Canadian National Railway Co. lifted its lockout of picketing workers as Canadian lawmakers ordered an end to the labor dispute at the country’s largest railway.

The back-to-work bill, passed by the House of Commons, was endorsed by the Senate and almost immediately received royal assent to make it officially law.

Although the measure gave the sides 24 hours to end the job action, CN invited workers to return immediately. It had locked out workers who staged rotating strikes at a handful of terminals after rejecting a tentative contract deal.

The workers had already said they were ready to return.

The United Transportation Union, which represents the 2,800 Canadian conductors, brakemen and switching crews, denounced Parliament’s intervention in the dispute, saying it did not resolve wage and work-rule issues that sparked the strike.

The union said the government’s action could allow Montreal-headquartered CN to impose work rules strongly opposed by the employees.

The back-to-work bill calls for the appointment of an arbitrator who can decide the terms of the next contract for the workers, picking either a proposal made by the union or one made by the company.

“They (CN) want to break up our bargaining unit in order to weaken the workers’ ability to stop management from pushing older workers out of the door and manipulate work rules and schedules at workers’ expense,” the UTU said in a statement.

The rejected proposal included a three percent wage increase.

A CN spokesman said it was premature to speculate on what might happen with arbitration.

Chief Executive Hunter Harrison has complained that current contracts in Canada do not reflect changes in CN’s operations in recent years or meet the needs of younger workers choosing between the railway and other occupations.

CN’s contracts with train crews in the United States use hourly pay systems, while most of its crews in Canada work under the industry’s traditional mileage-based system. The US crews are not involved in this contract dispute.

Canadian National has said it might try to negotiate regional contracts in Canada, asserting that a bitter split in the UTU’s leadership has made it impossible to reach a national settlement that would win worker approval.

Overshadowing the arbitration is a move by the Teamsters union to take over representation of the 2,800 workers. The Teamsters have asked labor regulators to order a vote. (Reuters)