Related Rule
Practice Relating to Rule 107. Spies
Section B. Status of spies
Germany’s Military Manual (1992) states:
Even if they are members of their armed forces, [spies] do not have the right to the status of prisoner of war. Persons who fall into the hands of the adversary while engaging in espionage shall be liable to punishment. Even if taken while engaging in espionage, a spy shall not be punished without prior conviction pursuant to regular judicial proceedings. 
Germany, Humanitarian Law in Armed Conflicts – Manual, DSK VV207320067, edited by The Federal Ministry of Defence of the Federal Republic of Germany, VR II 3, August 1992, English translation of ZDv 15/2, Humanitäres Völkerrecht in bewaffneten KonfliktenHandbuch, August 1992, §§ 321–322.