Canada Post says protesters blocking mail from flowing in and out of one of the country's busiest postal hubs are violating a court order.

Most of the protesters who rallied outside a facility in Mississauga Saturday were members of the Canadian Union of Public Employees, acting in solidarity with postal workers who were legislated back to work a week ago.

The back-to-work legislation was passed following about five weeks of rotating strikes by members of the Canadian Union of Postal Workers.

CUPW says 19 protests are scheduled at facilities across the country, allowing workers to enter, but not letting mail out of the plants.