(1) Persons taking no active part in the hostilities, including members of armed forces who have laid down their arms and those placed ' hors de combat ' by sickness, wounds, detention, or any other cause, shall in all circumstances be treated humanely, without any adverse distinction founded on race, colour, religion or faith, sex, birth or wealth, or any other similar criteria. To this end, the following acts are and shall remain prohibited at any time and in any place whatsoever with respect to the above-mentioned persons:
So how in God's name does this apply to non-uniformed terrorists? Once again, the Supreme Court finds a penumbra.
And, moreover, have said terrorists (uniformed or not uniformed) signed this Geneva Treaty - that is, are they now being recognized as a nation-state? [Quick answer: No.]
So, no rights under the US Constitution for those who are non-US citizens; and no rights under this Geneva Treaty as a non-signatory.
Or ... is this now the beginning of "World Government" in earnest via the back-door?
Anyone at Gitmo is "taking no active part in the hostilities", and hence is a person who "shall in all circumstances be treated humanely".
Article 3 doesn't restrict itself to only uniformed people, or only conventional soldiers, or any other similar group. Anyone who isn't fighting is covered, lawful combatant or otherwise.
Whether you think this is a good idea or even whether this will represent a significant change is another matter, but I'm pretty sure that's why this applies to all prisoners held by the US.