Related Rule
France
Practice Relating to Rule 3. Definition of Combatants
France’s LOAC Summary Note (1992) and LOAC Teaching Note (2000) provide that all members of the armed forces, other than medical and religious personnel, are combatants. 
France, Fiche de Synthèse sur les Règles Applicables dans les Conflits Armés, Note No. 432/DEF/EMA/OL.2/NP, Général de Corps d’Armée Voinot (pour l’Amiral Lanxade, Chef d’Etat-major des Armées), 1992, § 1.2; Fiche didactique relative au droit des conflits armés, Directive of the Ministry of Defence, 4 January 2000, annexed to the Directive No. 147 of the Ministry of Defence of 4 January 2000, p. 2.
France’s LOAC Manual (2001) defines combatants with reference to Article 4(A) of the 1949 Geneva Convention III. 
France, Manuel de droit des conflits armés, Ministère de la Défense, Direction des Affaires Juridiques, Sous-Direction du droit international humanitaire et du droit européen, Bureau du droit des conflits armés, 2001, p. 39; see also pp. 70–71.
Under the heading “Guerrilla”, the manual restates, inter alia, Article 4(A)(2) of the 1949 Geneva Convention III and provides: “Permitted to fight and to obtain the status of prisoner of war in the case of capture are resistance fighters, militias and volunteer corps who are not part of the regular army but who respond to the definition [therein].” 
France, Manuel de droit des conflits armés, Ministère de la Défense, Direction des Affaires Juridiques, Sous-Direction du droit international humanitaire et du droit européen, Bureau du droit des conflits armés, 2001, pp. 70–71.
Under the heading “Resistance”, the manual restates Article 4(A)(2) of the 1949 Geneva Convention III and further provides:
Inherited from World War II, this term refers to activities carried out against occupation forces and inspired by guerrilla techniques. The “resistance fighters” have combatant status on condition they respect the provisions of Article 4 of the Geneva Convention III of 12 August 1949 relative to the Treatment of Prisoners of War, above. At the moment when they act, and whatever the circumstances, the members of a resistance movement must take all necessary measures to distinguish themselves clearly from the civilian population. 
France, Manuel de droit des conflits armés, Ministère de la Défense, Direction des Affaires Juridiques, Sous-Direction du droit international humanitaire et du droit européen, Bureau du droit des conflits armés, 2001, pp. 110–111.