Last year, the annual Cannabis Day celebration in downtown Vancouver was marred by a police crackdown, resulting in four participants being pepper-sprayed and hauled away to jail.
This year, organizers say a rival group called World Cannabis has "disrupted" the event outside the Vancouver Art Galery.
According to marijuana-legalization activist Dana Larsen, the others are "trying to do a hostile takeover".
"World Cannabis came in at 5 a.m. and set up some speakers," Larsen said in a news release emailed to the Georgia Straight. "We've been putting this one for 21 years now, but today these haters are sabotaging our event and trying to take over."
He alleged that a long-time Cannabis Day organizer, Jeremiah Vandermeer, was assaulted.
Another Vancouver cannabis-legalization activist, Jodie Emery, has claimed over Twitter that a "fringe group" has taken over the event.
Cannabis Day is an annual celebration and trade fair for enthusiasts of hemp and marijuana products.