The subpoena served on St. Louis Public Radio Thursday is both baffling and disturbing.

It arrived the day after the Board of Aldermen's Public Safety Committee hearing devolved into shouting and shoving. The topic under discussion was a plan for a civilian review board for police. Police union representative Jeff Roorda, accompanied by union members, was among those present when the scuffle broke out. No arrests were made at the meeting, but police announced Thursday they would investigate complaints.

The subpoena commands us to provide: “All raw and aired video and audio footage of the meeting ... including footage of interviews, the meeting itself and any events that occurred in the meeting room or in the area outside the meeting room. We are further requesting any and all handwritten notes and/or names of witnesses contained in said footage, coverage and articles from January 28, 2015 to the present,” it says.

Then it asks us to keep the whole thing mum, saying: “Pursuant to Sections 540.110 and 540.120, RSMo, you are requested not to disclose the existence of this subpoena or that you have provided information pursuant to this subpoena. Such disclosure would impede investigation at this time.” Those statutes relate to secrecy of grand jury proceedings and do not require that subpoenas be kept secret.

What's baffling is this: Why subpoena a news organization for information when this was a public meeting with many witnesses present, including several police officers? Why assert that public disclosure of the subpoena would impede the investigation when the investigation was publicly announced?

There are good reasons why news organizations generally resist turning information over to authorities – and why prosecutors usually force news organizations to get involved only as a matter of last resort. Freedom of the press is a constitutional right – guaranteed because the country's founders recognized that it's essential for keeping the public informed and for checking abuses of power. When prosecutors seek journalists' notes, images and recordings, that impedes their ability to function.

You've seen news organizations playing a vital role in the aftermath of Michael Brown's death in Ferguson. Though the work has been far from perfect, reporters and photographers have been crucial in helping St. Louisans and the world understand what's happening, what's at stake, what's fact and what's rumor.

Sometimes, the journalists have faced hazards or even threats as they've witnessed looting or found themselves in the midst of confrontations between protesters and police. How much riskier will that work become if people think everything journalists observe will end up in the hands of prosecutors?

There has been long and vigorous debate over whether reporters should have an absolute right to shield sources and information. But you need not resolve that question to see that it's a mistake to subpoena St. Louis Public Radio in this case. Authorities have many other ways to obtain information. And the public has much to lose if the functioning of the press is compromised.

That's why this particular subpoena is so disturbing. And the “request” to keep it secret makes it even more so. When public interests are at stake, then public scrutiny and debate are essential. It's unreasonable to take action that could impinge on the ability of news organizations to serve the public, then ask that the public be kept in the dark.

Soon after it arrived, St. Louis Public Radio reported the existence of the subpoena. We will continue to do our best to keep St. Louisans well informed.