War is not a legal manuever. Soldiers are trained to kill people and break things, not to arrest people and collect evidence. The rules of war are much different than crime fighting, even with legitimate armies that follow "Geneva conventions".
When war involves fighting terrorists who break every known Geneva rule even the Geneva Conventions don't- and shouldn't- apply to or guys.

Now the SCOTUS has changed the rules in the middle of the game, and given terrorists the same rights as US citizens. What SCOTUS did is illegal, not to mention stupid.