Prohibited conduct:
“(D) Murder.—
The act of a person who intentionally kills, or conspires or attempts to kill, or kills whether intentionally or unintentionally in the course of committing any other offense under this subsection, one or more persons taking no active part in the hostilities, including those placed out of combat by sickness, wounds, detention, or any other cause”
-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
According to this rule, when military medical and religious personnel are members of the armed forces, they are nevertheless considered non-combatants. According to the First Geneva Convention, temporary medical personnel have to be respected and protected as non-combatants only as long as the medical assignment lasts (see commentary to Rule 25).[14] As is the case for civilians (see Rule 6), respect for non-combatants is contingent on their abstaining from taking a direct part in hostilities.
The military manuals of Germany and the United States point out that there can be other non-combatant members of the armed forces besides medical and religious personnel. Germany’s Military Manual explains that “combatants are persons who may take a direct part in hostilities, i.e., participate in the use of a weapon or a weapon-system in an indispensable function”, and specifies, therefore, that “persons who are members of the armed forces but do not have any combat mission, such as judges, government officials and blue-collar workers, are non-combatants”.[15] The US Naval Handbook states that “civil defense personnel and members of the armed forces who have acquired civil defense status” are non-combatants, in addition to medical and religious personnel.[16]
Non-combatant members of the armed forces are not to be confused, however, with civilians accompanying armed forces who are not members of the armed forces by definition.[17]
18 U.S. Code § 2441 - War crimes
Prohibited conduct: “(D) Murder.— The act of a person who intentionally kills, or conspires or attempts to kill, or kills whether intentionally or unintentionally in the course of committing any other offense under this subsection, one or more persons taking no active part in the hostilities, including those placed out of combat by sickness, wounds, detention, or any other cause”
https://www.law.cornell.edu/uscode/text/18/2441