NO GOVERNMENT can function without secrets. In national security, they are necessary to protect military operations, intelligence sources and methods, and sensitive deliberations and communications. The United States has created a system that gives about 4.8 million people, both government employees and contractors, access to classified materials, labeled confidential, secret or top secret.

J. William Leonard knows this system well. He served in the Defense Department, where in the 1990s he had responsibility for policies on classified information, and from 2002 to 2008 he was the director of the Information Security Oversight Office, the “classification czar.”

Mr. Leonard was hoping to be an expert witness at the trial of Thomas Drake, a former National Security Agency official charged in 2010 with 10 felony counts for passing information to a Baltimore Sun reporter in 2006 and 2007. The case collapsed in June 2011; Mr. Drake agreed to plead guilty to a single misdemeanor of exceeding the authorized use of his government computer.

As a result, Mr. Leonard never got to testify. But he had something important to say about the system of keeping secrets at a time when so much concern is being expressed about leaks.

A document at the center of the Drake case was a classified e-mail summarizing an agency meeting. The e-mail was titled “What a Wonderful Success.” It is an innocuous, self-congratulatory message to a team for its presentation to the director, Gen. Keith Alexander. Two paragraphs were classified “secret.” Now that the e-mail has been released, everyone can see what was so sensitive. One of the paragraphs included the hush-hush fact — be careful if you finish reading this sentence — that Gen. Alexander left a conference room and greeted people in a lab who had worked to make sure the demonstration was a success.

According to an affidavit by Mr. Leonard, the e-mail “contained no information which met the standards of the classification system.” He added, “I have seen many equally egregious examples of inappropriate assignment of classification controls to information that does not meet the standards for classification; however, I was prepared to testify that I have never seen a more willful example.”

He subsequently told Ellen Nakashima of The Post that the episode underscores how our classification system is becoming “dysfunctional.” Mr. Leonard added, “Specifically, the system clearly lacks the ability to differentiate between trivial information and that which can truly damage our nation’s well-being.” He pointed out that while people with clearances are being punished for disclosing supposedly classified information, almost no one is ever punished for over-classification.

The more that classification is used to hide the trivial, inconvenient or embarrassing, the less useful it is for genuine national security secrets. A democracy needs to balance secrecy with openness. While leaks can be damaging, excessive concealment is also corrosive, undermining trust and credibility in the very policies that the government seeks to protect.