Dual nationality/citizenship has long been recognized in US law, although not officially favored. Only an overt act and voluntary intention to renounce one's US citizenship before US authorities may trigger the loss of US citizenship rather than the maintenance of one or more nationalities in addition to that of the US. In the 70's, in particular, there was a careful review of whether such overt acts had taken place by a citizen who wished to renew his/her US passport while residing permanently abroad. While there is still some scrutiny, the bigger concern for most potential dual nationals is whether the country of origin has specific laws which strip a citizen of his/her nationality upon taking the oath of citizenship for becoming a US national.
Answered on Jun 07th, 2012 at 12:33 AM