5 U.S.C. § 552(b)(1), Classified national defense and foreign relations information
What that means: Classified national defense and foreign relations information. Spy and/or military stuff, mostly.
What you can do about it: Depends on how recent the docs are. If it’s anywhere near the vicinity of this decade, you’re probably out of luck. If it’s on the older side, you might have a case for a Mandatory Declassification Review.
Any other resources? The consistently excellent folks over at National Security Archive have a great guide on how and when to file an MDR - there’s even a flowchart! Speaking of the NSA(rchive), Friend of MuckRock Nate Jones has an entire book on his decade plus efforts to get records declassified that comes highly recommended. Also, check out our interview with Jason Leopold, which has some solid pointers on MDRs.
Material that is over 25 years old, and therefore no longer properly classified under Executive Order 12958
This information is over 25 years old, I hereby request a Mandatory Declassification Review, as this material no longer meets the standards for classification.
Information whose release would reasonably pose a threat to national security
Material properly classified to such Executive Order #12958
Material over 25 years old, after which point it should have been automatically declassified
Material not explicitly classified by Executive Order