Expatriation is the voluntary act of abandoning the nationality or citizenship of a country. Any citizen, regardless of whether citizenship was acquired at birth or by later naturalization, can expatriate themselves from the United States by committing any act enumerated in Section 349 of the Immigration and Nationality Act (INA), as long as the act is committed voluntarily and with the specific intention of transferring allegiance from the United States.
The commission of any of the acts in Section 349 creates a presumption of having been committed voluntarily, but the presumption is rebuttable upon a showing, by preponderance of the evidence, that the act was not done voluntarily.
The following is a brief overview of the acts which may result it expatriation.
1.    Naturalization in a Foreign State
Obtaining naturalization in a foreign state will result in expatriation. The naturalization must be upon the person’s own application or upon the person’s duly authorized agent’s application. It is important to distinguish here that this section does not always preclude dual nationality, for more information on dual nationality, click here [provide link to article on dual nationality].
2.    Oath, affirmation, or Other Declaration of Allegiance to a Foreign State
Taking an oath, affirmation, or other formal declaration of allegiance to a foreign state or its political subdivisions will likewise result in expatriation.
3.    Joining the Armed Forces of a Foreign State
Anyone who enters or serves in the armed forces of a foreign state as a commissioned or non-commissioned officer will be subject to expatriation. Also, anyone who enters or serves in the armed forces, in any capacity, of a foreign state which is engaged in hostilities with the United States will be subject to expatriation.
4.    Employment Under the Government of a Foreign State
The act of accepting, serving in, or performing the duties of any office, post, or employment under the government of a foreign state is grounds for expatriation if the office, post, or employment is conditioned upon acquiring the nationality of the foreign state or upon taking an oath, affirmation, or declaration of allegiance.
5.    Formal Renunciation
In a Foreign State. A person may formally renounce his or her U.S. nationality by making such renunciation before a diplomatic or consular officer of the United States in a foreign state, so long as the renunciation is effected in accordance with the manner prescribed by the Secretary of State (currently this is accomplished by signing an oath of renunciation). Parents cannot renounce U.S. citizenship on behalf of their children.
Renunciation of citizenship is irrevocable, except in the case of a person who renounced their citizenship before they were eighteen years of age, as long as the person, within six months of turning eighteen, makes known their desire to have their citizenship reinstated.
In the United States. A person may also formally renounce his or her citizenship by making the renunciation before an officer designated by the Attorney General, but only when the United States is in a state of war and the Attorney General determines that the renunciation is not contrary to the interests of national defense.
6.    Treason
A conviction for an act of treason, attempting to overthrow the U.S. government, bearing arms against the United States, and like offenses against the United States will result in expatriation.