Related Rule
France
Practice Relating to Rule 27. Religious Personnel
France’s LOAC Summary Note (1992) provides:
The specific immunity granted to certain persons and objects by the law of war [including military religious personnel and religious personnel of civilian medical units or civil defence] must be strictly observed … They may not be attacked. 
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, §§ 2.2 and 2.3.
France’s LOAC Manual (2001) states: “The law of armed of conflicts provides special protection for the following persons: … religious personnel attached to armed forces [and] civilian religious personnel”. 
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. 95–96.
France’s Code of Defence (2004), as amended in 2008, states:
Combatants must respect and treat with humanity all persons protected by the applicable international conventions, as well as their objects.
… [R]eligious personnel are protected persons …
Protected persons are protected as long as they abstain from taking a direct part in hostilities.
It is prohibited for combatants to deliberately target protected persons. 
France, Code of Defence, 2004, as amended in 2008, Article D4122-8.