Survey of the Law of Expatriation

Expatriating a U.S. citizen subject to the Citizenship Clause of the Fourteenth Amendment on the ground that, after reaching the age of 18, the person has obtained foreign citizenship or declared allegiance to a foreign state generally will not be possible absent substantial evidence, apart from the act itself, that the individual specifically intended to relinquish U.S. citizenship. An express statement of renunciation of U.S. citizenship would suffice.

An intent to renounce citizenship can be inferred from the act of serving in the armed forces of a foreign state engaged in hostilities against the United States.