Declassification is the process of ceasing a protective classification, often under the principle of freedom of information.
Until 1989 requested information was routinely kept secret invoking the public interest defence; this was largely removed by the 1989 Act.
After 25 years, declassification review is automatic with nine narrow exceptions that allow information to remain as classified.
[2] Because of changes in policy and circumstances, agencies are expected to actively review documents that have been classified for fewer than 25 years.
The National Archives and Records Administration houses the National Declassification Center to coordinate reviews and Information Security Oversight Office to promulgate rules and enforce quality measures across all agencies.