Related Rule
Belgium
Practice Relating to Rule 85. The Use of Incendiary Weapons against Combatants
Belgium’s Law Regulating Economic and Individual Activities with Weapons (2006) provides:
For the purposes of the present law and its implementing decrees, an “incendiary weapon” is considered as … any weapon or munition which is primarily designed to set fire to objects or to cause burn injury to persons through the action of flame, heat, or a combination thereof, produced by a chemical reaction of a substance delivered on the target. 
Belgium, Law Regulating Economic and Individual Activities with Weapons, 2006, Article 2(6).
The Law further states: “[The following] arms shall be considered as prohibited: … incendiary weapons”. 
Belgium, Law Regulating Economic and Individual Activities with Weapons, 2006, Article 3(1)(2).
In 1972, during a debate preceding the adoption of Resolution 3032 (XXVII) in which the UN General Assembly called upon “all parties to armed conflicts to observe the international humanitarian rules which are applicable, in particular the Hague Conventions of 1899 and 1907”, Belgium stated that this paragraph contained a very clear reference to napalm. 
Belgium, Statement before the Sixth Committee of the UN General Assembly, UN Doc. A/C.6/SR.1388, 9 December 1972, p. 468.
Belgium’s Law of War Manual (1983) states: “The use of [incendiary] weapons against persons is prohibited because they cause unnecessary suffering, but their use against military objectives, such as bunkers, tanks, depots, etc. is permitted.” 
Belgium, Droit Pénal et Disciplinaire Militaire et Droit de la Guerre, Deuxième Partie, Droit de la Guerre, Ecole Royale Militaire, par J. Maes, Chargé de cours, Avocat-général près la Cour Militaire, D/1983/1187/029, 1983, p. 38.