Based on the U.S. Department of State regulation on dual citizenship (7 FAM 1162), the Supreme Court of the United States has stated that dual citizenship is a "status long recognized in the law" and that "a person may have and exercise rights of nationality in two countries and be subject to the responsibilities of both. The mere fact he asserts the rights of one citizenship does not, without more, mean that he renounces the other", Kawakita v. U.S., 343 U.S. 717 (1952). In Schneider v. Rusk, 377 U.S. 163 (1964), the U.S. Supreme Court ruled that a naturalized U.S. citizen has the right to return to his native country and to resume his former citizenship, and also to remain a U.S. citizen even if he never returns to the United States.
The Immigration and Nationality Act (INA) neither defines dual citizenship nor takes a position for it or against it. There has been no prohibition against dual citizenship, but some provisions of the INA and earlier U.S. nationality laws were designed to reduce situations in which dual citizenship exists. Although naturalizing citizens are required to undertake an oath renouncing previous allegiances, the oath has never been enforced to require the actual termination of original citizenship.
Although the U.S. government does not endorse dual citizenship as a matter of policy, it recognizes the existence of dual citizenship and completely tolerates the maintenance of multiple citizenship by U.S. citizens. In the past, claims of other countries on dual-national U.S. citizens sometimes placed them in situations where their obligations to one country were in conflict with the laws of the other. However, as fewer countries require military service and most base other obligations (such as the payment of taxes) on residence and not citizenship, these conflicts have become less frequent.
A U.S. citizen may lose his or her dual citizenship by obtaining naturalization in a foreign state, by taking an oath or making an affirmation or other formal declaration of allegiance to a foreign state or political subdivision thereof, by serving in the armed forces of a foreign state, or by performing certain other acts, but only if the act was performed "voluntarily and with the intention to relinquish U.S. nationality".