Under law, there's no such a thing as 'war', there are armed conflicts. It is also incorrect that armed conflicts can only happen between states, there are international, non-international conflicts and there are other situations of armed violence. And there are different level of international and human rights law that apply different depending on the type of conflict. There's also parts of tne resolutions that state that it doesn't matter what you call them, they're still POW and you still have to treat them as such. The real problem is that the US hasn't ratified any of those resolutions and conventions because they fear having any diplomatic oversight, the US has committed so many war crimes that it would take decades of research just to sort out the last half of the 20th century.

Finally, even if international humanitarian law doesn't apply, then international human rights law still does. But the US plays with rules based international order as their toy because they have the biggest guns and it is hard to front them. And before any of the what abouters comes here to reply, Russia and China are just as bad. No international neocolonialist empire is free of human rights violations.