Related Rule
Canada
Practice Relating to Rule 74. Chemical Weapons
Canada’s LOAC Manual (1999) prohibits the use of asphyxiating, poisonous or other gases “at all times and under all circumstances”. 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 5-3, § 23.
The manual also bans the use of chemical weapons, “which include toxic chemicals and their precursors (those chemicals which can cause death, permanent harm or temporary incapacity to humans or animals) and munitions or devices designed to carry such chemicals”. 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 5-3, § 26.
The manual defines “using asphyxiating, poisonous and other gases” as a war crime. 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, pp. 16-3 and 16-4, § 21(h).
The manual also provides: “Smoke grenades, smoke ammunition from indirect fire weapons and tank smoke ammunition are not prohibited as long as they are used to conceal position or movement or to mask target.” 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 5-3, § 24.
Canada’s Code of Conduct (2001) provides that the use of chemical weapons is forbidden. 
Canada, Code of Conduct for CF Personnel, Office of the Judge Advocate General, 4 June 2001, Rule 3, § 10(d).
Canada’s LOAC Manual (2001) provides in its chapter entitled “Restrictions on the use of weapons”:
The use of asphyxiating, poisonous or other gases is prohibited at all times and under all circumstances … However, smoke grenades, smoke ammunition from indirect fire weapons and tank smoke ammunition are not prohibited so long as they are used to conceal position or movement or to mask a target. 
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 515.
According to the manual, chemical weapons “which include toxic chemicals and their precursors (those chemicals which can cause death, permanent harm or temporary incapacity to humans or animals) and munitions or devices designed to carry such chemicals” are banned. 
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 517.
In its chapter on “War crimes, individual criminal liability and command responsibility”, the manual states that “using asphyxiating, poisonous and other gases” constitutes a war crime. 
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 1609.3.h.
Canada’s Code of Conduct (2005) provides that the use of “chemical weapons” is forbidden. 
Canada, Code of Conduct for CF Personnel, Office of the Judge Advocate General, 2005, Rule 3, § 10(d).
Canada’s Chemical Weapons Act (1995) provides:
No person shall
(a) develop, produce, otherwise acquire, stockpile or retain a chemical weapon or transfer, directly or indirectly, a chemical weapon to anyone;
(b) use a chemical weapon;
(c) engage in any military preparations to use a chemical weapon;
(d) assist, encourage or induce, in any way, anyone to engage in any activity prohibited to a State Party under the Convention. 
Canada, Chemical Weapons Act, 1995, § 6.
Canada’s Crimes against Humanity and War Crimes Act (2000) provides that the war crimes defined in Article 8(2) of the 1998 ICC Statute are “crimes according to customary international law” and, as such, indictable offences under the Act. 
Canada, Crimes against Humanity and War Crimes Act, 2000, Section 4(1) and (4).
In 2013, in the Sapkota case, Canada’s Federal Court dismissed a request for review of a decision denying refugee protection to the applicant on grounds of complicity in crimes against humanity in Nepal between 1991 and 2009. While reviewing the submissions of the respondent, Canada’s Minister of Citizenship and Immigration, the Court stated: “The Respondent notes that the Rome Statute of the International Criminal Court … is endorsed in Canada as a source of customary law.” 
Canada, Federal Court, Sapkota case, Reasons for Judgment and Judgment, 15 July 2013, § 28.
In 1966, during a debate in the First Committee of the UN General Assembly, Canada supported the principle that international law prohibited the use of chemical weapons as a result of the 1925 Geneva Gas Protocol. 
Canada, Statement before the First Committee of the UN General Assembly, UN Doc. A/C.1/ SR.1461, 23 November 1966, p. 203.
At the CDDH, Canada voted against the Philippine amendment (see infra) because “the particular weapons are forbidden by international law and their use, other than by way of reprisal, already constitutes a war crime”. 
Canada, Statement at the CDDH, Official Records, Vol. VI, CDDH/SR.44, 30 May 1977, p. 298.
In 1977, during a debate in the First Committee of the UN General Assembly, Canada, while introducing the draft of UN General Assembly Resolution 32/77, stated that the world community “long ago reached consensus that a high priority should be accorded to early agreement on effective measures for the complete prohibition of the development, production and stockpiling of all chemical weapons and on their destruction”. 
