The senators on the judiciary committee are likely to make repeated reference to Justice Robert H. Jackson's canonical concurring opinion in Youngstown Sheet and Tube Company v. Sawyer -- the 1952 Supreme Court decision holding that President Truman lacked authority to seize the nation's steel mills in order to prevent a labor strike that threatened arms production for the Korean War. According to the system that Jackson laid out, when Congress has expressly authorized the president to act, "his authority is at its maximum." When Congress has expressly or implicitly told him not to act, then "his power is at its lowest ebb." In between is when Congress is silent -- what Jackson memorably called the "zone of twilight." In this situation, the status of presidential action is uncertain and is therefore likely to be decided not by law but by political circumstances and practical considerations.

As to what effect Monday and future hearings can have, Prof. Feldman lists two: providing a debate forum for Americans as to how far Bush can push the extent of his authority as President and sending a signal to courts that may be confronted in the future with deciding cases on the NSA program.

The Senate is sometimes derided as a mere debating chamber, but in this case, debate is exactly what we need. For the last five years, with a Republican-controlled Congress, Americans have not been exposed to serious Congressional debate on any major issue, let alone how far the executive branch may go in protecting our security. These hearings -- called by a Republican, Senator Arlen Specter -- will afford us the first major opportunity to hear and (via our representatives) air legitimate concerns about whether the president has gone too far.

Furthermore, the committee's debate will have an indirect effect on the courts. When the eavesdropping issue finally does come before a court -- as it seems likely to by one route or another; two civil rights groups recently filed lawsuits against the administration over its domestic spying program -- the judges who address it will be aware of what happened in the hearings and of the public debate surrounding them.

But what practical effect can result from the hearings? While acknowledging that the hearings can't undo the surveillance conducted to date, Prof. Feldman lists three:

• "[The Senators] can express outrage (in a resolution or on the floor) that the president saw fit to usurp Congress's power to set the ground rules for secret surveillance."

• "Congress could pass legislation invalidating the executive order authorizing the eavesdropping and thus set the stage for a potential constitutional battle that would move to the courts. "

• "Congress [could] conclude that new laws actually are needed for the war on terror -- but it could pass those laws itself instead of letting the president make them up as he goes along."

As I wrote previously, let's not rush to amend FISA to give the Government more snooping power over Americans. I hope the Democrats, out of fear of being perceived as being soft in the war on terror, don't pander to the public and insist at the hearing that they would have granted the President the power he exercised unilaterally had he only asked.

Given this assessment of the program, it's ineffective at best, and a civil liberties-stripping measure at worst. We don't need to amend FISA to permit worthless but intrusive spying on Americans. We need to call a spade a spade, and just denounce Bush's program as an illegal power grab.