A U.S. federal law regulating the way that U.S. intelligence agencies conduct foreign intelligence surveillance activities, including wiretaps and the interception of communications. The act sets forth a judicial approval process required when the government targets U.S. persons located within the United States. FISA allows warrantless surveillance to be conducted without a court order for up to one year, provided the surveillance is for foreign intelligence information, is targeting foreign powers and will not capture the contents of any communication to which a U.S. person is a party. Generally speaking, FISA does not apply to activities directed at persons overseas.
Link to text of law: Foreign Intelligence Surveillance Act of 1978