Congress’ days of allowing the administration to treat it as the least equal of the three co-equal branches may be coming to an end.

The House has filed a lawsuit challenging President Bush’s invocation of executive privilege to prevent former White House counsel Harriet Miers and White House Chief of Staff Joshua Bolten from testifying before Congress. The president not only told Miers and Bolten to withhold the information requested in the subpoenas, but he also refused even to allow them to appear before Congress or to identify the documents that they refused to supply.

Issued as part of Congress’ investigation into the 2006 forced resignations of several U.S. attorneys, the subpoenas have been stonewalled, first through months of foot-dragging in response to Congressional requests and then this assertion of executive privilege. In the face of an intransigent White House and a Justice Department that refuses to proceed with contempt of Congress prosecutions against Miers and Bolten, the House took matters into its own hands.

Despite Congress’ legitimate interest in investigating the reasoning behind some executive branch decisions, the president has dismissed the suit as a mere partisan Democratic fishing expedition. As a result, key questions remain unanswered and the executive branch has a new brick to add to its wall of secrecy.

Executive privilege serves a specific purpose: to encourage advisers to provide the president with candid advice on official matters. This means information should be shielded only if it is used in advising the president. The decision to force out certain U.S. attorneys simply does not — by the White House’s own admission — fall into this category.

By invoking privilege to avoid appearing before Congress, Miers and Bolten deny Congress the opportunity to determine whether the information at issue is even entitled to privilege. Instead, the president acted as judge and jury of his own privilege claim, undermining Congress’ oversight authority and thwarting efforts to investigate potential misdeeds in the executive branch.

There’s one tiny problem with the executive privilege claim — it cannot be justified by history or reason.

Executive privilege does not automatically attach to every word uttered and every document drafted by an adviser. There are, after all, 400 to 500 members of the White House staff, and twice that number in the Executive Office of the President. And even more senior advisers play a variety of roles. So it cannot be the case that all communications involving presidential advisers are protected by executive privilege.

Indeed, the privilege claim here flies in the face of both past practice and logic. Advisers regularly have appeared before committees to assert the privilege over testimony and documents. During an investigation of the dismissals of White House Travel Office employees, the Clinton administration provided a detailed log listing the documents withheld on executive privilege grounds. Just last year, former White House Political Director Sara Taylor appeared as part of this same U.S. attorney investigation, answering some of the committee’s questions and asserting executive privilege in response to others.

The administration’s position is all the more untenable given the repeated assurances that the president himself had no role in the forced resignations at issue. If the president was not involved in the decision-making process, then the communications leading to the firings can hardly be considered to be privileged.

Apparently, the president’s advisers, like this administration’s interrogators and wiretappers, are not expected to play by the same rules as everyone else. But there have been serious and substantial allegations of impropriety. No one suggests these allegations are frivolous. They demand thorough investigation, without which confidence in the rule of law will be undermined. Without the information sought in the subpoenas, a real inquiry simply cannot take place.

If the courts fail to find in Congress’ favor and instead allow the executive branch to assert such blanket privilege, they will set a precedent that lawlessness, lack of accountability and lack of oversight is acceptable now, and from future presidents as well.

Emily Berman is counsel and Katz fellow in the Brennan Center for Justice Liberty & National Security Project. Maggie Barron is the center’s communications associate.