Convention (IV) respecting the Laws and Customs of War on Land
CHAPTER II
Spies
Art. 29. A person can only be considered a spy when, acting clandestinely or on false pretences, he obtains or endeavours to obtain information in the zone of operations of a belligerent, with the intention of communicating it to the hostile party.
Thus, soldiers not wearing a disguise who have penetrated into the zone of operations of the hostile army, for the purpose of obtaining information, are not considered spies. Similarly, the following are not considered spies: Soldiers and civilians, carrying out their mission openly, entrusted with the delivery of despatches intended either for their own army or for the enemy's army. To this class belong likewise persons sent in balloons for the purpose of carrying despatches and, generally, of maintaining communications between the different parts of an army or a territory.
Art. 30. A spy taken in the act shall not be punished without previous trial.
Art. 31. A spy who, after rejoining the army to which he belongs, is subsequently captured by the enemy, is treated as a prisoner of war, and incurs no responsibility for his previous acts of espionage.
(from
http://www.icrc.org/ihl.nsf/full/195)
Article 154 of Convention (IV) relative to the Protection of Civilian Persons in Time of War. Geneva, 12 August 1949 reaffirms these rules and extends them
Article 29 is extended thus:
However, a spy is also a protected person in so far as he conforms to the definition given in Article 4 of the Fourth Convention. Under Article 5 of the Convention, the spy may nevertheless be deprived temporarily of certain rights, particularly the right of communication..
Article 30 is extended thus:The Convention contains several provisions in this respect which extend the principle and make it precise. Thus Article 3 prohibits "the passing of sentences and the carrying out of executions without previous judgement pronounced by a regularly constituted court, affording all the judicial guarantees which are recognized as indispensable by civilized peoples".
Article 3 although it applies only to armed conflicts not of an international character, contains rules of absolutely general application. The prohibition mentioned is, moreover, confirmed by Article 5 and Articles 64-76.
It should also be noted that paragraph 2 of Article 68
authorizes the Occupying Power under certain conditions to inflict the death penalty on protected persons found guilty of espionage.
(from
http://www.icrc.org/ihl.nsf/COM/380-600177?OpenDocument)