The concept of dual nationality means that a person is a national of two countries at the same time. Each country has its own nationality laws based on its own policy. Persons may have dual nationality by automatic operation of different laws rather than by choice. For example, a child born in a foreign country to U.S. national parents may be both a U.S. national and a national of the country of birth. Or, an individual having one nationality at birth may naturalize at a later date in another country and become a dual national. General information about dual nationality is available here.
U.S. law does not mention dual nationality or require a person to choose one nationality or another. A U.S. citizen may naturalize in a foreign state without any risk to his or her U.S. citizenship. However, persons who acquire a foreign nationality after age 18 by applying for it may relinquish their U.S. nationality if they wish to do so. In order to relinquish U.S. nationality by virtue of naturalization as a citizen of a foreign state, the law requires that the person must apply for the foreign nationality voluntarily and with the intention to relinquish U.S. nationality. Intent may be shown by the person’s statements and conduct.
The naturalization process in Mexico is managed by the Secretaría de Relaciones Exteriores (SRE). There are several methods of naturalizing in Mexico. Generally, Mexican nationality can be acquired by meeting various residency, cultural integration, or marriage requirements. Please contact SRE’s main office for more information on the application procedure.
U.S. nationals, including dual nationals, must use a U.S. passport to enter and leave the United States. Dual nationals may also be required by the foreign country to use its passport to enter and leave that country. Use of the foreign passport to travel to or from a country other than the United States is not inconsistent with U.S. law.