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Switzerland
Practice Relating to Rule 73. Biological Weapons
Switzerland’s Teaching Manual (1986) states that the use of bacteriological means of warfare is prohibited. 
Switzerland, Droit des gens en temps de guerre, Programme d’instruction fondé sur le Manuel 51.7/III “Lois et coutumes de la guerre”, Cours de base pour recrues de toutes les armes 97.2f, Armée suisse, 1986, p. 41.
Switzerland’s Basic Military Manual (1987) prohibits the use of biological weapons. 
Switzerland, Lois et coutumes de la guerre (Extrait et commentaire), Règlement 51.7/II f, Armée Suisse, 1987, Article 22.
Switzerland’s Regulation on Legal Bases for Conduct during an Engagement (2005) states:
16.1 Prohibited means of warfare
228 Prohibited are:
1 poison, chemical and biological weapons;
229 The production, stockpiling, import, export, transit and use of such means of combat are notably prohibited. 
Switzerland, Bases légales du comportement à l’engagement (BCE), Règlement 51.007/IVf, Swiss Army, issued based on Article 10 of the Ordinance on the Organization of the Federal Department for Defence, Civil Protection and Sports of 7 March 2003, entry into force on 1 July 2005, §§ 228–229.
Switzerland’s Military Criminal Code (1927), as amended, punishes “whoever will intentionally spread a dangerous and transmissible human disease”. 
Switzerland, Military Criminal Code, 1927, as amended, Article 167.
Switzerland’s Military Criminal Code (1927), taking into account amendments entered into force up to 2011, states in a chapter entitled “War crimes”:
Art. 110
Articles 112–114 apply in the context of international armed conflicts, including in situations of occupation, and, if the nature of the offence does not exclude it, in the context of non-international armed conflicts.
Art. 112d
1 The penalty shall be a custodial sentence of not less than three years for any person who, in the context of an armed conflict:
b. employs biological or chemical weapons, including poisonous or asphyxiating gases, substances or liquids. 
Switzerland, Military Criminal Code, 1927, taking into account amendments entered into force up to 2011, Articles 110 and 112d (1)(b).
Switzerland’s Penal Code (1937), taking into account amendments entered into force up to 2011, states under the title “War crimes”:
Art. 264b
Articles 264d–264j apply in the context of international armed conflicts, including in situations of occupation, and, if the nature of the offence does not exclude it, in the context of non-international armed conflicts.
Art. 264h
1 The penalty shall be a custodial sentence of not less than three years for any person who, in the context of an armed conflict:
b. employs biological or chemical weapons, including poisonous or asphyxiating gases, substances or liquids. 
Switzerland, Penal Code, 1937, taking into account amendments entered into force up to 2011, Articles 264b and 264h (1)(b).
Switzerland’s Federal Law on War Equipment (1996), as amended in 2001, provides:
It is prohibited:
a.to develop, produce, deliver to anyone, acquire, import, export, procure the transit of or stockpile biological weapons, engage in the brokerage thereof or otherwise dispose of them;
b.to induce anyone to commit an act mentioned under letter a;
c.to facilitate the commission of an act mentioned under letter a. 
Switzerland, Federal Law on War Equipment, 1996, as amended in 2001, Article 7.
At the CDDH, Switzerland voted in favour of the Philippine amendment (see supra) because:
It would be a step forward to state expressly that any violation of The Hague Declaration of 1899 and the Geneva Protocol of 1925 would constitute a grave breach. The rules laid down in those two instruments were undisputed and indisputable, and the amendment would have a deterrent effect on any State tempted to violate them, by exposing the members of its armed forces to the penalties applicable under the Geneva Conventions. 
Switzerland, Statement at the CDDH, Official Records, Vol. VI, CDDH/SR.44, 30 May 1977, p. 281, § 9.
At the First Review Conference of States Parties to the Biological Weapons Convention in 1980, Switzerland stated:
Since it had possessed no bacteriological or toxin weapons before the conclusion of the [1972 Biological Weapons Convention], Switzerland had had no stocks to destroy. With regard to the other States parties, he regretted that they had not all given formal assurances on that point. The Swiss army actually had a biological branch, but its sole purpose was to care for the health of army personnel; it would play only a protective role if bacteriological weapons were used against Switzerland in an armed conflict. 
