In dim Mexican restaurants, behind abandoned schools, and on nameless suburban street corners, I met some of the bravest people that I have ever known.

And I can’t tell you the name of a single one of them.

During my seven years as a professional journalist, these sources gave me information about government corruption, nonprofit mismanagement, and corporate malfeasance. They had little to gain and much to lose, including their jobs, savings, and freedom. All they asked was that I promise not to reveal their names, even if compelled by a court. I obliged, and they took me at my word.

Countless other journalists have made such confidentiality promises for more than a century. Although the journalists faced the prospect of jail, they knew that they could challenge a subpoena in court and force the government to explain why its need for the information outweighs the public interest in maintaining confidentiality.

That entire system collapsed yesterday when it became public that the U.S. Justice Department had obtained call records for more than 20 telephone extensions of Associated Press journalists.

In light of this revelation, journalists can no longer be assured that their sources’ names will remain confidential. Even if journalists are willing to face jail and heavy fines, the government still could obtain source information without the journalist having the opportunity to challenge a subpoena.

We have long known that such spying was possible. For years, Lucy Dalglish, the former head of the Reporters Committee for Freedom of the Press who is now dean of the University of Maryland Philip Merrill College of Journalism, warned that the government would no longer issue subpoenas; it would simply spy on journalists.

Until yesterday, I attempted to minimize Lucy’s concerns. I graduated from law school a few years ago, and my professors generally painted a rosy picture of our constitutional system. Yes, there will always be an adversarial relationship between the government and the Fourth Estate, but the First Amendment exists to protect against such abuses.

Except when the government ignores it.

Yesterday’s news demonstrates that our Constitution is only as strong as the government that serves under it. The First Amendment makes our government great, but our government must make the First Amendment great.

In third-world dictatorships, it would have been impossible for me to promise confidentiality to sources, particularly if they were disclosing negative information about the government. But we are not a third-world country. We are a country where Henry Demarest Lloyd, Upton Sinclair, Rachel Carson, Seymour Hersh, Dana Priest, and many other investigative journalists made our nation greater by exposing its greatest weaknesses. As Justice Hugo Black wrote, the Founding Fathers “gave the free press the protection it must have to fulfill its essential role in our democracy.”

Without the ability to guarantee confidentiality to sources, the entire Fourth Estate, as envisioned by our Framers, is undermined.

This is not only a sad week for journalists; it is a sad week for the nameless and faceless brave sources who have stories to tell and for the public, which will lose the opportunity to hear those voices.

The author, Jeff Kosseff, is an attorney at Covington & Burling who was a finalist for the Pulitzer Prize in 2007 as a reporter for The Oregonian. Jeff practices in the privacy and media groups and represents the Newspaper Association of America in its efforts to enact a federal shield law.  The views expressed are those of the author and not of the firm.