32 C.F.R. § 2001.15
(b) General content of classification guides. Classification guides shall, at a minimum:
(9) Prescribe a specific date or event for declassification, the marking “50X1-HUM” or “50X2-WMD” as appropriate, or one or more of the exemption codes listed in 2001.26(a)(2), provided that:
(d) Reviewing and updating classification guides.