IIRC, Guantanimo bay is out side the usual legal US juristiction, as a result they employed more extreme interrogation techniques such as waterboarding (a form of torture under international law) to obtain information from the inmates the camp was designed for.
If this is still the case, how are these people going to be treated, they are not terrorists, just perhaps in the US without the correct paperwork. This is not a reason to treat people in a inhumane way, which is not acceptable.
I would also suspect countries could be held accountable if people deported to the USA end up treated badly.