"Many Americans, even lawyers, are misinformed about the U.S. citizenship naturalization process, says San Diego Immigration lawyer Robert Martino.
Perhaps the biggest myth is that the country does not recognize dual citizenship. In fact, those who take the oath of citizenship in this country are required to renounce all allegiances to foreign governments. However, some countries do not recognize this renunciation and are willing to continue to extend the benefits of citizenship in the home country to the naturalized American.
As for native-born Americans who become citizens of another country, the State Deparment requires a showing that the Americans intended to lose their U.S. citizenship. Committing an act of expatriation, such as joining a foreign military or becoming an official in a foreign government, among other things, is seen as evidence that the former American intends to renounce U.S. citizenship."
ABA Journal, September 2002, p. 40. Sources: U.S. Department of Justice, Bureau of INS web site
www.ins.usdoj.gov and U.S. Immigration and Citizenship, Revised Edition, by Allan Wernick, Prima Publishing, New York, 2002.