The ABC’s of U.S. Immigration Law

The body of law governing immigration is called the Immigration and Nationality Act (INA). The Act classifies most people as U.S. citizens or “aliens” (noncitizens).

Who Is a U.S. Citizen?

  1. A person born in the United States, with narrow exceptions, is a citizen, according to the Fourteenth Amendment to the U.S. Constitution.
  2. By statute, a person born in certain U.S. territories is a citizen. This currently includes Guam, the Northern Mariana Islands, Puerto Rico, and the U.S. Virgin Islands.
  3. A lawful permanent resident (LPR), i.e., green card holder, may be eligible to apply for naturalization. In order to qualify, generally, an individual must have had LPR status for at least five years (or three years if they obtained the green card through a U.S.-citizen spouse). An applicant must be at least 18 years old, demonstrate “good moral character,” and pass English and U.S. history and civics exams (with certain exceptions). See our firm’s Guide to Naturalization in the United States.
  4. A child born abroad to one or two U.S. citizen parents may automatically acquire citizenship. See our firm’s Guide to Acquisition of U.S. Citizenship by Birth Abroad.
  5. A child born abroad and currently living in the U.S. as an LPR may automatically derive naturalization if they are living in the custody of at least one U.S. citizen parent. See Child Citizenship Act of 2000.
  6. A child born abroad and currently residing abroad may be eligible to apply for naturalization if they have at least one U.S. citizen parent who has been physically present in the U.S. for 5 years. See Child Citizenship Act of 2000.


Noncitizens can qualify as immigrants, nonimmigrants, or for other immigration benefits:


Immigrants, also known as lawful permanent residents (LPRs) or green card holders, are eligible to remain in the U.S. indefinitely. Eligibility is usually based on sponsorship by a family member (family-sponsored immigration) or possessing skills that are valuable to the U.S. economy (employment-based immigration). The INA allows admission of 675,000 immigrants each year, plus admission of U.S. citizens’ immediate relatives (spouses, parents, and children under age 21) without limit.


Nonimmigrants are persons holding temporary visas. Nonimmigrant visas are designated by letters (e.g., B-2 visitor for business, F-1 student, H-1B professional, L-1 intracompany transferee):

Other Immigration Benefits

Other immigration benefits include Temporary Protected Status, Asylees, refugees, DACA, etc.:

Employment Eligibility Verification

As part of the Immigration Reform and Control Act of 1986, the Form I-9 is used to verify the identity and confirm the employment authorization of individuals hired for employment in the United States. All U.S. employers must ensure proper completion of the Form I-9 for each individual they hire for employment in the United States. This includes citizens and noncitizens.