Related Rule
Switzerland
Practice Relating to Rule 107. Spies
Section A. Definition of spies
Switzerland’s Basic Military Manual (1987) defines a spy as “an individual who, acting clandestinely or on false pretences, gathers or attempts to gather information in the zone of operation of a belligerent with the intention of communicating it to the adverse party”. 
Switzerland, Lois et coutumes de la guerre (Extrait et commentaire), Règlement 51.7/II f, Armée Suisse, 1987, Article 42.
Switzerland’s Regulation on Legal Bases for Conduct during an Engagement (2005) states:
220 Gathering information and conducting reconnaissance are permissible at any time. If, when gathering information while in uniform, combatants fall into the hands of the enemy, they must be treated as prisoners of war.
221 Gathering information in a clandestine manner or under a false pretext (e.g. in civilian attire or enemy uniform) is considered espionage. Spies are subject to the criminal law of the State that arrests them (in Switzerland: the Military Criminal Code) and face severe penalties after their arrest. They are not entitled to prisoner-of-war status.
222 Acts of sabotage (i.e. harmful acts committed behind enemy lines) are permitted, as long as they are carried out by combatants in uniform and are aimed exclusively at military objectives. If captured, combatants who have committed acts of sabotage are entitled to prisoner-of-war status. 
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, §§ 220–222.
Switzerland’s Military Criminal Code (1927), as amended in 2007, states:
A person who has gathered military information on Swiss territory for a foreign State to the detriment of another foreign State or has organized such service … shall be liable to a custodial sentence not exceeding three years or to a monetary penalty. 
Switzerland, Military Criminal Code, 1927, as amended in 2007, Article 93(1).
Switzerland’s Military Criminal Code (1927), taking into account amendments entered into force up to 2011, states:
Art. 93
1 A person who, on Swiss territory, has gathered military information for a foreign State to the detriment of another foreign State or has organized such a service,
anyone who has recruited someone else for such a service or has encouraged such acts,
shall be liable to a custodial sentence not exceeding three years or to a monetary penalty. 
Switzerland, Military Criminal Code, 1927, taking into account amendments entered into force up to 2011, Article 93(1).
Switzerland’s Penal Code (1937), taking into account amendments entered into force up to 2011, which also contains a title on war crimes, states under the title “Felonies or misdemeanours against the State or national defence”:
Art. 274
1 A person who has gathered military information in the interest of a foreign State and to the detriment of Switzerland or has organized such a service,
anyone who has recruited someone else for such a service or has encouraged such acts,
shall be liable to a custodial sentence not exceeding three years or to a monetary penalty. 
Switzerland, Penal Code, 1937, taking into account amendments entered into force up to 2011, Article 274(1). See also Articles 4(1), 267(1) and 272(1).
Switzerland’s ABC of International Humanitarian Law (2009) states:
Spies
A spy is a person who secretly attempts to obtain information of military importance in enemy controlled territory. Spies operating in civilian clothes are not entitled to the status of Combatants and if captured are not accorded the status of Prisoners of war. Spies in uniform on the other hand do count as combatants and are to be accorded prisoner of war status if captured. 
Switzerland, Federal Department of Foreign Affairs, ABC of International Humanitarian Law, 2009, p. 38.