This was hashed out long ago. Again, from Wikipedia:
“The term unlawful combatant has been used for the past century in legal literature, military manuals and case law.[3] The term “unlawful combatants” was first used in U.S. municipal law in a 1942 United States Supreme Court decision in the case Ex parte Quirin.[28] In this case, the Supreme Court upheld the jurisdiction of a U.S. military tribunal over the trial of eight German saboteurs in the U.S. during World War II. This decision states:
By universal agreement and practice, the law of war draws a distinction between the armed forces and the peaceful populations of belligerent nations and also between those who are lawful and unlawful combatants. Lawful combatants are subject to capture and detention as prisoners of war by opposing military forces. Unlawful combatants are likewise subject to capture and detention, but in addition they are subject to trial and punishment by military tribunals for acts which render their belligerency unlawful. The spy who secretly and without uniform passes the military lines of a belligerent in time of war, seeking to gather military information and communicate it to the enemy, or an enemy combatant who without uniform comes secretly through the lines for the purpose of waging war by destruction of life or property, are familiar examples of belligerents who are generally deemed not to be entitled to the status of prisoners of war, but to be offenders against the law of war subject to trial and punishment by military tribunals.”
Note well the sentence: “Unlawful combatants are likewise subject to capture and detention, but in addition they are subject to trial and punishment by military tribunals for acts which render their belligerency unlawful.”
Other than a Bush-era executive order, I don't know of any justification for torture of an enemy by U.S. forces.
Under the circumstances, Bush can be pardoned, or maybe just censured, for his administration's limited use of waterboarding.
The real problem is the slippery slope. Just 15 years after 9/11 voters are considering giving torture powers to either a radical Marxist like Clinton, or an idiot like Trump.
Other than a Bush-era executive order, I don't know of any justification for torture of an enemy by U.S. forces.
As I pointed out in post 15, equivocating on the word "torture" does not make a valid argument. Either by "torture" you mean anything that an enemy may not happen to like, such as being kept in captivity (which as an aside included very awful conditions in the civil war), or you mean something they do not like that is so awful that it must never ever be done even as punishment to an unlawful combatant in a case that could save innocent life. In the first case, other Presidents have authorized torture. If the second then you have the burden to show why its so awful to do to the terrorists when we even used to do it to our own elite soldiers in training. Or if you think that it is somewhere in between it still falls short of the second case, and thus your argument is in ruins because the second case is exactly what you must show. And I am too smart to be fooled by equivocations. Sorry ;-).