Those who wish to keep the internet free and open had best dust off their legal arguments. One of America's most influential conservative judges, Richard Posner, has proposed a ban on linking to online content without permission. The idea, he said in a blog post last week, is to prevent aggregators and bloggers from linking to newspaper websites without paying:

Expanding copyright law to bar online access to copyrighted materials without the copyright holder's consent, or to bar linking to or paraphrasing copyrighted materials without the copyright holder's consent, might be necessary to keep free riding on content financed by online newspapers from so impairing the incentive to create costly news-gathering operations that news services like Reuters and the Associated Press would become the only professional, nongovernmental sources of news and opinion.

Posner's notion set off an eruption from the likes of Jeff Jarvis, Matt Welch and Erick Schonfeld, among others. And they are right to be furious. Not only would Posner stop online media dead in their tracks, but he would also overturn long-established rules of fair use, which, among others things, allow for the reproduction of short excerpts of copyrighted material for the purposes of commentary, parody and the like – precisely what bloggers and aggregators do all the time.

And Posner, who sits on the seventh circuit court of appeals in Chicago, has a way of getting his way. A brilliant, provocative thinker and a frighteningly prolific writer, he was described in a 2001 New Yorker profile as "the most mercilessly seditious legal theorist of his generation". And if, at 70, Posner and his generation are not quite so influential as they once were, he is still a formidable presence on the legal scene.

In something of an irony for journalists who might be inclined to cheer Posner's latest, it was a 2003 opinion he wrote that helped cement journalists' modern status as cultural and social pariahs. Posner's decision in the case of McKevitt v Pallasch did more than any other to vanquish the idea that journalists called into court had some protection under the first amendment from having to reveal their confidential sources.

For a generation, journalists and their lawyers had relied upon the hazy wording of a 1972 supreme court case called Branzburg v Hayes, in which a bare majority ruled there was no reporter's privilege. One of the majority, Lewis Powell, wrote what his fellow justice Potter Stewart called "an enigmatic concurring opinion" suggesting that maybe, in some cases, there was a privilege. As retired New York Times lawyer James Goodale explained in the Frontline documentary News Wars several years ago, media lawyers used Powell's opinion to keep the reporter's privilege on life support for more than 30 years until Posner, finally, pulled the plug.

As an appeals court judge, Posner could not, of course, overrule the supreme court. In McKevitt, though, he didn't have to: he wrote that he had reread Branzburg and had come to the conclusion that, lo and behold, it meant what it said. No more reporter's privilege, although the states were free to create their own through shield laws and state court precedents. (All except Wyoming have done so, many of them long before McKevitt. And Congress may create a federal shield law later this year.)

Posner's opinion on copyright – expressed, thankfully, in a blog post rather than a ruling from the bench – has its roots in a celebrated essay he wrote for the New York Times Book Review in 2005 called Bad News. Although Posner was complimentary toward bloggers, and even asserted that their swarm-like verification system was superior in some ways to that of the traditional media, he nevertheless offered a few withering observations about where they get their material.

"The bloggers are parasitical on the conventional media," Posner wrote. "They copy the news and opinion generated by the conventional media, often at considerable expense, without picking up any of the tab. The degree of parasitism is striking in the case of those blogs that provide their readers with links to newspaper articles. The links enable the audience to read the articles without buying the newspaper."

Posner comes across as willfully blind to the ways in which bloggers and aggregators actually drive traffic to news sites, resulting in more readers seeing their content and, thus, their advertising. Yes, there are ways not to do it – the Boston Globe's wholesale, automated aggregation of a competitor's local content in a case settled out of court earlier this year comes to mind. But normal linking practices benefit everyone. The news business may be cratering, but it's not the fault of those who link to newspaper content.

Fortunately, Posner this time can't transform his desires into a judicial decree – his proposal would have to enacted in the form of an amendment to the copyright law. Unfortunately, such an idea is already making the rounds. Not to go all Kevin Bacon here, but Cleveland Plain Dealer columnist Connie Schultz, who supports it, is married to Democratic senator Sherrod Brown, which led Jeff Jarvis to demand that Schultz register as a federal lobbyist.

The thing is, Congress has been known to act with great alacrity on copyright matters when they affect corporate interests. And newspaper owners have been remarkably successful in calling attention to their plight.

But though tax breaks, special non-profit status and other federal goodies will likely go nowhere, a law aimed squarely at the linking practices of sites such as Google News and the Huffington Post would probably prove popular, the facts be damned.

It's ominous that those would push for such a law now have an ally as brilliant and influential as Posner. Keep a close eye on this one.