By suing the Yes Men over a prank, the Chamber of Commerce certainly isn't doing anything to change its reputation as a greedy and humorless bunch of suits that puts corporations ahead of the little guy. But could the joke be on the Yes Men by the time this is over?

A quick recap: Last week, the Yes Men, a group of political pranksters working with the activist group Avaaz, set up a mock website that looked like the Chamber's, and held a mock press conference where they announced that the Chamber was shifting its opposition to serious efforts to address global warming. The stunt fooled Reuters and other outlets, who reported the position change, before issuing corrections. In response, the Chamber first tried to have the mock site taken down, then sued the Yes Men for trademark infringement, charging that the prank was "nothing less than commercial identity theft masquerading as social activism."

There's something about the powerful Chamber -- which will meet with President Obama tomorrow, and enjoys the backing of hundreds of thousand of American businesses -- filing legal proceedings against a scrappy group of pranksters that calls to mind a man using a sledgehammer to remove a speck of dust from his eye.

"We've finally made it," Andy Bichlbaum, one of the Yes Men, said in a statement posted on the group's website this afternoon. "We're officially part of the the Extreme Left-Wing Agenda." He added: "It's shameful that the Chamber has decided to lash out at a public interest group like ours for trying to push back and call attention to the Chamber's outrageous positions."

And some critics have charged that this is exactly the kind of frivolous lawsuit that the Chamber has decried in other contexts.

But that doesn't mean the Yes Men are in the clear. At its heart, the Chamber's lawsuit charges "misappropriation of our valuable intellectual property" -- primarily referring to the creation of the fake website -- and argues that this was done for a commercial purpose: to promote the new Yes Men movie, The Yes Men Fix The World. The complaint notes that the Yes Men used the publicity from the stunt to do TV interviews at which they told viewers to see their film.

And one trademark infringement expert we spoke to said they may have a decent case. "This is not a frivolous lawsuit at all," Richard Arrett, a veteran intellectual property lawyer told TPMmuckraker. "If I was the defendant, I'd be worried."

Arrett said that the defense that the site was a parody might not fly, because, unlike true parody, its purpose, at least for a time, was to deceive people into actually thinking that it was associated with the Chamber -- and it succeeded in fooling the press. Nor would "fair use" be likely to hold much water, said Arrett, because the hoax wasn't an example of "scholarly criticism" or any of the other related areas for which the fair use defense was created.

Indeed, said Arrett, the use of the Chamber's seal could even be seen as potentially criminal trademark counterfeiting.

But Corynne McSherry, a lawyer with the Electronic Freedom Foundation, a nonprofit digital rights group that's defending the Yes Men, called this "a pretty straightforward case," that concerns "the use of trademark claims to shut down political speech."

"There's a long tradition in our case law of not allowing trademark claims to silence political criticism," McSherry told TPMmuckraker. "And it's hard to come up with more obvious political criticism than this one."

McSherry pointed out that the prank had succeeded in what she said was its prime goal -- provoking a vibrant public debate about the Chamber's political positions. "This is why we protect free speech," she said.

Despite the Yes Men's history of similar pranks against corporations, it has never before gone to court as a result, the group told Mother Jones.