A newly revised Pentagon instruction (pdf) updates Freedom of Information Act policy regarding requests submitted to the Office of the Secretary of Defense and the Joint Chiefs of Staff.
“A classified document containing unclassified information may not be denied in total under exemption 1 [of the Freedom of Information Act, which exempts properly classified information] unless the unclassified information, when taken in aggregate, would reveal classified information.”
Furthermore, the instruction says, “It is OSD policy that OSD and JS Components shall promote the public trust by making the maximum amount of information available to the public on the operation and activities of the Department of Defense, consistent with the Department’s responsibility to ensure national security.”
See Office of the Secretary of Defense and Joint Staff (JS) Freedom of Information Act (FOIA) Program, Administrative Instruction No. 108, September 29, 2008.