32 C.F.R. § 2400.15 – Classification guides.

(a) OSTP shall issue and maintain classification guides to facilitate the proper and uniform derivative classification of information. These guides shall be used to direct derivative classification.
(b) The classification guides shall be approved, in writing, by the Director or by officials having Top Secret original classification authority. Such approval constitutes an original classification decision.
(c) Each classification guide shall specify the information subject to classification in sufficient detail to permit its ready and uniform identification and categorization and shall set forth the classification level and duration in each instance. Additionally, each classification guide shall prescribe declassification instructions for each element of information in terms of (1) a period of time, (2) the occurrence of an event, or (3) a notation that the information shall not be automatically declassified without the approval of OSTP.
(d) The classification guides shall be kept current and shall be fully reviewed at least every two years. The Executive Director, OSTP shall maintain a list of all OSTP classification guides in current use.
(e) The Executive Director, OSTP shall receive and maintain the record copy of all approved classification guides and changes thereto. He will assist the originator in determining the required distribution.
(f) The Director may, for good cause, grant and revoke waivers of the requirement to prepare classification guides for specified classes of documents or information. The Director of the Information Security Oversight Office shall be notified of any waivers. The Director's decision to waive the requirement to issue classification guides for specific classes of documents or information will be based, at a minimum, on an evaluation of the following factors:
1. (1) The ability to segregate and describe the elements of information;
2. (2) The practicality of producing or disseminating the guide because of the nature of the information;
3. (3) The anticipated usage of the guide as a basis for derivative classification; and
4. (4) The availability of alternative sources for derivatively classifying the information in a uniform manner.