Attempts to simplify ethics in war by claiming exclusive legitimate authority for the law of armed conflict underestimate the moral complexities facing soldiers. Soldiers risk wrongdoing if they refuse moral guidance that can independently evaluate their legal permissions. State soldiers need to know when to object to a legal duty to fight; nonstate fighters need to know when to disregard legal prohibitions against fighting. And both might sometimes best discharge their moral duties by following a bespoke rule departing from noncombatant immunity in a principled way that has been designed for a particular conflict by an authoritative leadership.
Finlay, C. J. (2019). Justification and Legitimacy at War: on the Sources of Moral Guidance for Soldiers. Ethics: An International Journal of Social, Political, and Legal Philosophy, 129(4), 576-602. https://doi.org/10.1086/702973