Turns out that back in 2009 the self-described political performance group "Yes Men" held a faux press conference in which they posed as representatives of the Chamber of Commerce to announce that the Chamber was changing its position on climate change. In the short time between the faux press conference and the Chamber's intervention and Yes Men's "this was an elaborate hoax" press release, at least a few one news outlets covered the prank as real (even though the name of the Chamber's president was misspelled and a follow-up call to the Chamber would have revealed the truth).
The Chamber didn't get the joke. And so they did something that in general they aren't known to be in favor of. They sued, alleging commercial identity theft by misappropriation of the business group’s trademarks.
Fast forward about four years, to today. WSJ Law Blog reports that the Chamber is backing off the lawsuit.