What can be classified? (see Classified evidence in a court martial):
Firstly, there are no formal requirements concerning how knowledge must be documented in order to constitute information. It must be owned by, produced by or for, or (…) under the control of the United States Government. According to. E.O. 12958, § 1.5. “Classified information falls into seven main subject-matter categories
- Military plans, weapons systems, or operations;
- Foreign government information;
- Intelligence activities (including special activities), intelligence sources or methods, or cryptology;
- Foreign relations or foreign activities of the United States, including confidential sources;
- Scientific, technological, or economic matters relating to the national security;
- United States Government programs for safeguarding nuclear materials or facilities; or
- Vulnerabilities or capabilities of systems, installations, projects or plans relating to the national security.”
The most important element for information to become classified is that the Original Classification Agency (OCA) be able to describe of identify damage to national security that could reasonably be expected by the disclosure of the information.
E.O. 12958, § 1.1(b)