Whenever an agency is processing a request pursuant to section 552 of title 5 (commonly known as the “Freedom of Information Act”) or the mandatory declassification review provisions of Executive Order 13526 (50 U.S.C. 3161 note; relating to classified national security information), or successor order, and identifies responsive classified records that are more than 25 years of age as of December 31 of the year in which the request is received, the head of the agency shall, in accordance with existing processes to protect national security under the Freedom of Information Act and the mandatory review provisions of Executive Order 12526,1 review the record and process the record for declassification and release by the National Declassification Center of the National Archives and Records Administration, unless the head of agency—