One may need to pay attention not to confuse the issue of Guantanamo as that of being about the location of the prison in itself. The problem with being outside the country is that a different standard of justice is allowed there. Justice is something one need to seek at the best level he can and is not something that one can fashion to his taste. Therefore there should be one standard of justice at least from the entity making of the standard.
However, I emphasise again, that prison is much better than forcing expelling the residents to worse places.