The 10-day-long blockade at General Motors of Canada's Oshawa, Ont., headquarters by members of the Canadian Auto Workers union must end by Monday morning, a judge ruled Friday.

Barry Arseneault directs traffic around a roadblock the Canadian Auto Workers set up at the General Motors head office in Oshawa, Ont. (J.P. Moczulski/Canadian Press)But in his decision, Ontario Superior Court Judge David Salmers also chastised the auto giant, saying it acted deceitfully in announcing the closure of a truck plant in Oshawa by the end of 2009 just three weeks after reaching a collective bargaining agreement with the CAW.

Salmers said the union had until 7 a.m. Monday to vacate the area in front of GM Canada's headquarters.

CAW members began protesting in front of the building on June 4, the day after the company announced it was closing the truck plant, putting 2,600 people out of work.

GM filed the injunction request Thursday, arguing the protest is keeping 900 people away from work and hampering day-to-day operations.

Sean Dewart, lead counsel for the CAW, told CBCNews.ca on Friday the union was "extremely pleased" with the ruling.

"General Motors has engaged in deceitful business practices and has asked for the court's assistance when it has very dirty hands," Dewart said.

He said the judge agreed that "the lawful and peaceful protest had been caused by General Motors' actions."

Chris Buckley, president of CAW Local 222, said his members would abide by the judge's decision to leave on Monday, but would continue their protest over the weekend.

"As of 7 a.m. Monday morning, General Motors can have their building back, and not until," Buckley said Friday after the ruling. "I'm more than satisfied with the judge's decision."

In a statement released on its website following the ruling, GM Canada said it was "pleased that our employees are to regain access to our headquarters building on Monday."

"With this we continue to encourage the CAW to sit down with us to focus on more productive matters and hope this will allow us to discuss potential creative alternatives such as steps to assist impacted employees," the statement said. "We also wish to work together toward potential new product investments for the Oshawa car plant."

On Thursday, the core group of protesters were joined by union members from across the province, creating a rally of about 2,000 people.

GM says higher gas prices and steep declines in truck sales are forcing the plant closure. The automaker says U.S. truck sales in May were down 39 per cent from the same time in 2007.

Last month, GM concluded a collective agreement with the CAW aimed at saving jobs at plants in Ontario.

CAW president Buzz Hargrove said GM is violating the agreement by closing the Oshawa plant, although GM argues that there are clauses in the deal that allow the plant to shut down.

With files from the Canadian Press