Canadian postal workers vowed civil disobedience as they went back to work Tuesday after the government ended a strike over rising workplace injuries in the booming e-commerce sector.

Online businesses that rely on Canada Post to deliver their wares hailed the move to “salvage the holiday season” but the union representing 50,000 postal workers said “the struggle is not over.”

Canadian Union of Postal Workers president Mike Palecek called the government’s legislation that ended the action “unconstitutional” for trampling workers’ collective bargaining rights.

He vowed “a campaign of mobilizations, demonstrations and non-violent civil disobedience” would follow. Details would be announced in the coming days.