The Foreign Intelligence Surveillance Act of 1978 (FISA, Pub. L. 95–511, 92 Stat. 1783, 50 U.S.C. ch. 36) is a United States federal law that establishes procedures for the surveillance and collection of foreign intelligence on domestic soil. FISA was enacted in response to revelations of widespread privacy violations by the federal government under president Richard Nixon.
https://en.wikipedia.org/wiki/Foreign_Intelligence_Surveillance_Act