One of the Q posts asked a question about State Secrets Privilege. I had done some research, and this is all I found - it’s not much. The Supreme Court Case 1953 US v Reynolds overruled the lower courts - not one of their better decisions in my opinion.
There has been abuses of power to hide mistakes rather than national security issues. To answer the question, the head of the Agency or Department is required to make a public statement why evidence must not be disclosed.
During the Obama Admin. additional procedure requiring justice to report to oversight committee was implemented.
I thought there might be some interest in this crumb.
Thank you!