I think this is grounds for revoking their citizenship. Is there a law mandating this?
No one is above U.S. law, except the Albanians of course.
There is an interesting case of 3 Albanian-Americans, brothers Bityqi (pron: Beteachi) who illegally entered on Serbia soil and took part in terrorist activities, even admitted it to the media (the pictures of two brothers with sniper rifles are available). They sniped at the Serbian police.
They were detained by Serbian police and shot under unclear circumstances.
However, alhough those 3 Americans have violated both Ameirican and Serbian law, and although there is no Geneva protection for terrorists, spies and sabouteurs, U.S. Ambassador to Belgade call them "victims" and use the 800lbs gorrila power to squeeze Serbian government to "punish the perpetrators" who murdered "American citizens". Seriously.
It is evident that U.S. Ambassador aids and abets terrrorism under the fig leaf of human rights. But who cares, American role in WOT in The Balkans is a joke anyway.
The recent arrest of 6 Albanian-Americans is the rule, not the aberation.