Union groups disrupted operations at a Canada Post sorting facility in Mississauga for hours on Saturday, but were told to remove barricades at entrances after the company obtained an injunction.

Representatives said they were rallying in support of postal workers legislated back to work this week.

Canada Post called the barricades "illegal" and said on Saturday it obtained an injunction from the Ontario Superior Court on Friday that prevents "blockading" of its Gateway Facility at 4567 Dixie Rd. The carrier added the injunction is posted at the site.

"The protesters are in violation of the court order," Canada Post said in a tweet. "We will take all appropriate action to address illegal activity impacting the collection and delivery of mail and parcels to Canadians."

Canada Post said the "illegal activity" was being carried out by people who are not its employees and not affiliated with the company. The intention of the protesters, Canada Post claimed, was to block or slow access into and out of its facility.

Members of the Canadian Union of Public Employees in Ontario protest outside a Canada Post sorting facility in Mississauga. They say they support the right of workers to strike. (John Grierson/CBC)

About 100 demonstrators, mostly members of the Canadian Union of Public Employees (CUPE) Ontario, waved placards, chanted, burned wood in barrels and blocked three entrances to the facility.

They said they support the right of the Canadian Union of Postal Workers (CUPW) to strike.

Enforcement officers from the Ontario ministry of the attorney general told the demonstrators at each entrance where barricades had been set up not to disrupt the operations at the facility. The officers read the court order obtained by Canada Post aloud.

Shortly after 4 p.m. ET, CUPE Ontario said in a tweet that its members were "leaving on our own terms" and they removed their barricades.

'Not a necessity for police to step in'

Police were on the scene during the day on Saturday to keep the peace and no one was arrested, according to Const. Sarah Patten, spokesperson for Peel Regional Police.

"We're not going to arrest anyone. It's not a necessity for police to step in," she said. "There have been no public safety concerns."

Patten said police were monitoring the demonstration.

Fred Hahn, president of the Canadian Union of Public Employees Ontario, says working people should be treated fairly. (John Grierson/CBC)

Fred Hahn, president of CUPE Ontario, told CBC Toronto that the union decided to picket the facility because working people deserve to be treated fairly. The facility is the largest and busiest in the country, he added.

Hahn said CUPE Ontario wants Canada Post to know that it supports CUPW in its fight for a collective agreement.

"We're out here to say that: 'Look, it's unfair that their constitutional right to free collective bargaining has been removed," Hahn said on the picket line.

"We're here to say to Canada Post: 'It's not going to be business as usual for you today. You have to actually pay attention to workers' rights and you sit down and bargain a fair collective agreement with the Canadian Union of Postal Workers.' "

Earlier CUPE Ontario claimed in a tweet that it had shut down the facility, saying: "Nobody in, nobody out."

We’ve shut down Canada Post in support of <a href="https://twitter.com/cupw?ref_src=twsrc%5Etfw">@cupw</a>. Nobody in, nobody out. <br><br>Join us at 4567 Dixie in Mississauga. ✊🏽📬 <a href="https://twitter.com/hashtag/negotiatedontlegslate?src=hash&ref_src=twsrc%5Etfw">#negotiatedontlegslate</a> <a href="https://twitter.com/hashtag/peopleforposties?src=hash&ref_src=twsrc%5Etfw">#peopleforposties</a> <a href="https://twitter.com/hashtag/onlab?src=hash&ref_src=twsrc%5Etfw">#onlab</a> <a href="https://twitter.com/hashtag/canlab?src=hash&ref_src=twsrc%5Etfw">#canlab</a> <a href="https://twitter.com/hashtag/cdnpoli?src=hash&ref_src=twsrc%5Etfw">#cdnpoli</a> <a href="https://t.co/N291hMOX0M">pic.twitter.com/N291hMOX0M</a> —@CUPEOntario

Back-to-work legislation was passed on Monday after about five weeks of rotating strikes from CUPW members.

Protest 1 of many across Canada

CUPE said 19 protests are scheduled this weekend at facilities across the country, allowing workers to enter, but not letting mail out of the plants.

Courts in Ontario, Alberta and B.C. have granted injunctions that prohibit anyone from obstructing or interfering with people or vehicles entering or exiting its facilities.

According to CUPW, the union wants better pay and job security, guaranteed hours for its 8,000 rural and suburban carriers, and equality for those workers with the corporation's 42,000 urban employees. It also wants Canada Post to adopt rules that would address workplace injuries.