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Switzerland
Practice Relating to Rule 62. Improper Use of Flags or Military Emblems, Insignia or Uniforms of the Adversary
Switzerland’s Basic Military Manual (1987) provides: “It is notably forbidden … to abuse a protected status by using … emblems or uniforms of the adverse nation.” It regards this behaviour as a perfidious act. 
Switzerland, Lois et coutumes de la guerre (Extrait et commentaire), Règlement 51.7/II f, Armée Suisse, 1987, Article 39.
The manual further stresses: “It is prohibited to use improperly the military insignia or uniform of the enemy.” It gives the example of the prohibition of attacking the enemy while wearing its uniform. 
Switzerland, Lois et coutumes de la guerre (Extrait et commentaire), Règlement 51.7/II f, Armée Suisse, 1987, Article 40, including commentary.
Switzerland’s Regulation on Legal Bases for Conduct during an Engagement (2005) states:
15.2 Prohibited methods of warfare
224 Wearing enemy uniforms or feigning protected status by using the insignia, emblems or uniforms of the United Nations or of neutral States or States that are not party to the conflict is 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, § 224.
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. 112c
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:
g. makes improper use … of the flag, the uniform, the military insignia of the enemy[.] 
Switzerland, Military Criminal Code, 1927, taking into account amendments entered into force up to 2011, Articles 110 and 112c (1)(g).
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. 264g
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:
g. makes improper use … of the flag, the uniform, the military insignia of the enemy[.] 
Switzerland, Penal Code, 1937, taking into account amendments entered into force up to 2011, Articles 264b and 264g (1)(g).