PART VI – INTERCEPTION OF COMMUNICATIONS, PRESERVATION OF COMMUNICATIONS DATA AND COVERT ELECTRONIC SURVEILLANCE
31. Preservation of communications data
(5) If the Competent Authority considers that the preservation of communications data pursuant to a request made under this section will not ensure the future availability of the communications data, or will threaten the confidentiality of, or otherwise prejudice the investigation in a requesting state, it shall promptly inform a requesting state, which shall then determine whether the request should nevertheless be executed.
Confidentiality re request for cooperation and supporting documentation
EDIT.