basicly if the gov dosnt like you they can classifie you as an "enemy combatant" and imprison you for as long as they want while they think up ways to charge you.
the gov can't really characterize you as an enegy combatant willy nilly, there are review boards and such. If you are an american citizen, you also have all fo your judicial rights (does that include the clisifed evidence stuff?) intact. If you live in a 1st world nation the US has a treaty w/ ur country, so i highly doubt that the US would cause an internationnal incident to arrest u as an enemy combatant.