-According to Additional Protocol I to the Geneva Conventions, combatants are:

the armed forces of a party to a conflict, and also groups and units that are under a command responsible to that party for the conduct of its subordinates, even if that party is answerable to a government or an authority not recognized by an adverse party. Such armed forces shall be subject to an internal disciplinary system, which, inter alia, shall enforce compliance with the rules of international law applicable in armed conflict