The Foreign Intelligence Surveillance Act of 1978 recognized clandestine foreign intelligence gathering as a legitimate function of the government in the national security interest, but also worked to set up a legal regimen to govern this effort.

The Foreign Intelligence Surveillance Court, created under the act, is made up of seven federal district court judges from around the country. The first court of judges were cleared and appointed by Chief Justice Warren Berger and began work on May 18, 1979.

Under FISA, all requests to conduct electronic eavesdropping surveillance must be reviewed by the Justice Department, approved by the Foreign Intelligence Surveillance Court, certified by the attorney general and reported to the House Permanent Select Committee on Intelligence and the Senate Select Committee on Intelligence.

FISA also requires that the target of the surveillance be "a foreign power or an agent of a foreign power" and that "the purpose of the surveillance is to obtain foreign intelligence information" and nothing more.

But the act also set a different set of standards to allow for more aggressive surveillance in times of emergency.

FISA allows for the attorney general to immediately implement a surveillance activity by notifying the court and then presenting a written application within 24 hours. If the application is not approved by the FISC judge, the surveillance must be terminated.

In the event of war, FISA grants warrantless wiretaps for a limited time period. "Notwithstanding any other law, the president, through the attorney general, may authorize electronic surveillance without a court order under this subchapter to acquire foreign intelligence information for a period not to exceed 15 calendar days following a declaration of war by the Congress," the law reads.

FISA does allow for surveillance on people within the United States but only if the surveillance target is an agent of a foreign power, involved in international terrorism or is knowingly helping someone who is an agent of a foreign power or terrorist. The FISC must also ensure that the request would not impinge on the individual's Fourth Amendment rights.

Domestic surveillance subject to stricter rules
Stricter rules apply for domestic intelligence surveillance because U.S. citizens are protected by the Fourth Amendment of the Constitution which guarantees "the right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures."

Eavesdropping on U.S. Citizens is also viewed as an intrusion on the First Amendment rights of privacy and speech. Domestic surveillance rules require that the government first show "probable cause" that a crime has been or is about to be committed.

Fourth Amendment protections are less clear when it comes to surveillance of foreigners for national security purposes.

Warrantless electronic surveillance of foreign powers has historically been a tool of presidents during war time or time of international tension. President Franklin Roosevelt conducted wire taps prior to World War II and the use of electronic eavesdropping by U.S. intelligence agencies expanded greatly during the Cold War in the 1960s and 1970s.

However, events during the Nixon administration raised concerns about the abuse of presidential power when conducting wiretaps.

Nixon era abuses
In the late 1960s and early 1970s, President Nixon was concerned about unrest caused by the ongoing war in Vietnam War and the civil rights movement. Nixon asked the CIA and the National Security Agency, intelligence organizations charged with foreign surveillance, to eavesdrop on U.S. Citizens The domestic spying program targeted the political activities of members of the anti-war and civil rights movements including singer Joan Baez, the family of Martin Luther King Jr. and members of a group called the White Panthers.

The White Panthers were charged with bombing a CIA office in Michigan in 1968. During the trial, prosecutors submitted into evidence conversations taped by federal agents without a warrant on the authority of President Nixon's attorney general, John Mitchell.

In 1971, Mitchell submitted a sworn statement defending his actions saying the surveillance was necessary to protect the nation from "attempts of domestic organizations to attack and subvert the existing structure of the government."

However, the Supreme Court disagreed. In 1972 the Supreme Court ruled unanimously to prohibit warrantless electronic surveillance of domestic organizations. The freedoms protected by the Fourth Amendment "cannot properly be guaranteed if domestic security surveillance may be conducted solely within the discretion of the executive branch," wrote Justice Lewis Powell, a Nixon appointee.

More intelligence abuses came to light during the Watergate investigation and in a lengthy New York Times article by Seymour Hersh published in 1974. As a result, the Senate convened a special investigative committee headed by Sen. Frank Church, D-Idaho, to investigate the intelligence abuses.

Convinced that congressional oversight of the intelligence community was necessary to protect the public from such abuses, the intelligence committee later became a permanent fixture of both the House and Senate.

Amendments to FISA
FISA has been amended at times to incorporate advances in communications technology. For example, a 1998 amendment expanded the activities allowed under FISA to include pen register/trap and trace devices, provided they targeted "an agent of a foreign power."

A pen register collects the outgoing phone numbers placed from a specific telephone line, a trap and trace device collects incoming numbers. Caller ID is an example of a trap and trace device.

More significant changes came after the attacks of Sept. 11, 2001 and as a result of the USA Patriot Act passed a month later.

Initially, FISA required that foreign intelligence information gathering be the sole or "primary purpose" of electronic surveillance. The Patriot Act expanded the application of FISA to situations where foreign intelligence gathering is only "a significant" purpose of the investigation. Significant is not defined and is subject to interpretation by the FISC.

FISA originally required separate surveillance applications for each device or phone number to be targeted. The Patriot Act expanded FISA rules to permit "roving wiretap" authority, which allows communications surveillance to follow the intelligence target as he or she moves from device to device, for example, home phone, to cell phone, to computer.

The Patriot Act also expanded the use of pen register/trap and trace device orders to "any investigation to gather foreign intelligence information," without having to establish that the device has, or will be used by "an agent of a foreign power."

Other major changes to FISA as a result of the Patriot Act were changes to rules limiting intelligence sharing. Prior to the Patriot Act, the FISC had interpreted FISA as mandating a "wall" that prevents the sharing of information gathered during intelligence surveillance in a criminal investigation.

After passage of the Patriot Act, then Attorney General John Ashcroft issued guidelines on information sharing that directed law enforcement officials, including the FBI and federal prosecutors, to immediately notify the CIA and the Department of Homeland Security or other U.S. Intelligence community officials of any intelligence information collected as the result of a criminal investigation.

The guidelines also call for the attorney general and federal criminal prosecutors to consult with intelligence officials and to help direct intelligence investigations.

Due to an increase in the number of surveillance requests after the attacks of 9/11, the number of judges on the FISC was expanded from seven to 11. To make emergency applications easier, three of the judges must be located within 20 miles of Washington, D.C.

The time allowances for emergency circumstances also have been expanded after 9/11. The attorney general now has 72 hours to submit an application for a warrant after implementing an emergency surveillance, instead of the previous 24 hour requirement.

-- Compiled by Anne Bell for the Online NewsHour