United States citizenship can be acquired by birthright in two situations: by virtue of the person's birth within United States territory or because one or both of their parents is (or was) a US citizen. Birthright citizenship contrasts with citizenship acquired in other ways, for example by naturalization.
Birthright citizenship is guaranteed to most people born on U.S. territory by the first part of the Citizenship Clause introduced by the Fourteenth Amendment to the United States Constitution (adopted July 9, 1868), which states:
"All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside."
The Amendment overrode the Supreme Court decision in Dred Scott v. Sandford (1857) that denied US citizenship to African Americans, whether born in the United States or not, and whether a slave or a free person. Pursuant to the Fourteenth Amendment and the Immigration and Nationality Act (INA) a person born within and subject to the jurisdiction of the United States automatically acquires US citizenship, known as jus soli ("right of the soil"). This includes the territories of Puerto Rico, the Marianas (Guam and the Northern Mariana Islands), and the U.S. Virgin Islands. The "subject to the jurisdiction thereof" clause excluded Native Americans living under tribal sovereignty, and U.S.-born children of foreign diplomats. Birthright citizenship was later extended to U.S.-born Native American subjects by the Indian Citizenship Act of 1924. Federal law also grants birthright citizenship to children born elsewhere in the world to U.S. citizens (with certain exceptions), known as jus sanguinis ("right of blood").
Some people oppose the application of birthright citizenship to children of illegal aliens. Some argue citizenship is not guaranteed by the Fourteenth Amendment to the children of illegal aliens, but this interpretation has never been endorsed by federal courts. The Pew Hispanic Center estimates that approximately 7.5% of all births in the U.S. (about 300,000 births per year) are to illegal aliens. The Pew Hispanic Center also estimates that there are 4.5 million children born to illegal aliens who received citizenship by birth in the United States, while the Migration Policy Institute estimates that there are 4.1 million children. Both estimates exclude anyone 18 and older who might have benefited.
On January 24, 2020, the Trump administration adopted a policy to make it more difficult for pregnant foreign women to come to the US where it is suspected that the purpose is to give birth on US soil and thereby to ensure their children become US citizens, a practice commonly called "birth tourism".
Current U.S. law
Citizenship in the United States is a matter of federal law, governed by the United States Constitution.
Since the adoption of the Fourteenth Amendment to the United States Constitution on July 9, 1868, the citizenship of persons born in the United States has been controlled by its Citizenship Clause, which states: "All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside."
Statute, by birth within U.S. Under United States Federal law (), a person is a United States national and citizen if: the person is born in the United States, and subject to the jurisdiction thereof the person is born in the United States to a member of an Indian, Inuit, Aleutian, or other aboriginal tribe (see Indian Citizenship Act of 1924) the person is of unknown parentage found in the United States while under the age of five years, until shown, prior to his attaining the age of 21 years, not to have been born in the United States the person is born in an outlying possession of the United States of parents one of whom is a citizen of the United States who has been physically present in the United States or one of its outlying possessions for a continuous period of one year at any time prior to the birth of such person.
U.S. territories
The Fourteenth Amendment applies to incorporated territories, so people born in incorporated territories of the U.S. are automatically U.S. citizens at birth.