As Congress begins to investigate allegations concerning the destruction of videotapes of detainee interrogations by the C.I.A., there are questions that arise concerning the ability of Congress to engage in effective oversight of executive branch agencies in the area of national security. The Department of Justice has already pushed back and asked Congress to stay its inquiries into the destruction of the tapes, citing potential interference in the concurrent criminal inquiries initiated by the Department.

This well known Kabuki dance between Congress and the Executive branch over the intersection between oversight and criminal law enforcement has played out hundreds of times since the beginning of the Republic, in our lifetimes most notably in Watergate and Iran-Contra. There is an equally insidious way in which these shared investigative powers collide—and that is in the way in which the Executive seeks to control and intimidate Congressional oversight by reliance on the classification system and the veiled, and sometimes direct, threat of prosecution of members of Congress for disclosing classified information in the course of performing their oversight responsibilities.

One such recent episode illustrates the way in which this threat unduly and illegitimately inhibits the kind of oversight Congress should be doing in this area. In 2003, Senator Jay Rockefeller, the ranking Democrat on the Senate Intelligence, felt compelled to write a handwritten secret letter to the Vice President expressing his concerns about the Executive’s surveillance program. See Charles E. Schumer: Under Attack: Congressional Power in the Twenty-First Century . According to media stories at the time, Senator Rockefeller felt constrained to use this low key fully private approach for fear that a more robust formal official channel would have been subjected to charges that he violated strictures on the disclosure of classified information.

Of course, from a constitutional and legal prospective, any such fear was unfounded, as established by the landmark Vietnam era case Gravel v. United States .

On June 29, 1971 Senator Gravel  convened a night-time meeting of the subcommittee on Buildings and Grounds, which he chaired, and placed the 47 volumes of the Pentagon Papers (a study of the causes and conduct of the Vietnam war) into the public record. The Justice Department commenced a grand jury investigation into possible criminal conduct in the release and publication of the study by Beacon Press and subpoenaed an aide to the senator. Senator Gravel intervened on his behalf and asserted that questioning the aide about his involvement in the committee hearing or the subsequent publication by Beacon Press contravened the Constitution’s “speech or debate” clause, which provides immunity to Members of Congress for their performance of legislative acts. The Court held that neither the Senator, nor his aide, could be questioned concerning their preparations for the hearing, communications between the Senator and aides relating to that meeting or anything said or done at the hearing. The Court also held that the grand jury could question the arrangements with Beacon Press concerning private publication of the Pentagon Papers because efforts to disseminate the study outside of Congress didn’t constitute protected legislative activity.

The Court protected the conduct of the hearing, even though the hastily convened night-time meeting was a none too subtle attempt to shield the dissemination of classified material, and even though such acts of dissemination, if performed outside of Congress, would be subject to criminal prosecution.

Under Gravel, Senator Rockefeller (nor any other member of Congress) need not have been either so secretive or reticent to use official channels to question the surveillance program, or for that matter any other subject of national security. Indeed, he could have officially communicated with relevant Executive officials, shared that correspondence with his colleagues on the Committee, or even taken to the Senate floor to speak about the issue. (Whether such conduct would have been consistent with Senate and Committee rules governing classified information would be a matter only for the Senate and could play no part in any Executive branch examination of his conduct). The "Speech or Debate" clause protection is based on its English antecedent, the product of several centuries struggle by Parliament to attain independence from the Crown. In this country it was adopted without debate at the constitutional convention to provide the same independence to legislators to be free from intimidation by the executive, or accountability before the judiciary.

The Rockefeller episode illustrates how too often legislators are cowed into acquiescence or timid supplications with respect to issues involving classified documents or matters by an aggressive or threatening Executive branch. Of course, over 30 year ago in a case eerily reminiscent of the current controversies, the Supreme Court laid to rest the notion that legislators could be questioned by the Executive branch for doing their job. Every member of Congress needs to read the Gravel decision to appreciate the broad constitutional protection they have been afforded by the Framers to inquire into the Executive’s administration of our national security apparatus.