Dr Stephen Barrett, a journalist who runs a website dedicated to exposing health frauds, had sued Ilena Rosenthal, director of the Humantics Foundation, which campaigns against breast implants, over critical personal comments Rosenthal posted to an internet newsgroup she runs. They were not, in fact, her own words but were pasted from an e-mail sent to her by someone else. Nevertheless, Dr Barrett alleged, Rosenthal was liable as she posted the comments even after he had warned her that they were false and defamatory.

In the UK, Dr Barrett probably would have won the case. In California, he lost. The court ruled that the person claiming libel must sue the individual who made the comment in question, not the person or company who allowed it to be published.

The case centred on section 230 of the Communications Decency Act, which states that "no provider or user of an interactive computer service shall be as the publisher or speaker of any information provided by another information content provider".

According to the judge, Justice Carol Corrigan, this law had been drafted to protect free speech. "The prospect of blanket immunity for those who intentionally redistribute defamatory statements on the internet has disturbing implications," she wrote. "Nevertheless, by its terms section 230 exempts Internet intermediaries from defamation liability for republication. The statutory immunity serves to protect online freedom of expression and to encourage self-regulation, as Congress intended."

In my view, the law goes too far.

In Europe, there is protection for internet intermediaries written into the E-Commerce Directive, but it is qualified. If a website allows users add content without it first having passed through an editor and a user then posts material that is defamatory, the host is generally not liable. The same applies in the US, but in Europe the operator also has a duty to remove or block access to defamatory material as soon as someone complains about it. They could be sued if they fail to react quickly.

In the US, on the other hand, section 230 protects both the operator and, remarkably, the defamatory material. The result is that you can sue an individual for defamation but you cannot force a third party to remove those comments from their website.

This is bizarre. The US approach to copyright mirrors our own — if you copy the text of a website without permission and pastes it to your own site, you can be sued and forced to remove the offending content — so why not extend this approach to libellous material?

Judge Corrigan considered this. If US service providers were put in the same position as their UK counterparts, it would "create an impossible burden", she reasoned: they would have to investigate each complaint. Yet that is exactly what service providers in Europe do. It is a burden, without question, but it is a necessary one. Surely a mechanism that offers redress against defamation is defective if it fails to stop the harm continuing?

Rosenthal is not even a service provider; she is an individual, so there would be no such obstacle. Judge Corrigan noted some of the differences: "In particular, individuals do not face the massive volume of third party postings that providers encounter," she wrote. "Self-regulation is far less challenging an enterprise for them." But, the judge decided, the wording of section 230 was unambiguous. Broad immunity has some "troubling consequences" but courts must ultimately do what is says — at least "until Congress chooses to revise the settled law in this area".

That is exactly what Congress should do.

Struan Robertson is an IT lawyer at Pinsent Masons and the editor of Out-Law.com