Related Rule
France
Practice Relating to Rule 156. Definition of War Crimes
France’s LOAC Summary Note (1992) gives a detailed list of war crimes and provides: “Grave breaches of the law of war are war crimes.” 
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, § 3.4.
France’s LOAC Teaching Note (2000) states: “very grave breach of the rules of the law of armed conflicts represents a war crime.” 
France, 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. 7.
France’s LOAC Manual (2001), under the heading “War crimes”, cites, inter alia, Article 212(1) of the French Penal Code (which provides for life imprisonment for such acts as deportation, enslavement, massive and systematic summary executions, abductions of persons followed by their disappearance, torture and inhuman acts) and Article 75 of the 1977 Additional Protocol I. It also refers to Articles 41 and 56 of the 1907 Hague Regulations, Articles 3, 49 and 50 of the 1949 Geneva Convention I, Articles 3, 50 and 51 of the 1949 Geneva Convention II, Articles 3, 80–88, 105–108, 129 and 130 of the 1949 Geneva Convention III, Articles 3, 146 and 147 of the 1949 Geneva Convention IV and Articles 11, 75 and 85 of the 1977 Additional Protocol I. The manual further states:
Article 8 of the [1998 ICC Statute] defines as war crimes “grave breaches of the Geneva Conventions of 12 August 1949, [committed] against persons or property protected under the provisions of the relevant Geneva Convention” and “grave breaches of the laws and customs of war in an international or non-international armed conflict”. 
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. 44–46.
France’s Ordinance on Repression of War Crimes (1944), relating to offences committed during the Second World War, provided for the prosecution of:
enemy nationals or non-French agents … guilty of crimes or offences committed since the opening of hostilities either in France or in a territory under French authority, either against a French national or a person protected by France, a soldier serving or having served under the French flag, a stateless person residing on French territory … or a refugee on French territory, or to the prejudice of the property of any of these persons mentioned above and of any French legal entity, provided that these offences, even if committed at the occasion or under the pretext of the state of war, are not justified by the laws and customs of war. 
France, Ordinance on Repression of War Crimes, 1944, Article 1.
France’s Penal Code (1992), as amended in 2010, states:
War crimes … consist of offences … committed during an international or non-international armed conflict and in relation to such conflict, and which violate the laws and customs of war or the international conventions applicable to armed conflict. 
France, Penal Code, 1992, as amended in 2010, Article 461-1.
In 1950, during a debate in the Sixth Committee of the UN General Assembly on the Nuremberg Principles established by the International Law Commission, France stated:
The offences listed by the [IMT (Nuremberg)] were based on already existing principles of international law; they were principles “recognized” by the [1945 IMT Charter (Nuremberg)], as was stated in the General Assembly resolution, and not principles “laid down” by that charter.
… The list of war crimes in article 6(b) of the [1945 IMT Charter (Nuremberg)] was based on the definitions of traditional international law contained in the Hague Conventions of 1907, the Treaty of Versailles of 1919 and the Geneva Conventions of 1929. Thus, the concept of war crimes as it was recognized in the [1945 IMT Charter (Nuremberg)] had already existed in 1939. 
France, Statement before the Sixth Committee of the UN General Assembly, UN Doc. A/C.6/ SR.236, 9 November 1950, §§ 9–10.
In a speech before the French National Consultative Commission on Human Rights in 1998, the Director of the Legal Department of the French Ministry of Foreign Affairs noted with regard to the definition of war crimes to be included in the 1998 ICC Statute that the provisions in the “war crimes” section covered what the French referred to as the laws of war, namely the 1949 Geneva Conventions and their 1977 Additional Protocols. He added that it was agreed that in practice the Statute would reflect existing law. 
France, National Consultative Commission on Human Rights, Statement by the Director of the Legal Department of the Ministry of Foreign Affairs, 22 April 1998, p. 3.
In 1998, the French National Consultative Commission on Human Rights recommended:
As regards the definition of war crimes, endorsement must be made [in the 1998 ICC Statute] of the grave breaches of international humanitarian law committed in international as well as in internal armed conflicts, as defined by the Geneva Conventions and their two additional Protocols. 
France, National Consultative Commission on Human Rights, Opinion on the establishment of an international criminal court, 14 May 1998, § 3.
In 1998, at the UN Conference of Plenipotentiaries on the Establishment of an International Criminal Court, the French Minister of Foreign Affairs declared:
Some States are entirely opposed to the idea that the definition of war crimes may apply to internal conflicts. But accepting this restriction would be a retrograde step. Here in Rome we must find a workable solution to this problem. 
France, Minister of Foreign Affairs, Statement at the Diplomatic Conference of Plenipotentiaries on the Establishment of an International Criminal Court, Rome, 17 June 1998.