His terrorist conspiracy was enacted here. We would be insane to allow him to serve his sentence elsewhere, especially when Euro-weenies such as the French will allow him all sorts of visitations and benefits to make his sentence more palatable, and would very likely commute that sentence after some minimal period of time (I can easily imagine the 'movement' on his behalf in a few years "Alors, Monsieur Moussaoui, he did not actually kill anyone, zeee poor man has suffered enough and his dear maman wants him home!"). Even if by some miracle the French would keep him locked away (and we cannot possibly rely upon any assurances to that effect), he does not deserve the benefit of being closer to friends and family, enjoying visitations, etc.
Lock the scumbag in a supermax hole and let him rot forever.
It may be a treaty issue.
However I don't think it will really get far.
The only way is if the state department does this as a way to embarrase the president.
BEWARE THE BUREACRATS OF THE STATE DEPARTMENT!