When you can talk out of your arse like OP.
Here is what the Electronic Information System for International Law has to say on the matter:
"Espionage may take place both in peacetime and in war although international law is somewhat lacking with regard to espionage in peacetime. With regard to espionage in times of war, espionage is a legitimate operation and does not violate the laws of war."
http://www.eisil.org/index.php?cat=768&t=sub_pages