The Columbia Missourian reports the duo were suspected of recording the film. When staff asked them to leave, they refused, leading to the involvement of local police.
"We thought that they were possibly recording the film, and because of that suspicion and because of problems filmmakers have had in the past doing a similar type thing, we alerted the Columbia police," festival director David Wilson said.
"It's possible they work for one of the people in the film who appears to have a very litigious background.
"This film makes a very strong case that this person has treated other people in very terrible ways."
Farrier tweeted about the disturbance at the screening and thanked those who had gone to see the film. He apologised for the interruption and praised festival staff and police for their efforts.
And if that wasn't dramatic enough, Farrier then revealed he had been served with legal papers relating to Tickled.
Sharing a photo of the moment the papers were served, Farrier told his followers he initially thought the woman who gave them to him was a fan.
When asked on Twitter if the papers related to Tickled, Farrier's co-director Dylan Reeve confirmed they did, adding "We officially have no comment."
According to The Columbia Missourian, Farrier later told the audience at another screening of his film that he was facing legal action.
"I'd love to talk more ... but I can't because I'm already in trouble," he said.
