- Under the U.S. Constitution, anyone born in the United States automatically becomes a U.S. citizen (those born in U.S. territories such as American Samoa are U.S. nationals, but not necessarily citizens). In addition, children born abroad to two U.S. citizen parents are citizens at birth. Children born abroad to one U.S. citizen parent can apply for automatic U.S. citizenship if the requirements of the Child Citizenship Act of 2000 are met (see References below).
- A non-U.S. citizen may become a naturalized U.S. citizen if he obtains lawful permanent residence in the United States and completes naturalization requirements. A naturalized U.S. citizen is considered equal to other U.S. citizens except in two respects--a naturalized U.S. citizen's citizenship can be revoked if it is later found to have been obtained through fraud, and a naturalized U.S. citizen cannot serve as president of the United States.
- Generally, a non-U.S. citizen must have legally resided in the United States for at least five years before applying for U.S. citizenship (this minimum is reduced to three years for those married to U.S. citizens). Absence from the United States for more than six months during this period will endanger eligibility for citizenship, as will cumulative absences of 30 months of more. An applicant for citizenship must also have resided in the same state or district for at least three months immediately prior to applying for U.S. citizenship.
- Applicants for U.S. citizenship must demonstrate rudimentary knowledge of the English language (some exceptions apply), as well as basic knowledge of U.S. history and the U.S. political system. A written test is administered to verify this knowledge.
- Applicants for U.S. citizenship must demonstrate good moral character during their period of residency in the United States. Involvement in prostitution, illegal drug use, polygamy, illegal gambling and immigration fraud, among other offenses, will render the applicant ineligible. The final step in the acquisition of U.S. citizenship is to take the Oath of Allegiance, in which the applicant swears loyalty to the Constitution and laws of the United States, agrees to serve in the U.S. military if required, and renounces foreign allegiances (this does not prevent dual citizenship; see Section 7 below).
- U.S. citizenship can be renounced before a consular officer at a U.S. embassy or consulate abroad (and in certain cases within the United States). It is also possible to impliedly renounce U.S. citizenship through treason, by serving in the armed forces of a foreign country, by accepting employment with a foreign government, and by becoming a citizen of another nation (in all of these cases, citizenship will not be lost as long as the citizen did not actually intend to renounce her U.S. citizenship by performing the act).
- The United States allows its citizens to be citizens of other countries at the same time, although most other nations do not recognize dual citizenship. Consequently, a dual citizen may find it difficult to obtain U.S. consular protection while in the other country that has granted her citizenship.