Switzerland, 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, § 7.
At the Fourth Review Conference of States Parties to the Biological Weapons Convention in 1996, Switzerland stated that it had never equipped itself with biological weapons and that its research in this field was strictly limited to protective measures. It further stated that since 30 June 1972, it had enacted a law which subjects the production, importation and exportation of all weaponry to authorization. 
Switzerland, Statement of 25 November 1996 at the Fourth Review Conference of States Parties to the Biological Weapons Convention, Geneva, 25 November–6 December 1996.
In 2005, in a report in response to a parliamentary postulate on private security and military companies, Switzerland’s Federal Council stated: “International humanitarian law also limits the conduct of military operations permissible under international law. … The use of certain weapons such as biological or chemical weapons is also forbidden.” 
Switzerland, Report by the Swiss Federal Council on Private Security and Military Companies, 2 December 2005, Section 5.3.1, pp. 45–46.
Switzerland’s ABC of International Humanitarian Law (2009) states:
Biological weapons
Biological Weapons are also known as bacteriological weapons. These are designed to cause disease and death. Biological weapons contain living organisms that reproduce and release toxins dangerous to humans, animals and plants. As well as endangering health they cause damage to the environment. The use of biological weapons has been prohibited since 1925. The Biological Weapons Convention of 1972 prohibits the development, production or stockpiling of weapons that contain microbiological and bacteriological agents and toxins, as well as their means of delivery. It also recommends the destruction of such weapons.
Weapons
International humanitarian law imposes limitations, in some cases a total ban, on the use of weapons whose impact goes beyond the permissible purpose of weakening the enemy. Weapons are prohibited on the basis of three fundamental criteria: if their use inevitably leads to death; if they cause disproportionate injury or Unnecessary suffering; if they strike indiscriminately. On the basis of these three criteria a number of specific weapons have been explicitly prohibited by international conventions, including … Biological and Chemical weapons. Some of these bans are part of Customary international law. …
Weapons of mass destruction
The definition of weapons of mass destruction includes Nuclear weapons as well as Biological and Chemical weapons. They differ from other Weapons in their capability to injure and kill people and destroy property on a massive scale, as well as to cause extensive and lasting damage to the environment. 
Switzerland, Federal Department of Foreign Affairs, ABC of International Humanitarian Law, 2009, pp. 9, 40 and 41.
In 2009, in its Report on Foreign Policy, Switzerland’s Federal Council stated:
Switzerland’s second priority focuses on the total elimination of all weapons of mass destruction and the prevention of their dissemination … The absence of progress, in particular on nuclear and biological weapons more and more erodes the value of the instruments concerning them. 
Switzerland, Federal Council, Report on Foreign Policy 2009, 2 September 2009, Section 3.3.5.2, p. 5786.
[emphasis in original]
In 2010, in its Report on Foreign Policy, Switzerland’s Federal Council stated:
Nationally, Switzerland endeavours to apply the BTWC [1972 Biological Weapons Convention] to the best of its abilities. In 2009, the first series of demonstrations took place in universities and research institutes in order to raise awareness of the Swiss research community on the problems of dual use in biotechnological research. The next scheduled step is institutionalizing these activities to fulfil a commitment established by the BTWC, namely the prevention of the proliferation of biological materials. 
Switzerland, Federal Council, Report on Foreign Policy 2010, 10 December 2010, Section 4.5.2, pp. 1139–1140.
[emphasis in original]
In 2012, in the report on Switzerland’s arms control and disarmament policy, Switzerland’s Federal Council stated: “Switzerland is in favour of the prohibition of all types of weapons of mass destruction, as these pose heavy threats against international security as well as against populations”. 
Switzerland, Report of the Federal Council on Switzerland’s arms control and disarmament policy, 30 November 2012, p. 10.
In 2013, in a statement at the Fourth Meeting of States Parties to the Convention on Cluster Munitions, the ambassador of Switzerland stated: “[C]luster munitions have been now classified in Swiss law in the category of prohibited arms, which already include nuclear, biological and chemical weapons as well as anti-personnel mines.” 
Switzerland, Statement by the ambassador of Switzerland at the Fourth Meeting of States Parties to the Convention on Cluster Munitions, 10 September 2013.