Through birth abroad to two United States citizens
See also: jus sanguinis
In most cases, one is a U.S. citizen if both of the following are true:
Both parents were U.S. citizens at the time of the child's birth
At least one parent lived in the United States prior to the child's birth.
INA 301(c) and INA 301(a)(3) state, "and one of whom has had a residence." The FAM (Foreign Affairs Manual) states "no amount of time specified."
A person's record of birth abroad, if registered with a U.S. consulate or embassy, is proof of his or her citizenship. He or she may also apply for a passport or a Certificate of Citizenship to have his or her citizenship recognized.
[edit] Through birth abroad to one United States citizen
For persons born on or after November 14, 1986, a person is a U.S. citizen if all of the following are true:[4]
One of the person's parents was a U.S. citizen when the person in question was born;
The citizen parent lived at least 5 years in the United States before his or her child's birth;
A minimum of 2 of these 5 years in the United States were after the citizen parent's 14th birthday.
A person's record of birth abroad, if registered with a U.S. consulate or embassy, is proof of his or her citizenship. Such a person may also apply for a passport or a Certificate of Citizenship to have a record of his or her citizenship. Such documentation is often useful to prove citizenship in lieu of the availability of an American birth certificate.
Different rules apply for persons born abroad to one U.S. citizen before November 14, 1986. United States law on this subject changed multiple times throughout the twentieth century, and the law as it existed at the time of the individual's birth