HELENA, Mont. (CN) – A new federal lawsuit involving a contentious Montana judicial race last year claims an investigation into campaign statements is having a chilling effect on one of the candidate’s ability to defend himself in disciplinary proceedings.

Robert Myers wants a federal judge to strike down Montana’s criminal defamation statute as unconstitutional. He says doing so will not only prevent Myers from being “illegally prosecuted in a criminal proceeding,” but also may encourage other witnesses to come forward without fear that their testimony regarding possible misconduct by Ravalli County District Judge Jeffrey Langton will result in them being charged with criminal defamation.

The newest complaint, filed Thursday, comes almost a year after Myers sued Chief Disciplinary Counsel Shaun R. Thompson over alleged ethics violations included in civil disciplinary complaint against him. Myers said Montana’s disciplinary code, which prohibits attorneys from making false statements about judges, forces judicial candidates to forego exercising their fundamental right to criticize their opponents. A trial before U.S. District Court Judge Donald Molloy is set for Sept. 25 in Helena.

In the newest case, Myers says the court should strike down Montana’s criminal defamation statute as unconstitutional, as it violates his constitutional right to free speech. While the first case was about civil proceedings, in this case it’s a criminal investigation into Myers’ actions that prompted the lawsuit.

“The other federal lawsuit involves a couple of civil complaints filed with the Office of Disciplinary Counsel,” Matthew Monforton, Myer’s attorney, said on Friday. “The lawsuit filed this week is about an investigation that my client committed criminal defamation.

“The government has upped the ante considerably against my client because the previous efforts to silence him over judicial misconduct failed.”

Eric Sell, a spokesman for Montana Attorney General Tim Fox – a defendant in the present case – said Fox hasn’t been served with the lawsuit and couldn’t comment on it. The other defendant, Ravalli County Attorney Bill Fulbright, was out of the office Friday afternoon and couldn’t be reached for comment.

Myers is currently preparing his defense in the civil disciplinary case, but was notified earlier this week by a detective with the Missoula County Sheriff’s Department that Judge Langton had filed a criminal defamation complaint over Myers’ campaign statements. The detective said he was investigating the criminal complaint and interviewing witnesses.

“The ODC’s multiple disciplinary complaints against Myers did not deter him from exposing Judge Langton’s misconduct. So now the government has doubled-down by threatening him with criminal prosecution based upon a patently unconstitutional criminal defamation statute,” Myers says in the lawsuit.

The new criminal investigation will have a chilling effect on witnesses Myers is trying to interview, he says.

“When these witnesses discover that there is an investigation of Myers for criminal defamation … they will become hesitant, to put it charitably, about testifying regarding their own knowledge of Judge Langton’s misconduct,” Myers says in the complaint.

Myers wants the court to “promptly” strike down Montana’s criminal defamation statute as unconstitutional “not only to prevent himself from being illegally prosecuted in a criminal proceeding, but also to encourage other witnesses to come forward without fear that their testimony about Judge Langton’s misconduct will result in them being charged with criminal defamation.”

Myers claims Langton has a history of drug and alcohol abuse, and that he’s also presided over cases in which he was involved. Langton acknowledges that he was cited twice for driving while under the influence in 2005, but that’s “old news” and was re-elected in 2010 and 2016.

Monforton’s office is in Bozeman, Montana.