The whole point of Guantanamo was to get around established laws, it should never have been used for prisoners. The prisoners should be treated as POWs per the Geneva conventions, given a legitimate trial in the USA or set free. I don't buy the arguments that we need a special category of criminal/combatant so the established laws can be circumvented. Obama should have used an executive order to move the prisoners to the USA and put them on trial as he (supposedly) originally intended to do.
By the way, there is good reason to believe that some of the prisoners may be innocent, or too small-time to be worth incarcerating.