Management at the smelter has obtained a court injunction limiting the number of unionized employees allowed near the company's aluminum processing plant about 225 kilometres north of Quebec City.
Employees were locked out on New Year's Day and the company was concerned about intimidation against 200 managers tasked with running the plant.
The injunction granted by Quebec Superior Court says only 20 unionized employees will be allowed to man the picket line at a distance of 150 metres from the front door.
Workers have been off the job since early Sunday and neither side is at the bargaining table. The union says the major issue is the company's increasing use of subcontractors to replace workers who are retiring.
The union called the new rules in the injunction "temporary" and a spokesman says they are due in court next Tuesday to argue against the ruling.
In the meantime, union spokesman Dominic Lemieux said the union will find other ways to maintain its visibility.
"We will find other ways to make ourselves heard and mobilize in the region," said Lemieux.
"Our people are united, the climate is very, very good and we have support to last us a long while."
The facility is operating at about one-third of its 438,000-tonne capacity. A company spokesperson confirms that 288 of the 432 reduction cells were shut.
Claudine Gagnon estimated that managers can continue to run at these levels for up to a year if necessary.
Last Friday, about 800 workers from three negotiating units rejected what the company said would be its final offer.
Union officials had a strike mandate before the talks collapsed and had warned that a work stoppage could be imminent.
The company said plans are in place to ensure that aluminium production throughout the region continues to run safely and efficiently.
Management hoped that would limit the impact on its customers.
The Alma facility hosts one of Rio Tinto Alcan's (NYSE:RIO) most important North American aluminum smelters.