The U.S. Chamber of Commerce has sued the pranksters Yes Men for trademark infringement for allegedly creating a fake site stating that the group now supports climate change legislation.

The lawsuit, filed Monday, comes one week after the Yes Men held a fake press conference announcing that the business association had changed its position on environmental legislation. The Yes Men also posted a phony press release on a parody site -- which closely resembles the real site's media center page.

The stunt fooled some real news outlets, including Reuters, which reported that the Chamber of Commerce had changed its stance on climate change legislation. In fact, the Chamber of Commerce's criticism of a pending bill aimed at curbing global warming has led to some recent membership defections by major companies, including Nike and Apple.

The Chamber of Commerce alleges in its lawsuit that the prank was all part of a publicity campaign for the movie "The Yes Men Fix The World," released nationwide last week.

The business group has asked the court to order the Yes Men to take down the site and to ban the pranksters from impersonating Chamber of Commerce representatives. The case is pending in federal district court for the District of Columbia.

The Yes Men declined to comment except to issue the statement: "It's very disappointing, even to us, that the Chamber would take an approach like this to what is very obviously political criticism."

The business group argues that the fake site too closely mimics the real site; the joke site goes so far as to contain links to the genuine site. "Rather than create a parody site that resembles the Chamber's site, the fraudulent pages copy embedded software elements from the Chamber's web site," the business organization alleges. "This ensures that if a visitor 'clicks' any links on the fraudulent pages they are taken to the authentic chamber web site."

Therefore, the Chamber alleges, members of the public "would have no idea that they were visiting a fraudulent site, rather than the Chamber's legitimate site."

By late last week, the Chamber of Commerce revised its own site by adding a banner that warns visitors who arrived from the parody that they had come from a "hoax site."

The Chamber of Commerce also demanded last week that Hurricane Electric Internet Services remove the site on the grounds that it infringed the business group's copyright. Hurricane Electric is one of several Internet access providers used by May First/People Link, a cooperative organization that provides Internet services to around 400 members, including Yes Men.

The Electronic Frontier Foundation wrote to Hurricane Electric on behalf of Yes Men and asked the company to keep the site live, arguing that the parody was protected by fair use principles.

Hurricane Electric nonetheless took down the Yes Men site -- and also briefly took down the sites of hundreds of other May First/People Link organizations. Those other sites were down for around 90 minutes on Thursday night before May First/People Link was able to convince Hurricane Electric to restore service to them. May First/People Link was able to arrange for another ISP to host the Yes Men parody, which was back online by Friday.

Although the stunt seemed to have created some confusion in the media, it's not clear that the lawsuit will get far in court. Trademark infringement requires use in commerce, and there are questions about whether the Yes Men's use of the business group's logo for a parody is a use in commerce.

In addition, trademark law is aimed at preventing consumer confusion, which in this case would appear to mean confusion by the Chamber of Commerce's members, or potential members. And even if the Chamber of Commerce can show some likelihood of confusion among that group, a court would still have to consider whether the Yes Men have a First Amendment right to mock the association.

Cyberlawyer Venkat Balasubramani says that issue isn't clear-cut, adding that it raises the question of how far people can go to poke fun at others, and whether copyright or trademark owners "should be able to use those rights to squelch criticism."

But David Johnson, an expert in digital media law, says that the Yes Men might have gone too far by creating a fake site that looks so much like the real one. "This is a little too good," he says.

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