The Foreign Intelligence Surveillance Act (FISA) is a United States federal law enacted in 1978 that establishes procedures for the surveillance and collection of foreign intelligence on domestic soil. FISA was created in response to revelations of widespread privacy violations by the federal government, particularly during the Nixon administration, and aims to provide judicial and congressional oversight of foreign intelligence surveillance activities while maintaining the secrecy necessary to effectively monitor national security threats.

FISA requires federal law enforcement and intelligence agencies to obtain authorization for gathering "foreign intelligence information" between "foreign powers" and "agents of foreign powers" suspected of espionage or terrorism.
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The law established the Foreign Intelligence Surveillance Court (FISC) to oversee requests for surveillance warrants. Initially, FISA addressed only electronic surveillance, but subsequent amendments have broadened the law to regulate other intelligence-gathering methods, including physical searches, pen register and trap and trace (PR/TT) devices, and compelling the production of certain types of business records.

FISA has been significantly amended over the years, notably by the USA PATRIOT Act following the attacks on September 11, 2001, which expanded surveillance permissions, establishing the ability to surveil US persons.

The Intelligence Reform and Terrorism Prevention Act of 2004 also amended FISA to include a new category of covered individuals called the "lone wolf" provision, which deems a non-United States person who engages in international terrorism or activities in preparation for international terrorism to be an "agent of a foreign power" under FISA ******<----Obama????

FISA prohibits surveillance of or production of business records regarding a U.S. person based solely on First Amendment activities. Despite these protections, FISA has been criticized for potentially violating constitutional rights, particularly the First, Fourth, Fifth, and Sixth Amendments.