The Hiram Maxim Historical Society filed its suit against the Million Mom March, claiming that spokeswoman Cathie Whittenburg of its Southern Maine chapter made false statements that harmed the society.
At issue are comments attributed to Whittenburg after she received an obscenity-laced hate message via e-mail in response to news reports that she planned to protest the society's machine gun shoot last July.
The society's lawyer, Walter F. McKee, said Tuesday that his client is a law-abiding organization that Whittenburg "essentially called a bunch of terrorists."
Whittenburg said the allegations were false.
"All I can say is that I am flabbergasted and dumbfounded and I am not prepared to talk to the press at this time," she said.
A story July 21 in the Bangor Daily News said Whittenburg had planned to protest the machine gun shoot, but decided not to after receiving the e-mail message.
The story said that "the message was not a threat against her life, she said, but it was serious enough to have local Million Moms change their plans about protesting in Dover-Foxcroft. The hate mail's sender is connected with the machine gun event, the e-mail said."
The same newspaper article paraphrased the machine-gun society's president as saying that "whoever sent the message was acting on his own, not with the authority of the HMHS."
The lawsuit, filed last week in Kennebec County Superior Court, said the society has been harmed by Whittenburg's statements that were made "either negligently or with the knowledge of their falsity or in reckless disregard of the truth."
McKee said he wants to see the e-mail, which he said was not sent by anyone associated with his client.
"We didn't do this," he said. "We want people to know that."
He said the lawsuit is not an effort to silence opponents. "This suit shouldn't cause a chilling effect, because if people are going to speak the truth, they aren't going to be sued."
The Million Mom March has faced other challenges in other states.
The Second Amendment Foundation, a Bellevue, Washington-based organization focused on the right to privately own and possess firearms, asked the attorney general of California to investigate why the Million Mom March received free office space at San Francisco General Hospital through the Trauma Foundation.
Nancy Hwa, a spokeswoman for the Brady Campaign and the Brady Center to Prevent Gun Violence, said she was not aware of the Maine lawsuit, but that "it wouldn't be the first time that somebody from our side has been threatened. We get threatening mail all the time."
The Hiram Maxim Historical Society is named after the Sangerville, Maine, native who invented the machine gun in 1883.