The Foreign Intelligence Surveillance Act of 1978

Like Title III of the Omnibus Crime Control and Safe Streets Act of 1968 (the "Wiretap Act"), the FISA legislation was the result of congressional investigations into Federal surveillance activities conducted in the name of national security. Through FISA, Congress sought to provide judicial and congressional oversight of foreign intelligence surveillance activities while maintaining the secrecy necessary to effectively monitor national security threats. FISA was initially enacted in 1978 and sets out procedures for physical and electronic surveillance and collection of foreign intelligence information. Initially, FISA addressed only electronic surveillance but has been significantly amended to address the use of pen registers and trap and trace devices, physical searches, and business records.
FISA also established the United States Foreign Intelligence Surveillance Court (FISC), a special U.S. Federal court that holds nonpublic sessions to consider issuing search warrants under FISA. Proceedings before the FISC are ex parte, meaning the government is the only party present.

https://it.ojp.gov/PrivacyLiberty/authorities/statutes/1286

50 U.S. Code Chapter 36 - FOREIGN INTELLIGENCE SURVEILLANCE

• SUBCHAPTER I - ELECTRONIC SURVEILLANCE (§§ 1801 to 1813)
• SUBCHAPTER II - PHYSICAL SEARCHES (§§ 1821 to 1829)
• SUBCHAPTER III - PEN REGISTERS AND TRAP AND TRACE DEVICES FOR FOREIGN INTELLIGENCE PURPOSES (§§ 1841 to 1846)
• SUBCHAPTER IV - ACCESS TO CERTAIN BUSINESS RECORDS FOR FOREIGN INTELLIGENCE PURPOSES (§§ 1861 to 1864)
• SUBCHAPTER V - OVERSIGHT (§§ 1871 to 1874)
• SUBCHAPTER VI - ADDITIONAL PROCEDURES REGARDING CERTAIN PERSONS OUTSIDE THE UNITED STATES (§§ 1881 to 1881g)
• SUBCHAPTER VII - PROTECTION OF PERSONS ASSISTING THE GOVERNMENT (§§ 1885 to 1885c)

https://www.law.cornell.edu/uscode/text/50/chapter-36