NSA operates in secret on behalf of a democratic republic that is deeply and properly distrustful of secrecy. The conduct of such a mission is tolerable only when it is performed in conformity with the laws and lawful orders of elected officials, and in the long run, only when the agencies that do it enjoy the nation's trust--trust in their competence and trust in their integrity. NSA has a foreign, not a domestic, intelligence mission, and this restriction is deeply ingrained in the Agency's leadership and workforce. The only time NSA may target the communications of a United States person13 in the United States is when there are reasonable grounds to believe such a person, acting on behalf of a foreign power, is knowingly engaging in, or is aiding or abetting, espionage, sabotage, or terrorism. And even then, there are laws and orders that dictate how the Agency must go about it. According to the Joint Congressional 9/11 Report, "Joint Inquiry interviews of a wide range of NSA personnel, from the Director down to analysts, revealed the consistent theme that NSA did not target individuals in the United States."14 That an intelligence agency should be singled out--even criticized--for its "cautious approach to any collection of intelligence in the United States"15 is an extraordinary turn of events.
It was not always so. Most of the laws, orders, and organizational changes that affect NSA's operations were put in place as a direct result of the spy scandals and resulting congressional investigations by the Church and Pike Committees in 1976.16 These investigations disclosed widespread abuses by the intelligence agencies, generally at the request of the executive. Most of them did not involve NSA, but some did--including spying on U.S. citizens for political purposes. As a result of that scandal the pressure for reform was intense, and in 1978 Congress passed the Foreign Intelligence Surveillance Act (FISA). That Act established a special court to hear applications for warrants permitting the interception of communications of specific U.S. persons within this country where there is probable cause to believe they are engaging in, or are aiding and abetting, espionage, sabotage, or terrorism on behalf of a foreign power. If the U.S. person is abroad, the Attorney General may authorize the collection under Executive Order 12333.
Sometimes NSA unintentionally acquires information to, from, or about U.S. persons in the course of targeting a foreign person abroad. Such incidentally acquired information may be retained and disseminated only under narrow circumstances. The information must satisfy a foreign intelligence requirement, and the identity of the U.S. person may be disseminated only if the identity is necessary to understand the foreign intelligence or assess its importance. NSA's Inspector General reports quarterly on all violations of these rules, whether intentional or accidental, to the chairman of the President's Intelligence Oversight Board. These reports not only serve an important external monitoring function; they also have a useful deterrent effect, because mistakes have to be explained, and no one likes to do that.