In an email, a spokeswoman for United to Protect Democracy said the group is “reviewing the motions” and will respond “in due course.”

“But we are confident in our claims,” the statement said. “We stand by the strength of the suit and by the courage of the plaintiffs to stand up for their legal rights.”

SLAPP is the acronym for “strategic lawsuits against public participation,” and several states have enacted anti-SLAPP laws to protect against the chilling effect the threat of litigation can have on free speech. To succeed on an anti-SLAPP motion, defendants must show the lawsuit is based on their speech about public issues. The burden then shifts to plaintiffs to show they have a viable case.

The lawsuit against Stone notes that he said in an interview last year he had “back channel” communications with WikiLeaks founder Julian Assange. Stone also said he engaged in conversations on Twitter with a hacker known as Guccifer 2.0, who claimed credit for the DNC hack. Stone later released screenshots of the messages.

In the motion, Stone claims the plaintiffs are using his protected, public speech to bring frivolous litigation.

“Plaintiffs have been affected by a storyline perpetuated by a constant barrage of media and politicians that do not want the truth to be known, they want their narrative to be true,” the motion said. “This is a conclusion searching for evidence, not evidence leading to a conclusion.”

Still, it’s unlikely an anti-SLAPP motion can succeed, because the U.S. Court of Appeals for the D.C. Circuit held in 2015 that the anti-SLAPP statute cannot be used in federal court. Stone’s lawyers argued it can because it’s pleading requirements are consistent with the Federal Rules of Civil Procedure. There’s a circuit split on the issue, as both the Ninth and First Circuits have allowed such motions to proceed in federal settings.

The case is before U.S. District Judge Ellen Huvelle. Under the current briefing schedule, the plaintiffs’ response is due in late October.