Footnote 14 should scare every American.

The footnote is contained in the just-declassified 2011 opinion by U.S. District Judge John Bates, then the chief judge of the Foreign Intelligence Surveillance Court.

In the ruling, Bates found that the government had been sweeping up e-mails before receiving court approval in 2008 and even after that was illegally collecting "tens of thousands of wholly domestic communications."

That's not the really scary part. This is: "The court is troubled that the government's revelations … mark the third instance in less than three years in which the government has disclosed a substantial misrepresentation regarding the scope of a major collection program."

Bates cited a 2009 finding that the court's approval of the National Security Agency's telephone records program was premised on "a flawed depiction" of how it uses metadata, a "misperception … buttressed by repeated inaccurate statements made in the government's submissions, and despite a government-devised and court-mandated oversight regime.

"Contrary to the government's repeated assurances, NSA had been routinely running queries of the metadata using querying terms that did not meet the required standard for querying. The court concluded that this requirement had been 'so frequently and systemically violated that it can fairly be said that this critical element of the overall … regime has never functioned effectively.' "

This is followed by two full paragraphs of redactions. We can only imagine what that episode entailed.

To judge the significance of Bates' footnote, it helps to know something about the judge. This is no wild-eyed liberal. He spent almost two decades in the U.S. Attorney's Office in Washington. He served as deputy to Independent Counsel Kenneth Starr during the investigation of President Bill Clinton. He was named to the bench by George W. Bush.

If Bates is worked up about being misled by the government, people should listen.

Security demands secrecy. The Constitution demands that secrecy be coupled with oversight. In theory, that oversight is twofold, from Congress and the judiciary, through the mechanism of the surveillance court.

In practice, oversight depends on some measure of good will from the overseen. No matter how diligent the overseers, particularly in an area as technologically murky and politically fraught as surveillance, the intelligence experts hold the cards.

Their deeply ingrained institutional bias is to reveal only what is absolutely necessary, to trust their secrets to as few outsiders as possible. When that instinct for secrecy edges into a willingness to mislead, effective oversight collapses.

We have already seen this on display before Congress, in the person of Director of National Intelligence James Clapper. In March, Sen. Ron Wyden asked Clapper whether the NSA "collects any type of data at all on millions or hundreds of millions of Americans." Clapper's answer, "No … not wittingly."

This was, as Clapper acknowledged, "clearly erroneous." His belated apology rings hollow. Clapper was not only forewarned about the question, he refused to correct his misrepresentation for months, until it was proved false.

So when Clapper, in announcing the new documents' release, asserts that they demonstrate "the government's serious commitment to getting it right," he hauls along a mountain of baggage.

It is possible to construct a happier narrative. After all, Bates' rebuke was prompted by the intelligence community's own disclosures. The government then cleaned up its act, with court-approved procedures to minimize privacy invasions. Congress was informed of the program, the court's problems with it and the fixes being made. The relevant documents were declassified and released (albeit in the face of a lawsuit). President Obama has proposed additional oversight mechanisms, such as building adversary procedures into the surveillance court.

These are hopeful signs, but they do not erase the ugly history: "repeated inaccurate statements" to the court, "clearly erroneous" congressional testimony.

Current assurances, made under the duress of unauthorized disclosure, must be judged in light of past performance.

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Ruth Marcus' column is distributed by the Washington Post Writers Group.