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Canada
Practice Relating to Rule 75. Riot Control Agents
Canada’s LOAC Manual (1999) states: “The use of riot control agents, including tear gas and other gases that have debilitating but non-permanent effects, as a means of warfare is prohibited.” 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 5-3, § 27.
Canada’s Code of Conduct (2001) provides: “The use of CS gas or pepper spray is lawful and may be used for crowd control purposes, but their use as a means of warfare is illegal.” 
Canada, Code of Conduct for CF Personnel, Office of the Judge Advocate General, 4 June 2001, Rule 3, § 9.
Canada’s LOAC Manual (2001) states in its chapter entitled “Restrictions on the use of weapons”: “The use of riot control agents, including tear gas and other gases that have debilitating but non-permanent effects, as a means of warfare is prohibited.” 
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 518.
Canada’s Code of Conduct (2005) provides: “The use of CS gas or pepper spray is lawful and may be used for crowd control purposes, but their use as a means of warfare is illegal.” 
Canada, Code of Conduct for CF Personnel, Office of the Judge Advocate General, 2005, Rule 3, § 9.
In 1971, during a debate in the UN General Assembly, Canada stated:
Tear gas and other riot- and crowd-control agents were excluded from Canada’s commitment not to develop, produce, acquire, stockpile or use any chemical weapons in warfare … Canada’s reservations with regard to the use of these agents in war should be waived. 
Canada, Statement before the UN General Assembly, UN Doc A/PV.1827, 11 November 1971, p. 7.