The Canadian Union of Postal Workers (CUPW) said it was filing the challenge Tuesday in the Ontario Superior Court, arguing the bill is a violation of constitutional rights.
On Nov. 26, Ottawa passed Bill C-89, forcing an end to five weeks of Canada Post’s rotating strikes.
But the union said the bill violated the rights of workers to collective bargaining.
“You cannot legislate labour peace,” Mike Palecek, CUPW president said in a statement. “This law violates our right to free collective bargaining under the Charter of Rights and Freedoms.”
WATCH: Canada Post union supporters protest back-to-work legislation
This isn’t the first time CUPW has taken the government to court.
In 2011, the Conservative government legislated a back-to-work bill after Canada Post locked out CUPW members for two weeks. The postal workers took the action to court and the union won the key legal case when an Ontario court found that legislation was unconstitutional.
The union’s lawyer, Paul Cavalluzzo, said the back-to-work legislation was passed after Canada Post created a “false emergency” over a backlog of parcels at the Crown corporation’s sorting plants.
“The Liberal government’s legislation, just like the previous Conservative’s, unilaterally prohibits any lawful strike,” Cavalluzzo said. “Canada Post created a false emergency, the supposed backlog of parcels, to get the government to intervene with back to work legislation. This legislation was enacted under circumstances that did not justify the interference of constitutional rights.”
Canada Post said yesterday that, while letter mail is moving well, parcel deliveries are sporadic and delivery delays are expected through January as a result of the rotating walkouts that ended Nov. 27.
— With files from the Canadian Press