Didja think that the legislative branch oversees the executive branch? Think again! Congress has no idea what the National Security Agency (NSA) is doing.

Spencer Ackerman at Wired’s Danger Room blog reports on a letter the inspector general of the intelligence community sent earlier this month to Senators Ron Wyden (D-OR) and Mark Udall (D-CO). They had asked how many people in the United States have had their communications collected or reviewed by the NSA.

The letter repeated the NSA IG’s conclusion that estimating this number was “beyond the capacity of his office and dedicating sufficient additional resources would likely impede the NSA’s mission.” Not only that, figuring out the number of people in the United States that the NSA has snooped on “would itself violate the privacy of U.S. persons.”

A federal agency can write a tart, dry non-response like this because Congress is utterly supine before the security bureaucracy. The tough-talking politicians in both parties have no idea what is happening in the agencies they routinely defend as essential. And Congress still hasn’t approved nominations for the Privacy and Civil Liberties Oversight Board, weak sauce that it is, nearly five years since it was reconstituted with greater independence and subpoena power.

The letter concludes with a hopeful note: “I will continue to work with you and the Committee to identify ways that we can enhance our ability to conduct effective oversight.” That also serves as a confession: We have no idea what the NSA is doing.