President Bush's post- Sept. 11, 2001, authorization to the National Security Agency to carry out electronic surveillance into private phone calls and e-mails is consistent with court decisions and with the positions of the Justice Department under prior presidents.

The president authorized the NSA program in response to the 9/11 terrorist attacks on America. An identifiable group, Al Qaeda, was responsible and believed to be planning future attacks in the United States. Electronic surveillance of communications to or from those who might plausibly be members of or in contact with Al Qaeda was probably the only means of obtaining information about what its members were planning next. No one except the president and the few officials with access to the NSA program can know how valuable such surveillance has been in protecting the nation.

In the Supreme Court's 1972 Keith decision holding that the president does not have inherent authority to order wiretapping without warrants to combat domestic threats, the court said explicitly that it was not questioning the president's authority to take such action in response to threats from abroad.

Four federal courts of appeal subsequently faced the issue squarely and held that the president has inherent authority to authorize wiretapping for foreign intelligence purposes without judicial warrant.

In the most recent judicial statement on the issue, the Foreign Intelligence Surveillance Court of Review, composed of three federal appellate court judges, said in 2002 that "All the ... courts to have decided the issue held that the president did have inherent authority to conduct warrantless searches to obtain foreign intelligence ... We take for granted that the president does have that authority."

The passage of the Foreign Intelligence Surveillance Act in 1978 did not alter the constitutional situation. That law created the Foreign Intelligence Surveillance Court that can authorize surveillance directed at an "agent of a foreign power," which includes a foreign terrorist group. Thus, Congress put its weight behind the constitutionality of such surveillance in compliance with the law's procedures.

But as the 2002 Court of Review noted, if the president has inherent authority to conduct warrantless searches, "FISA could not encroach on the president's constitutional power."

Every president since FISA's passage has asserted that he retained inherent power to go beyond the act's terms. Under President Clinton, deputy Atty. Gen. Jamie Gorelick testified that "the Department of Justice believes, and the case law supports, that the president has inherent authority to conduct warrantless physical searches for foreign intelligence purposes."

FISA contains a provision making it illegal to "engage in electronic surveillance under color of law except as authorized by statute." The term "electronic surveillance" is defined to exclude interception outside the U.S., as done by the NSA, unless there is interception of a communication "sent by or intended to be received by a particular, known United States person" (a U.S. citizen or permanent resident) and the communication is intercepted by "intentionally targeting that United States person." The cryptic descriptions of the NSA program leave unclear whether it involves targeting of identified U.S. citizens. If the surveillance is based upon other kinds of evidence, it would fall outside what a FISA court could authorize and also outside the act's prohibition on electronic surveillance.

The administration has offered the further defense that FISA's reference to surveillance "authorized by statute" is satisfied by congressional passage of the post-Sept. 11 resolution giving the president authority to "use all necessary and appropriate force" to prevent those responsible for Sept. 11 from carrying out further attacks. The administration argues that obtaining intelligence is a necessary and expected component of any military or other use of force to prevent enemy action.

But even if the NSA activity is "electronic surveillance" and the Sept. 11 resolution is not "statutory authorization" within the meaning of FISA, the act still cannot, in the words of the 2002 Court of Review decision, "encroach upon the president's constitutional power."

FISA does not anticipate a post-Sept. 11 situation. What was needed after Sept. 11, according to the president, was surveillance beyond what could be authorized under that kind of individualized case-by-case judgment. It is hard to imagine the Supreme Court second-guessing that presidential judgment.

Should we be afraid of this inherent presidential power? Of course. If surveillance is used only for the purpose of preventing another Sept. 11 type of attack or a similar threat, the harm of interfering with the privacy of people in this country is minimal and the benefit is immense. The danger is that surveillance will not be used solely for that narrow and extraordinary purpose.

But we cannot eliminate the need for extraordinary action in the kind of unforeseen circumstances presented by Sept.11. I do not believe the Constitution allows Congress to take away from the president the inherent authority to act in response to a foreign attack. That inherent power is reason to be careful about who we elect as president, but it is authority we have needed in the past and, in the light of history, could well need again.

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John Schmidt served under President Clinton from 1994 to 1997 as the associate attorney general of the United States. He is now a partner in the Chicago-based law firm of Mayer, Brown, Rowe & Maw.