Practice Relating to Rule 107. Spies
Spying is not contrary to the law of war and, as a result, does not constitute a war crime. Most countries provide, however, that spying is a crime [under domestic law] in order to protect their national interests and the interests of their armed forces. A person who is caught spying for the enemy is liable to punishment, but only after being tried … In general, civilians act as spies. This activity, by itself, does not give them the status of combatant … Members of the armed forces who perform spying missions in the zone of operations will be treated, if captured, either as prisoners of war or as spies, depending on whether they accomplished their mission wearing their uniform or disguised as civilians wearing civilian clothes.