Related Rule
Switzerland
Practice Relating to Rule 65. Perfidy
Section G. Simulation of protected status by using the United Nations emblem or uniform
Switzerland’s Basic Military Manual (1987) considers the “perfidious use of … distinctive signs recognized by the [1949 Geneva] Conventions or [the 1977 Additional Protocol I], in violation of Article 37 [of the 1977 Additional Protocol I]”, as a grave breach of the 1977 Additional Protocol I. 
Switzerland, Lois et coutumes de la guerre (Extrait et commentaire), Règlement 51.7/II f, Armée Suisse, 1987, Article 193(1)(f).
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 ABC of International Humanitarian Law (2009) states:
Perfidy
International humanitarian law prohibits killing, injuring or capturing an adversary by resorting to perfidy. Acts of perfidy include any form of deception designed to win the confidence of an adversary and lead him to believe that he is entitled or obliged to accord protection under the rules of international humanitarian law, with the intention of betraying that confidence. An example of perfidy is to falsely lay claim to protected status through the misuse of signs or emblems[.] 
Switzerland, Federal Department of Foreign Affairs, ABC of International Humanitarian Law, 2009, p. 34.
In 2010, in its Report on IHL and Current Armed Conflicts, Switzerland’s Federal Council stated:
3.3 Increasing use of guerrilla tactics…
International humanitarian law in force treats these cases in a relatively complete manner, binding non-State and State actors alike. Feigning to have protected civilian status or another protected status (e.g. … member of the UN) in order to kill, injure or capture an adversary constitutes an act of perfidy contrary to international law. 
Switzerland, Federal Council, Report on IHL and Current Armed Conflicts, 17 September 2010, Section 3.3, p. 12.
[footnotes in original omitted]