Related Rule
France
Practice Relating to Rule 77. Expanding Bullets
France’s LOAC Summary Note (1992) states: “It is prohibited to use … projectiles that spread or flatten easily in the human body.” 
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, § 4.6.
France’s LOAC Teaching Note (2000) includes dum-dum bullets and other weapons with expanding heads in the list of weapons that “are totally prohibited by the law of armed conflict” because of their inhuman and indiscriminate character. 
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. 6.
France’s LOAC Manual (2001) incorporates the content of the 1899 Hague Declaration concerning Expanding Bullets. 
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. 28.
The manual further includes dum-dum bullets and other weapons with expanding heads in the list of weapons that “are totally prohibited by the law of armed conflict” because of their inhuman and indiscriminate character. 
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. 54.
France’s Penal Code (1992), as amended in 2010, states in its section on war crimes related to international armed conflict: “[The following offences] are punishable by life imprisonment: … [u]sing bullets that easily deform in the human body”. 
France, Penal Code, 1992, as amended in 2010, Article 461-23.