Règle correspondante
Practice Relating to Rule 65. Perfidy
Section J. Simulation of protected status by using flags or military emblems, insignia or uniforms of neutral or other States not party to the conflict
Switzerland’s Basic Military Manual (1987) prohibits perfidy. Thus, “it is notably forbidden … to abuse a protected status by using signs, emblems or uniforms … of nations not involved in the conflict”. 
Switzerland, Lois et coutumes de la guerre (Extrait et commentaire), Règlement 51.7/II f, Armée Suisse, 1987, Article 39.
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.