Margaret Sullivan writes: The ability of the press to report freely on its government is a cornerstone of American democracy. That ability is, by any reasonable assessment, under siege.

Reporters get their information from sources. They need to be able to protect those sources and sometimes offer them confidentiality. If they can’t be sure about that – and it looks increasingly like they can’t – the sources will dry up. And so will the information.

Sad to say, that seems to be exactly what the Justice Department has in mind with its leak investigations, two of which involve Times journalists. One has to do with the chief Washington correspondent David Sanger’s book and articles about American cyberattacks against Iran, the other is Scott Shane and Jo Becker’s article from last May about Mr. Obama’s “kill list.”

The Times’s executive editor, Jill Abramson, put it simply when I asked her about it Tuesday: “The press is supposed to hold government accountable. These investigations intrude on that process.”

The Times stories that are the subject of leak investigations “were in the great tradition of Washington reporting, helping people understand how decisions were made,” The Times’s newsroom lawyer, David McCraw, told me Tuesday. “There was no compromising of national security involved.”

“The net effect is universal,” he said. “People are less willing to talk, and that’s a loss for everyone.”

The Times is one of the many news and press rights organizations that signed a strongly worded letter sent to the Justice Department leadership on Tuesday.

This isn’t just about press rights. It’s about the right of citizens to know what their government is doing. In an atmosphere of secrecy and punishment – despite the hollow promises of transparency — that’s getting harder every day.