The laws of war. They were passed by congress in the 1700s, and have been used in all wars we have been in.
They are directly under the executive branch, and not under the judicial.
After WW2, the Chief Justice of the United States presided over the Military Tribunal at Nuremberg.
They implemented the Laws of War. That is what Congress just authorized for use in the Military Tribunals for Club Gitmo.
The Laws of War do not include the Bill of Rights, or Habeas Corpus. It is Martial Law. (When you hear of a Governor declaring "Martial Law" what do think they are declaring?)
It is not a violation for either the Civil Law or UCMJ for enemy combatants, spies, and so forth to attack the United States troops.