41 C.F.R. § 105-64.209
Law enforcement and security records are generally exempt from disclosure to individuals except when the system manager, in consultation with legal counsel and the Head of the Service or Staff Office or Regional Administrator or their representatives, determines that information in a record has been used or is being used to deny you any right, privilege, or benefit for which you are eligible or entitled under Federal law. If so, the system manager will notify you of the existence of the record and disclose the information, but only to the extent that the information does not identify a confidential source. If disclosure of information could reasonably be expected to identify a confidential source, the record will not be disclosed to you unless it is possible to delete all such information. A confidential source is a person or persons who furnished information during Federal investigations with the understanding that his or her identity would remain confidential.
41 C.F.R. § 105-64.209