Related Rule
Belgium
Practice Relating to Rule 74. Chemical Weapons
Belgium’s Law of War Manual (1983), with reference to the 1925 Geneva Gas Protocol, proscribes “the use of asphyxiating, toxic or similar gases, as well as all liquids, materials or analogous devices”, with a reservation on the first use. 
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 Penal Code (1867), as amended in 2003, provides:
War crimes envisaged in the 1949 [Geneva] Conventions … and in the [1977 Additional Protocols I and II] … , as well as in Article 8(2)(f) of the [1998 ICC Statute], and listed below, … constitute crimes under international law and shall be punished in accordance with the provisions of the present title … :
37. employing asphyxiating, poisonous or other gases, and all analogous liquids, materials or devices. 
Belgium, Penal Code, 1867, as amended on 5 August 2003, Chapter III, Title I bis, Article 136 quater, § 1(37).
Belgium’s Law relating to the Repression of Grave Breaches of International Humanitarian Law (1993), as amended in 2003, provides:
War crimes envisaged in the 1949 [Geneva] Conventions … and in the [1977 Additional Protocols I and II] … , as well as in Article 8(2)(f) of the [1998 ICC Statute], and listed below, … constitute crimes under international law and shall be punished in accordance with the provisions of the present title … :
23. employing asphyxiating, poisonous or other gases, and all analogous liquids, materials or devices. 
Belgium, Law relating to the Repression of Grave Breaches of International Humanitarian Law, 1993, as amended on 23 April 2003, Article 1 ter, § 1(23).
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 means of toxic, asphyxiating … and other similar substances”. 
Belgium, Law Regulating Economic and Individual Activities with Weapons, 2006, Article 3(1)(10).
In 1980, in a statement before the Lower House of Parliament, Belgium’s Minister of Foreign Affairs stated that disapproval of the hostile use of chemical agents in combat, as well as the 1925 Geneva Gas Protocol, was part of customary law. 
Belgium, Lower House of Parliament, Statement by the Minister of Foreign Affairs, Bulletin des Questions et Réponses, 1979–1980 Session, No. 36, 8 August 1980.
In 1987, during a debate in the First Committee of the UN General Assembly, Belgium stated that the use of chemical weapons in the Iran–Iraq War against civilian populations was a “particularly shocking violation of the 1925 Geneva [Gas] Protocol”. 
Belgium, Statement before the First Committee of the UN General Assembly, UN Doc. A/C.1/ 42/PV.6, 15 October 1987, p. 42.
In 1989, Belgium co-sponsored a draft resolution in the UN Commission on Human Rights which expressed “grave concern about reports of killing of unarmed Kurdish civilians, in particular by military attacks during 1988 using, inter alia, chemical weapons and causing mass exodus to neighbouring countries”. 
Belgium, Draft resolution on the situation of human rights in Iraq, UN Doc. E/CN.4/1989/L.82, 3 March 1989, § 2.
At the 1989 Session of the Government-Industry Conference against Chemical Weapons, Belgium stated that it
attaches the greatest importance to the unanimous expression of a willingness to respect the Geneva Gas Protocol on the part of all participants. As we are moving towards a treaty which totally prohibits chemical weapons we all have to contribute to the realization of this goal, the finalization of the draft treaty, universal adherence and confidence in its being respected.
Belgium added:
Belgium has no chemical weapons and has no intention to acquire any. It is taking the necessary steps to eliminate, in optimal conditions, the chemical bombs dating from the First World War which are periodically found on its soil. 
Belgium, Statement at the Government-Industry Conference against Chemical Weapons, Canberra, 12–22 September 1989, Final Record, p. 280, §§ 6 and 8.