Related Rule
France
Practice Relating to Rule 65. Perfidy
Section B. Killing, injuring or capturing an adversary by resort to perfidy
France’s LOAC Manual (2001) states: “It is prohibited to injure, kill or capture [an adversary] by resort to perfidy.” This may constitute a war crime. 
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. 47; see also p. 85.
France’s Penal Code (1992), as amended in 2010, states in its section on war crimes related to international armed conflict:
Making improper use of the flag of truce, of the flag or of the military insignia and uniform of the enemy or of the United Nations, as well as of the distinctive emblems provided for under the 1949 Geneva Conventions and their [1977] Additional Protocols, and thereby causing serious bodily harm to a combatant from the adverse party is punishable by 20 years’ imprisonment.
When the offence defined in the first paragraph results in such harm to the combatant leading to permanent mutilation or disability, the penalty is increased to 30 years’ imprisonment.
When the offence results in the death of the victim, the penalty is increased to life imprisonment. 
France, Penal Code, 1992, as amended in 2010, Article 461-29.