Citizenship of the United States
A person who is considered a citizen by more than one nation has "dual citizenship". It is possible for a United States citizen to have dual citizenship; this can be achieved in various ways, such as by birth in the United States to a parent who is a citizen of a foreign country (or in certain circumstances the foreign nationality may be transmitted even by a grandparent) by birth in another country to a parent(s) who is/are a United States citizen/s, or by having parents who are citizens of different countries. Anyone who becomes a naturalized U.S. citizen is required to renounce any prior "allegiance" to other countries during the naturalization ceremony; however, this renunciation of allegiance renunciation of citizenship to those countries.
Relinquishment of United States nationality
In the early 20th century, the State Department and the Immigration and Naturalization Service clashed on the question of whether parental action could result in loss of citizenship of minor children. Though the Attorney-General favored the State Department's view that it could, in 1939 the Supreme Court held in "Perkins v. Elg" that a citizen born in the U.S. did not lose her own citizenship when her parents, both naturalized Americans of Swedish origin, returned to Sweden and her father renounced his American citizenship. In the 2010s, the U.S. Consulate in Calgary ruled that Carol Tapanila, an American-born Canadian woman who had renounced her own U.S. citizenship, could not renounce on behalf of her developmentally disabled son; the son was also ruled unable to renounce on his own due to his inability to understand the concept of citizenship or renunciation, thus leaving him permanently subject to U.S. taxation on gains in his Canadian government-funded Registered Disability Savings Plan.