Canada, Statement before the First Committee of the UN General Assembly, UN Doc. A/C.1/ 32/PV.25, 7 October 1977, p. 51.
In 1989, Canada 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”. 
Canada, Draft resolution on the situation of human rights in Iraq, UN Doc. E/CN.4/1989/L.82, 3 March 1989, § 2.
At the First Conference of States Parties to the Chemical Weapons Convention in 1997, Canada emphasized the importance of the 1993 Chemical Weapons Convention and stated its commitment and its determination to contribute actively to the realization of the Convention’s aims. It reconfirmed its good intentions by once more emphasizing its commitment to global chemical disarmament. 
Canada, Statement by the Speaker of the Senate at the First Conference of States Parties to the Chemical Weapons Convention, The Hague, 6–23 May 1997.
In 2013, Canada’s Department of Foreign Affairs, Trade and Development issued a press release entitled “Canadian Leadership in Addressing Syrian Crisis”, which stated: “Foreign Affairs Minister John Baird today announced that Canada is providing real leadership to help address the effects of raging crisis in Syria. … ‘We continue to warn the Syrian regime, and all parties to the Syrian conflict, against any use of chemical agents.’” 
Canada, Department of Foreign Affairs, Trade and Development, “Canadian Leadership in Addressing Syrian Crisis”, Press Release, 7 April 2013.
In 2013, Canada’s Department of Foreign Affairs, Trade and Development issued a press release entitled “[Foreign Affairs Minister] Baird Concerned by Reports of Syrian Gas Attack”, which stated:
Foreign Affairs Minister John Baird today issued the following statement:
Canada is concerned by reports of a poison gas attack near Syria’s capital of Damascus that left hundreds of people dead, including children.
Such reports are extremely concerning, and we will continue to monitor the situation closely with our allies and to seek further information.
Such an attack is completely unacceptable.  
Canada, Department of Foreign Affairs, Trade and Development, “[Foreign Affairs Minister] Baird Concerned by Reports of Syrian Gas Attack”, Press Release, 21 August 2013.
In 2013, Canada’s Office of the Prime Minister issued a press release entitled “Prime Minister Harper speaks with President Obama”, which stated:
The Prime Minister made it clear that he shares the view that the recent chemical weapons attack was carried out by the Syrian regime and described the use of these weapons as an outrage. … Both leaders agreed that significant use of chemical weapons merits a firm response from the international community in an effective and timely manner. 
Canada, Office of the Prime Minister, “Prime Minister Harper speaks with President Obama”, Press Release, 27 August 2013.
In 2013, Canada’s Department of Foreign Affairs, Trade and Development issued a press release entitled “[Foreign Affairs Minister] Baird Comments on UN Chemical Weapons Report”, which stated:
Foreign Affairs Minister John Baird today issued the following statement:
The report submitted by UN inspectors today confirmed to the world the despicable way in which chemical weapons were used against innocent Syrians on August 21, 2013.
This report provides additional evidence supporting the conclusion that inhumane and indiscriminate chemical weapons were used by the … regime. 
Canada, Department of Foreign Affairs, Trade and Development, “[Foreign Affairs Minister] Baird Comments on UN Chemical Weapons Report”, Press Release, 16 September 2013.
In 2013, during a meeting of the Friends of the Syrian People, Canada’s Minister of Foreign Affairs stated:
The report submitted by UN inspectors confirmed to the world the use of chemical weapons on August 21, 2013, and provided additional evidence supporting the conclusion that the … regime was responsible for the use of these inhumane and indiscriminate weapons. The international community must unite in strongly condemning the use of chemical weapons and taking action to deter any future use. 
Canada, Remarks by the Minister of Foreign Affairs at the meeting of the Friends of the Syrian People, 26 September 2013.
In 2013, in a statement during the 68th Session of the UN General Assembly, the Minister of Foreign Affairs of Canada stated:
Canada joins the entire world in seeking a political resolution to the conflict. Canada supports a peaceful, democratic and pluralistic Syria that protects the rights of all communities.
But let us not confuse a peaceful, negotiated outcome with equivocation or moral uncertainty. There can be no moral ambiguity about the use of chemical weapons on civilians. 
Canada, Address by the Minister of Foreign Affairs during the 68th Session of the UN General Assembly, 30 September 2013.