[T]he following acts are and shall remain prohibited at any time and in any place whatsoever with respect to [persons not actively engaged in hostilities]:
(a) violence to life and person, in particular murder of all kinds, mutilation, cruel treatment and torture;
(b) taking of hostages;
(c) outrages upon personal dignity, in particular humiliating and degrading treatment;
(d) the passing of sentences and the carrying out of executions without previous judgment pronounced by a regularly constituted court, affording all the judicial guarantees which are recognized as indispensable by civilized peoples.