The International Committee of the Red Cross 1958 Commentary on IV Geneva Convention Relative to the Protection of Civilian Persons in Time of War Article 4.4 states that "[e]very person in enemy hands must have some status under international law: he is either a prisoner of war and, as such, covered by the Third Convention, a civilian covered by the Fourth Convention, or again, a member of the medical personnel of the armed forces who is covered by the First Convention. There is no intermediate status; nobody in enemy hands can be outside the law. We feel that this is a satisfactory solution – not only satisfying to the mind, but also, and above all, satisfactory from the humanitarian point of view. The ICRC has expressed the opinion that "If civilians directly engage in hostilities, they are considered 'unlawful' or 'unprivileged' combatants or belligerents (the treaties of humanitarian law do not expressly contain these terms). They may be prosecuted under the domestic law of the detaining state for such action".
Article 50 in Chapter II: "Civilians and Civilian Population" of Protocol I Additional to the Geneva Conventions defines that a civilian is not a privileged combatant. Article 51 describes the protection that must be given to civilians (unless they are unprivileged combatants) and civilian populations. Chapter III of Protocol I regulates the targeting of civilian objects. Article 8(2)(b)(i) of the Rome Statute of the International Criminal Court also prohibits attacks directed against civilians. Not all states have ratified Protocol I or the Rome Statute, but it is an accepted principle of international humanitarian law that the direct targeting of civilians is a breach of the customary laws of war and is binding on all belligerents.
Under international maritime law and aviation law a distinction is made between passengers and crew that is similar to that of combatants and civilians under the laws of war. Under their own municipal law governments may extend the definition of who is a civilian to exclude those who work for the emergency services, because members of the emergency services may from time to time need additional legal powers over and above those usually available to ordinary citizens.