I managed to miss this article in the New York Times, which reports that the Obama administration has added Anwar al-Awlaki to its assassination-by-drone list. Awlaki is a radical muslim cleric who is apparently hiding in Yemen and is charismatic enough to have inspired a number of terrorist plots, including the attempted Times Square bombing. He's also a U.S. citizen. Actually, let me fix that. He's also a U.S. citizen who has now been targeted for assassination without any due process of law.
use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons, in order to prevent any future acts of international terrorism against the United States by such nations, organizations or persons.The wiggle room comes, I guess, with the word "aided". But, still, none of that matters relative to the rights to due process granted U.S. citizens. It is, of course, possible to lose one's citizenship for committing acts of treason-- but even that requires a conviction (ie, a legal process).