The Federal Bureau of Investigation has checked out thousands, perhaps tens of thousands, of leads of potential terrorists who have turned out to be innocent Americans, according to a recent news story.

The work has at times placed a heavy burden on the agency and may have caused its director to doubt that the information it was being given, from a secret eavesdropping program at the National Security Agency, “had a proper legal foundation.” Whether the president is authorized to order this wiretapping, as the White House maintains, or has overstepped his authority, Congress needs no better reason to intervene than the apparent conflict in direction of these two intelligence agencies.

The New York Times reported last week on the conflict, quoting an FBI official who said the agency’s director, Robert Mueller, raised concerns with the administration about the legal basis of the program. The news story quoted one former FBI official saying, “We’d chase a [telephone] number, find it’s a school teacher with no indication they’ve ever been involved in international terrorism – case closed. After you get a thousand numbers and not one is turning up anything, you get some frustration.” Vice President Dick Cheney and others in the White House have said how important this program is, that for all the dead ends there has been enough useful information to justify the program.

Republican Sen. Arlen Specter said the Senate Judiciary Committee would thoroughly investigate the issue, but he has already doubted one argument used by the administration to assert its right to wiretap without warrants. Attorney General Alberto Gonzales has said Congress implied that authority when it passed a measure soon after 9-11 to allow the president “to use all necessary and appropriate force” against terrorism, an assertion repeated in a Justice Department white paper Jan. 19. Sen. Specter told Reuters that if the White House were relying on that measure, “I thought they were wrong.”

There must be better arguments for the president’s authority in this area, but repeated use of an argument the chairman of the Judiciary Committee finds specious on its face highlights the importance of congressional review no matter what those may be.

Who is being monitored and how are their rights being upheld, what happens to the data afterward, how is the information being verified or discounted, who keeps records on it and for what use are basic questions about Americans’ right to privacy. Protection of this right in regard to the data-mining program seems minimal, and while there are many reasons for keeping at least some of the NSA process secret, oversight should not begin and end in a single branch of government. The congressional role is crucial.

Sen. Specter appears more than capable of running a fair and probing hearing on these issues. He should, but may not, receive support from the White House in this pursuit; he absolutely depends on the interest of the public in recognizing what is at stake.