Related Rule
Belgium
Practice Relating to Rule 73. Biological Weapons
Belgium’s Law of War Manual (1983) proscribes the use of biological weapons with reference to the 1925 Geneva Gas Protocol and the 1972 Biological Weapons Convention. 
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.
Belgium’s Law Regulating Economic and Individual Activities with Weapons (2006) provides: “[The following] arms shall be considered as prohibited: … devices which are intended to affect people by toxic, asphyxiating … and other similar substances”. 
Belgium, Law Regulating Economic and Individual Activities with Weapons, 2006, Article 3(1)(10).
At the First Review Conference of States Parties to the Biological Weapons Convention in 1980, Belgium stated: “With regard to article IV [of the 1972 Biological Weapons Convention], Belgium, in common with many other States, had taken the necessary domestic measures, the Belgian Parliament having enacted legislation approving the Convention.” 
Belgium, Statement of 7 March 1980 at the First Review Conference of States Parties to the Biological Weapons Convention, Geneva, 3–21 March 1980, UN Doc. BWC/CONF.I/SR.6, 7 March 1980, § 3.