Related Rule
Canada
Practice Relating to Rule 68. Precautions while Receiving Parlementaires
Section B. Detention of parlementaires
Canada’s LOAC Manual (1999) provides:
If the parlementaire remains within enemy lines after being ordered to withdraw, he loses his inviolability and may be made a PW [prisoner of war]. Detention may occur if the parlementaire has abused the position of parlementaire, for example, by collecting information covertly. It is not an abuse of the position for the parlementaire, however, to report on observations made. 
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 14-1, § 9.
Canada’s LOAC Manual (2001) states in its chapter entitled “Communications and contact between opposing forces”:
7. After making contact with the adverse party, the parlementaire must obey any orders that a party provides regarding the entry of that party’s lines, and must withdraw if so instructed. During the withdrawal and return to the parlementaire’s own lines, the parlementaire continues to enjoy inviolability and may not be attacked. When ordered to withdraw, the parlementaire must be given a reasonable time in which to do so. Failure to withdraw results in loss of protection and the parlementaire may then be fired upon. If the parlementaire remains within enemy lines after being ordered to withdraw, he loses his inviolability and may be made a PW [prisoner of war]. Detention may occur if the parlementaire has abused the position of parlementaire, for example, by collecting information covertly. It is not an abuse of the position for the parlementaire, however, to report on observations made.
9. … Any measure that may be taken against the parlementaire or attending members of the party must be reported to the sending belligerent without delay. 
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 1402.7 and 9.