Abstract The state secrets privilege is the most formidable evidentiary privilege available to the United States government. Available only to the executive branch, it is used to protect national security information from disclosure during litigation, and is habitually acquiesced to by courts. Once invoked, the privilege prevents covered material from being put into evidence that touches sensitive matters of national security. It is apparent that this privilege is subject to abuse by the executive branch to shield activities and personnel from judicial scrutiny and legal inquiries for reasons other than to protect national security. The privilege derives from British and Scottish doctrines of Crown Privilege that allow government to withhold evidence from legal proceedings to protect the public interest. The derivation of the state secrets privilege from the tradition of Crown Privilege has never been thoroughly explored. This article traces the influence of Crown Privilege in the development and evolution of the state secrets doctrine in the United States.