Sûreté du Québec investigators from the provincial capitol and Chaudières-Appalaches regions arrested Montrealer Daniel Seniw with the help of Montreal police.
He has not been formally charged.
According to Radio-Canada, the comments were posted on a closed Facebook group, "Anglophone Community-Communauté Anglophone du Québec."
"I see an AK-47 walking into the national assembly again and this issue will be passé," Seniw wrote, referring to the Parti Québécois's proposed secular charter.
Claude Roy, who's a member of the Facebook group, told Radio-Canada that ever since he witnessed the Metropolis theatre shooting, he's been monitoring social media for hateful comments.
Roy said that he didn't report Seniw's comment to police, but he did take a screen capture in order to have proof.
"I've been observing that page for several weeks ... and I've seen the radicalism escalate," he told Radio-Canada.
Comment likely referred to 1984 attack
Seniw's comment may have been a reference to a 1984 shooting in the national assembly that left three people dead and 13 wounded.
Just before the shooting, the gunman dropped off a tape at a local radio station explaining his plans to destroy the Parti Québécois.
The Sûreté du Québec said making online threats is a crime, whether or not there is an intention to carry them out.
It said it will investigate any threats or hateful comments.