Related Rule
Practice Relating to Rule 68. Precautions while Receiving Parlementaires
Section B. Detention of parlementaires
Germany’s Military Manual (1992) states:
A parlementaire may be temporarily detained if he has accidentally acquired information the disclosure of which to the adversary would jeopardize the success of a current or impending operation of the friendly armed forces. In this case, the parlementaire may be detained until the operation has been completed. 
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, § 228.