The Constitution guarantees everybody in this country due process of law, including the right of habeas corpus. This combatant, like any other citizen, is taking full advantage of that:
Jose Padilla v. U.S.
BTW, where is that Petition for the Great Writ sitting right now? In the same situation as Padella. I would bet that if this was the son of some rich guy this petition would be fast tracked in warp speed.