Legally, these guys are non-lawful enemy combatants. They have put themselves in a legal grey area, not by committing crimes, but by committing acts of war. Many, if not all of them have been trained, if captured, to try to disrupt the legal system by any means necessary. They are fighting a war.
According to the US Constitution, it is Congress that establishes courts (except the supreme court) and decides what their purpose is. The President does not get to decide this. Military commissions have been accordingly established by Congress to try the detainees. The current President halted this process. Thus the detainees are in legal limbo until either Congress establishes a different court to hear the cases or the President decides to comply with the current law.
Here is what happened to some German non-lawful combatants during WWII: http://en.wikipedia.org/wiki/Operation_Pastorius
About 1/3 of detainees released have gone right back to the fighting: http://www.longwarjournal.org/archives/2012/03/latest_gitmo_...
And these were the low risk ones.
According to the US Constitution, it is Congress that establishes courts (except the supreme court) and decides what their purpose is. The President does not get to decide this. Military commissions have been accordingly established by Congress to try the detainees. The current President halted this process. Thus the detainees are in legal limbo until either Congress establishes a different court to hear the cases or the President decides to comply with the current law.