and work permanently in the United States. There are four main pathways to a green card.

Family-based immigration accounts for the largest share of green cards. Immediate relatives of U.S. citizens (spouses, unmarried children under 21, and parents) receive priority and are not subject to annual caps. Other family relationships — adult children, married children, and siblings of U.S. citizens, and spouses and children of permanent residents — are subject to annual numerical limits and can face wait times of many years, sometimes decades, depending on the applicant's country of birth.

Employment-based immigration is divided into preference categories based on skills and qualifications, from priority workers (EB-1) and professionals with advanced degrees (EB-2) to skilled workers and professionals (EB-3) and investors (EB-5). Annual caps and per-country limits create significant backlogs for workers from high-demand countries such as India and China, who may wait decades for a green card even with an approved petition.

Diversity Visa Lottery (the DV Lottery) makes approximately 50,000 visas available annually to nationals of countries with historically low rates of immigration to the United States. Applicants are selected by random computer draw, subject to standard admissibility requirements.

Humanitarian pathways include asylum and refugee status (discussed below), as well as special immigrant categories for victims of crime (U visa), trafficking (T visa), and domestic violence (VAWA self-petitions).

The Naturalization Process

Naturalization is the process by which a lawful permanent resident becomes a U.S. citizen. General requirements include: five years of continuous permanent residency (three years if married to a U.S. citizen); continuous physical presence in the United States for at least half of the statutory period; good moral character; ability to read, write, and speak English; knowledge of U.S. history and civics (demonstrated through a standardized test); and an oath of allegiance to the United States.

Children born abroad to U.S. citizen parents may acquire citizenship automatically at birth under certain conditions, and children who obtain a green card while under 18 in the legal and physical custody of a U.S. citizen parent automatically become citizens under the Child Citizenship Act of 2000, without a formal naturalization process.

Deportation and Removal Proceedings

Removal proceedings are the legal process by which the U.S. government seeks to compel a non-citizen to leave the country. Grounds for removal include unlawful entry, visa overstay, commission of certain crimes (including aggravated felonies and crimes of moral turpitude), fraud in obtaining immigration benefits, and national security concerns.

Removal proceedings are conducted before immigration judges in administrative courts. Non-citizens have the right to be represented by an attorney but — unlike criminal defendants — there is no right to government-appointed counsel in immigration proceedings, even when the respondent is detained. Those ordered removed may appeal to the Board of Immigration Appeals (BIA) and then to the federal circuit courts of appeals.

Certain forms of relief from removal may be available, including cancellation of removal (for long-time residents with qualifying family ties and hardship), voluntary departure, adjustment of status to a green card, and prosecutorial discretion by DHS to defer action on certain low-priority cases.

Asylum and Refugee Protection

Asylum is a form of protection available to individuals already in the United States or seeking entry at a port of entry who have suffered persecution or have a well-founded fear of persecution based on race, religion, nationality, membership in a particular social group, or political opinion. Asylum must generally be sought within one year of arrival in the United States (with limited exceptions). Individuals granted asylum may apply for a green card one year after approval.

Refugee status is similar in its legal standards but is sought from outside the United States through a separate overseas processing system. Refugees are admitted up to an annual ceiling set by the President after consultation with Congress.

DACA and Deferred Action

The Deferred Action for Childhood Arrivals (DACA) program, established by executive action in 2012, provides two-year renewable deferrals of removal and work authorization to individuals who were brought to the United States as children and meet educational and other requirements. DACA does not provide a path to a green card or citizenship, and its legal status has been challenged repeatedly in federal courts, creating significant uncertainty for its approximately 580,000 beneficiaries.