The Teamsters union that represents workers at both of Canada's largest freight railroads has filed the lawsuits it promised challenging the orders that forced employees back to work and got the trains moving again, the union announced Friday.

The Teamsters Canada Rail Conference doesn't want to let the precedent stand that the government can block a strike and take away a union's leverage in negotiations. Prime Minister Justin Trudeau's government stepped in to this contract dispute after both Canadian National and CPKC locked out their workers Aug. 22 because of fears about the widespread economic consequences of letting the trains so many businesses rely on remain parked.

"The right to collectively bargain is a constitutional guarantee. Without it, unions lose leverage to negotiate better wages and safer working conditions for all Canadians," the union's President Paul Boucher said Friday. "We are confident that the law is on our side, and that workers will have their voices heard."

CPKC declined to comment Friday on the lawsuits. Canadian National has not commented.

The lawsuits won't stop the trains because the government ordered the union to stay on the job while the arbitration process plays out.

The nearly 10,000 workers the Teamsters represent at both railroads couldn't reach an agreement over a new contract despite negotiations dragging on for nearly a year. The talks deadlocked over the railroads' efforts to switch to an hourly based pay and scheduling system instead of the current mileage-based system. The union worried the changes the railroads proposed would erode their hard-fought protections against fatigue and make their jobs less safe.

The union challenged the labour minister's order that sent the dispute into arbitration, and the Canada Industrial Relations Board decision Saturday that forced them back to work. The labour minister didn't immediately respond to questions about the lawsuits.

Canadian National got moving again the morning of Aug. 23 after being idle for more than a day, but CPKC railroad wasn't able to resume operating its trains until Monday when the order took effect.