Now *there's* something I can never imagine doing. Wow.
ANYWay...
Although current US law forbids the government from taking your citizenship from you against your will, it does permit you to give it up voluntarily. This has placed the US State Department in the complex position of determining whether someone who claims to be a US citizen has, in fact, given up that citizenship by his voluntary statements or actions.
In the early days of court-mandated acceptance of dual citizenship, State Department officials (hostile as most of them were to the whole idea of dual citizenship) tended to play hardball with people who claimed dual status, looking for almost any excuse to revoke US citizenship, and frequently ruling that a person had voluntarily forsaken his US ties despite steadfast protestations or even convincing evidence to the contrary.
On 16 April 1990, though, the State Department adopted a new set of guidelines for handling dual citizenship cases which are much more streamlined and liberal than before.The State Department now says that it will assume that a US citizen intends to retain (not give up) his US citizenship if he: 1. is naturalized in a foreign country;
2. takes a routine oath of allegiance to a foreign country; or
3. accepts foreign government employment that is of a "non-policy-level" nature.
Apparently, a "routine oath of allegiance" to another country is no longer taken as firm evidence of intent to give up US citizenship, even if said oath includes a renunciation of US citizenship. This represents a dramatic reversal of previous US policy; it used to be that any such statement was taken rigidly at face value (as in the Supreme Court's 1980 Terrazas decision).
This presumption that someone intends to keep US citizenship does not apply to a person who: 1. takes a "policy-level" position in a foreign country;
2. is convicted of treason against the US; or
3. engages in "conduct which is so inconsistent with retention of U.S. citizenship that it compels a conclusion that
intended to relinquish U.S. citizenship."
The State Department says that cases of these kinds will be examined carefully to determine the person's intent. They also say that cases falling under the last criterion mentioned above (conduct wholly inconsistent with intent to keep US citizenship) are presumed to be "very rare."
http://www.richw.org/dualcit/faq.html#losing