those combatants can receive due process - through military tribunal - no one is arguing that Padilla should be held forever without due process.
the courts on the other hand - are even looking to extend these rights to NON-CITIZENS. Should Khallid Sheik Mohammed have any rights in the US civilian court system?
A legitimate issue for the Supreme Court is whether or not a military tribunal for a civilian constitutes due process. The Court has not ruled on this particular set of facts (US citizen captured in the US) but the Bush Administration doesn't appear to want to take the chance the Court might see things differently.