I'm trying to come up with a way and reason that either The Hague Treaties of 1907 or the Geneva Conventions of later times could include irregulars in the rules of war. I'm looking for a way to have "terrorists" or "Freedom Fighters" be given the rights of POW's, provided they limit their attacks to legitimate targets, and have a declared agenda. Example: French underground blows up civilian passenger train...criminal act. IRA bombing of a pub...criminal action. IRA shoots military forces...legitimate act of war.
Could such a treaty have been put into effect at any time? And could it make irregular warfare not as hard on the civilian non-combatants?