A few legal misunderstandings I’ve seen in this thread:
It is not true that conditions of confinement can never be legally considered punishment. For pre-trial conditions challenges, see Turkmen v. Ashcroft, 2006 WL 1662663 (EDNY 2006) (stating the Fifth Amendment standard for when conditions of confinement are considered punishment.)) For post-trial, see Wilson v. Seiter, 111 S. Ct. 2321, 2327 (1991) (setting out the Eighth Amendment standard.) So it is not the case that as a matter of the scope of the Fifth or Eighth Amendments that torture can never be punishment–it can be if it is intended to punish, and it is clear from many of the FOIA documents that at least in some cases this is the intention.
Those citing Eisentrager seem to be assuming that it is still good law on this issue. As the court said in Rasul, “Petitioners in these cases differ from the Eisentrager detainees in important respects: They are not nationals of countries at war with the United States, and they deny that they have engaged in or plotted acts of aggression against the United States; they have never been afforded access to any tribunal, much less charged with and convicted of wrongdoing; and for more than two years they have been imprisoned in territory over which the United States exercises exclusive jurisdiction and control.” Those distinguishing characteristics are also true of, say, detainees in Abu Ghraib.
The Constitution can indeed extend beyond our borders if those detainees have a procedural way to get into court. As the court also noted in Rasul, "In Braden v. 30th Judicial Circuit Court of Ky., 410 U. S. 484, 495 (1973), this Court held, contrary to Ahrens, that the prisoner’s presence within the territorial jurisdiction of the district court is not “an invariable prerequisite” to the exercise of district court jurisdiction under the federal habeas statute. Rather, because “the writ of habeas corpus does not act upon the prisoner who seeks relief, but upon the person who holds him in what is alleged to be unlawful custody,” a district court acts “within [its] respective jurisdiction…”
Of course, Rasul did not need to directly overrule Eisentrager because they found that the habeas statute provided for relief, but Boumediene might. The argument that the Constitution might apply to some of those under our control and jurisdiction in another country deserves more serious consideration than it has been given in this thread.
Now, the fact that conditions of confinement can equal punishment and habeas can be brought by aliens abroad does not mean that aliens abroad can bring habeas actions for torture. Generally habeas is about challenging the basis for detention. But I think this focuses the debate a little and moves past some of the falsehoods being propagated.