TORONTO– The Teamsters union, which represents workers at Canada’s two largest railways, said Saturday it will abide by a back-to-work order and send its members back to work. But it will continue to pursue a legal challenge to the order.

“This decision by CIRB sets a dangerous precedent. It sends a message to Corporate Canada that all it takes is for large corporations to cease operations for a few hours, cause short-term economic pain, and the federal government will step in to bust a union,” said Paul Boucher, president of the Teamsters Canada Rail Conference.

“The rights of Canadian workers have been significantly curtailed today,” Boucher added.

THIS IS A BREAKING NEWS UPDATE. Below is the earlier AP story.

The Canadian arbitrator appointed to resolve a messy railway labour dispute in a bid to protect the North American economy has ordered workers at the country’s two largest railways to return to work so both companies can resume operations.

If the union of more than 9,000 engineers, conductors and dispatchers follows through, the order should keep Canadian National trains running and allow the Canadian Pacific Kansas City Ltd. railway company to resume operations.

Both railroads have said they will comply with the Canada Industrial Relations Board’s orders. Canadian National trains resumed running Friday morning, but the Teamsters Canada Rail Conference threatened to strike there starting Monday morning. CPKC workers have been on strike since the lockout began Thursday morning, and the railroad’s trains have been idle.

Union officials have said they will “work within the framework of the law” even as they challenged the constitutionality of the arbitration ruling announced by the government on Thursday afternoon to avoid potentially disastrous consequences for the economy.

Businesses across Canada and the United States said they would soon be in crisis without rail service, as they rely on freight trains to deliver their raw materials and finished products. Without regular deliveries, many businesses could be forced to reduce production or even close.