This is a genuine request for a factual answer, not for debate about the
rights and wrongs of the situation.
Assuming that the prisoners held in Guantanomo bay can be shown to have
associated / trained with Al Qaeda, what charges would they be facing
Does the US Military have the power to invent new charges, and then apply those charges to the prisoners?
I am not an expert, and this is a darn tricky subject, but well worth consideration.
First off, it is no crime to fight the Americans. If these guys fought honorably and according to the rules, they are POWs. POWs don’t get trials as they are not being punished (just kept out of circulation) and committed no crime. The US would not try them and it would be morally wrong for the Afghans to do so.
But just the act of fighting the Americans does not make you immune to the law. If these guys fought the Americans in uniform and under centralized command, they could be tried for crimes they may have committed (like a bank robbery for profit). This trial could be done by the detaining power or its Afghan ally.
If they fought the Americans but did not observe the rules, then they are not legal combatants. Just thugs. If they did not play by the rules they are not protected by them. In this case an un-uniformed freelance fighter who is captured could be tried by the detaining power or the Afghanis.
However, the rules say that if a person is detained and you are not sure if he deserves the protections offered by the rules and customs you must presumptively give him the highest level of protection until a hearing by the detaining power can clarify his status.
That is to say they must be treated as POWs until a hearing shows they are unworthy of those protections.
So, the first step is for the Americans to conduct hearings to determine the status of these fine fellows. The honest fighters will be detained until the war is over. They will not be tried. The criminals will be tried by the detaining power under the same rules and protections offered to its own soldiers and punished as its own soldiers would be. (Or in an Afghani court under Afghan law.)
That should get us started on this issue.
The awkward situation that the Americans have got themselves into re. the British prisoners is that it’s 100% clear that if they were charged with any offence in a UK court, the case would be thrown out due to the ill-treatment during captivity and the unnreliable and unfair gathering of evidence.
Yes, but…
Although some of the detainees are British subjects, that does not obligate the Americans to hand them over to British courts.
If they are held as POWs then they will not be handed over as they will not be charged and will simply be detained until the war is over. Under this scenario, they will not be charged with a crime, nor will they be punished, just detained.
If the Detaining Power finds them to be unworthy of the protection of the Usages and Customs of War, they can then be tried by the Detaining Power or handed over to someone else.
If these British subjects are tried under US law, they will have the protections those laws offer. If they are tried in Afghanistan, those laws would apply. On the face of it, British courts would lack jurisdiction to try a person for a crime that may have occurred in another country. (Exceptions might be the Prevention of Terrorism Act or perhaps the Espionage Act.)
It is not clear to me what an illegal combatant captured in Afghanistan by the Americans could be tried for under British law.