Related Rule
Colombia
Practice Relating to Rule 74. Chemical Weapons
Colombia’s Basic Military Manual (1995) states that the use of weapons which “cause unnecessary and indiscriminate, extensive, lasting and serious damage to people and the environment” is prohibited. It adds that the use of chemical weapons, as well as their production, possession and importation, is banned. 
Colombia, Basic Derecho Internacional Humanitario – Manual Básico para las Personerías y las Fuerzas Armadas de Colombia, Ministerio de Defensa Nacional, 1995, pp. 49–50.
Colombia’s Constitution (1991) prohibits “the manufacture, import, possession, and use of chemical … weapons”. 
Colombia, Constitution, 1991, Article 81.
Colombia’s Decree on the Control of Firearms, Ammunition and Explosives (1993) provides: “It is prohibited to carry devices manufactured on the basis of poisoned gases, corrosive substances or metal which by the expansion of gas produces fragments.” 
Colombia, Decree on the Control of Firearms, Ammunition and Explosives, 1993, Article 14.
In 1995, in a ruling on the constitutionality of the 1977 Additional Protocol II, Colombia’s Constitutional Court stated in relation to the prohibition on the use of weapons of a nature to cause unnecessary suffering or superfluous injury:
Although none of the treaty rules expressly applicable to internal conflicts prohibits indiscriminate attacks or the use of certain weapons, the Taormina Declaration consequently considers that the bans (established partly by customary law and partly by treaty law) on the use of chemical … weapons … apply to non-international armed conflicts, not only because they form part of customary international law but also because they evidently derive from the general rule prohibiting attacks against the civilian population. 
Colombia, Constitutional Court, Constitutional Case No. C-225/95, Judgment, 18 May 1995, § 23.
In 1977, during a debate in the First Committee of the UN General Assembly, Colombia supported a complete ban on chemical weapons. 
Colombia, Statement before the First Committee of the UN General Assembly, UN Doc. A/C.1/32/PV.21, 5 October 1977, p. 11.
At the 1981 Session of the Government-Industry Conference against Chemical Weapons, Colombia stated:
The Colombian Government, as it represents a country which does not manufacture or possess, nor intends to manufacture or possess, chemical weapons, as well as other weapons of mass destruction, cannot but condemn the production, the possession, transfer and the use of such weapons. 
Colombia, Final Statement at the Government-Industry Conference against Chemical Weapons, GICCW/P/72 (Prov), Canberra, 21 September 1981, pp. 1–3.
In 1989, in reply to a note verbale of the UN Secretary-General on the subject of chemical weapons, Colombia declared that it did not possess chemical weapons. 
Colombia, Reply to a note verbale of the UN Secretary-General, referred to in Report of the Secretary-General on respect for the right to life: elimination of chemical weapons, prepared in accordance with UN Sub-Commission on Human Rights Resolution 1988/27, UN Doc. E/CN.4/Sub.2/1989/4, 17 August 1989, § 98.