How can a person lose their citizenship?

Although Another Country may grant citizenship in their country to a U.S. citizen the U.S. does not recognize or grant dual citizenship. A U.S. citizen "forswears allegiance" to any other power. See: http://www.uscis.gov/portal/site/uscis/menuitem.eb1d4c2a3e5b9ac89243c6a7543f6d1a/?vgnextoid=96719c7755cb9010VgnVCM10000045f3d6a1RCRD&vgnextchannel=96719c7755cb9010VgnVCM10000045f3d6a1RCRD See also: http://www.uscis.gov/portal/site/uscis/menuitem.5af9bb95919f35e66f614176543f6d1a/?vgnextoid=931696981298d010VgnVCM10000048f3d6a1RCRD