John McCain, having served in Vietnam and having been subjected to needless torture, passionately argues that torture, even in war-time, ought to be illegal, at least for the U.S., which aspires to be held to a higher standard.
On the other hand, if my POW is likely to know stuff that my side can profit from, and if torture seems like a good way to obtain that information, is not failure to torture the greater evil if he does not tell me what I want to know without the use of torture?
On the other hand, if my POW is merely a soldier who was drafted or volunteered because it was a patriotic duty, iow, if there is reason to believe that he probably wouldn't be privy to important information, well, then, that POW ought to be protected from random acts of torture. And indeed, he is protected by international law, which ought to constrain our soldiers from illegal acts of torture.
On the other hand, if my POW is not a citizen of my country -- and why would he be? -- why ought he be protected by laws that protect our own citizens from our own state? If my POW was a U.S. citizen who ran to fight for the other side, his act was an act of renunciation og his homeland and he ought not to be entitled to any privileges that might otherwise protect a citizen. If my POW is a soldier of an army that counts only fanatics who are all personally forsworn to destroy the enemy (like al Qaeda), not merely patriots or even soldiers of fortune, that soldier ought not to be entitled to the same protections guaranteed by international law regarding the rights of combatants. What do we do while we wait for international law to catch up with modern hatred? Good question.
What then ought we to do? Sometimes, what is called for is judgment, and the consequences of that judgment, right or wrong. It is the first obligation of an American soldier to protect his country. If torture proves to protect his country, then our commander is in the right to use it. If the torture proves fruitless, our commander may be held liable of ignoring the international rights of a combatant. In any case, an American soldier who is not a commander who, on his own, initiates torture is immediately guilty of breaking the laws of warfare and must be held accountable.
On the other hand, International Law needs to take into account a new reality: there are soldiers who serve at the pleasure of their country, with a very wide range of complicity, and there are soldiers who are fanatical jihadists. These new soldiers have committed their lives to destroy those they consider their enemy. They are personally beholden to an ideal of killing others. They ought to be treated differently from an "old-fashioned" soldier who was just doing his patriotic duty and may even have served only under duress. They ought to be killed, before they kill us.
Some issues are just not easy.
By the way, there is one group, a sizable group, of home-grown American jihadists, although they are not known by that name, who will, in time, prove as dangerous as al Qaeda. But that story is for another time.