Geof Stone, "Reflections on the FISA Court"
Before 1978, the federal government assumed that agencies like the NSA and the FBI could legally carry out wiretaps and other forms of electronic surveillance against suspected foreign intelligence agents inside the United States without any prior judicial approval. The assumption was that the invocation of "national security" was sufficient to override the Fourth Amendment's ordinarily strong presumption that any such surveillance must be authorized in advance by a judicial warrant finding that the proposed surveillance is legal.
In 1978, as a result of disclosures about Nixon-era abuses uncovered by the Church Committee, Congress enacted the Foreign Intelligence Surveillance Act which, among other things, created the Foreign Intelligence Surveillance court. Although Congress recognized that government investigations of foreign agents for national security purposes often necessitated a heightened degree of secrecy, it also recognized that prior judicial approval of such surveillance was an essential safeguard against abuse whenever the surveillance might affect an American citizen.
The compromise was to create a court that would have to approve foreign intelligence surveillance activities, but could do so in a manner that would protect the need for secrecy. In short, the creation of the FISA court was a major reform designed to provide for much-needed independent judicial oversight of foreign intelligence investigations. The FISA Act of 1978 was thus seen as a critical step forward in the effort to preserve our civil liberties.