Sorry, they are combattants.
Combattants can be held without trial until the end of hostilities. In other words until the USA and Al Qaeda either sign a deal or one exterminates the other, these guys can be held indefinitely -- forever. They have no right to trial simply because they are not being charged with any crimes. Even if they were charged and acquited of war crimes, the USA still would not need to release them. I know that it is a large loophole in International Law, but it is there.
In summer of 1945, the USA had some six million German, Japanese, and Italian prisoners in huge prison camps in Oklahoma and Texas. None of them were released until the war was OVER. There was no need to charge them with anything.