The Invention Secrecy Act of 1951, codified at 35 U.S.C. [en.wikipedia.org]  § 181 [www.law.cornell.edu]– 188 [www.law.cornell.edu] (Title 35, Chapter 17 of the United States Code [en.wikipedia.org]), is a body of United States federal law [en.wikipedia.org] designed to prevent disclosure of new inventions [en.wikipedia.org] and technologies [en.wikipedia.org] that, in the opinion of selected federal agencies [en.wikipedia.org], present a possible threat to the national security [en.wikipedia.org] of the United States.

The U.S. government [en.wikipedia.org] has long sought to control the release of new technologies that might threaten the national defense [en.wikipedia.org] and economic stability of the country. During World War I [en.wikipedia.org], Congress [en.wikipedia.org] authorized the United States Patent and Trademark Office [en.wikipedia.org] (PTO) to classify certain defense-related patents [en.wikipedia.org]. This initial effort lasted only for the duration of that war but was reimposed in October 1941 [en.wikipedia.org] in anticipation of the U.S. entry into World War II [en.wikipedia.org]. Patent secrecy orders were initially intended to remain effective for two years, beginning on July 1, 1940, but were later extended for the duration of the war.

The Invention Secrecy Act of 1951 made such patent secrecy permanent. Under this Act, defense agencies [en.wikipedia.org] provide the PTO with a classified list of sensitive technologies in the form of the "Patent Security Category Review List" (PSCRL). The decision to classify new inventions under this act is made by "defense agencies" as defined by the President [en.wikipedia.org]. Generally, these agencies include the Army [en.wikipedia.org], Navy [en.wikipedia.org], Air Force [en.wikipedia.org], National Security Agency [en.wikipedia.org] (NSA), Department of Energy [en.wikipedia.org], and NASA [en.wikipedia.org], but even the Justice Department [en.wikipedia.org] has played this role."