In CIA v. Sims, the United States Supreme Court held that the CIA could withhold information about controversial government-sponsored psychological experiments in response to Freedom of Information Act (FOIA) requests. The Court reasoned that the requested information would reveal intelligence sources related to national defense, which were specifically protected from disclosure under the National Security Act of 1947. Accordingly, the Court concluded that the CIA could refuse to disclose the information under FOIA Exemption 3, which allows withholding of information “specifically exempted from disclosure by statute.” Numerous scholars assailed Sims, arguing that the Court's broad reading of the National Security Act gave the CIA carte blanche to withhold information and operate with no accountability. Sims' implications, however, go far beyond giving the CIA the ability to conceal its activities from scrutiny. Sims relied, in part, on a controversial theory known as mosaic theory--the notion that the government may withhold otherwise trivial or innocuous information because it might prove dangerous if combined with other information by a knowledgeable actor (especially a hostile intelligence agency). Reliance on mosaic theory expands the universe of exempt information and often leads to non-disclosure of information that otherwise would have been disclosed. The core of mosaic theory--that hostile intelligence agencies can piece together puzzles from smaller bits of information--can be a legitimate one.
Christina E. Wells, Cia v. Sims: Mosaic Theory and Government Attitude, 58 Admin. L. Rev. 845 (2006)