Usually a tool of last resort, back-to-work legislation could be used to end labour unrest at Canadian Pacific Railway, where 4,800 engineers, conductors and rail traffic controllers went on strike May 23.

Federal Labour Minister Lisa Raitt says she's putting legislation on the order paper in the House of Commons to send Canadian Pacific Railway's striking employees back to work . "If they cannot conclude their deal, we will have the ability to intervene," Raitt told reporters in Ottawa.

The government has turned to similar legislation to help end several recent strikes and work stoppages. Raitt asked the Canadian Industrial Relations Board to investigate Air Canada's disputes with two of its unions March 8 and then introduced back-to-work legislation March 12 to prevent a work stoppage by pilots, machinists and ground crew at Air Canada. She also introduced back-to-work legislation when customer-service and sales staff at Air Canada walked out in June 2011, but the two sides reached a deal before Ottawa could pass the measure into law.

That same month, the House of Commons passed a bill ordering 48,000 Canada Post employees back to work. The Crown corporation locked out its employees on June 14, 2011, after the union staged 12 days of rotating strikes based on wage and pension issues.

In the face of a long strike or a work stoppage in a key sector of the economy, federal and provincial governments often turn to a back-to-work law to restore important services. 

Unions, meanwhile, see such actions as undermining their collective bargaining rights.

Back-to-work legislation can be a saviour or subverter — it all depends which side of the fence you are on.

What is back-to-work legislation?

It's a special law passed by the government — federal or provincial — that orders an end to a labour-management dispute. The power to force an end to a strike or lockout was reinforced by the Supreme Court in 1987, after the Alberta government asked if unions had a constitutionally protected right to strike. The court said they did not.

What does it do?

Back-to-work legislation ends a strike or lockout by either imposing a binding arbitration process on the two parties of a labour dispute or a new contract without negotiation.

Under arbitration, the union and the employer submit what they are willing to accept a government-appointed arbitrator and the arbitrator reaches a compromise position that both parties must legally accept.

Imposing a contract often occurs when the employees are civil servants, and allows the government to decide the terms of a new collective agreement.

That was the case in February 2010, when Quebec forced 1,500 striking government lawyers back to work with a five-year contract.

When is it used?

Back-to-work legislation is generally used to end a strike — or lockout — in an industry that the government decides is essential to the operating of the economy. It can also be used to end an illegal strike, either by a group that is deemed essential and is therefore prevented by law from going on strike, or workers who have gone out in violation of an existing contract.

Typically, back-to-work legislation is imposed only after some time has passed, further efforts at reaching a settlement have failed, there is considerable public pressure to end the dispute or the service provided by striking workers is deemed essential to the economy or public safety. On some occasions, it has been introduced as a pressure tactic to get negotiations to move faster.

When was back-to-work legislation first used?

On Aug. 22, 1950, Canada's railway unions launched a nationwide strike, shutting down the rail system from coast to coast. At the time, the country depended on the railways to ship everything from food to clothing across the country. Without the freight trains, there were fears that factories would be unable to ship their goods to market and store shelves could go empty.

As well, the railway workers were branded unpatriotic, because their job action did not support the Korean War effort.

On Aug. 29, Prime Minister Louis Saint-Laurent introduced Bill-1, the Maintenance of Railway Operation Act. It ordered an end to the strike and imposed a process for settling the dispute between the workers and the rail companies.

The legislation passed second and third reading, was approved by the Senate and given royal assent the next day. Within days, the railway workers were back on the job.

A byproduct of the strike was the boost it gave to Canada's fledgling trucking industry.

How often is it used?

Since 1950, the federal government has passed back-to-work legislation 33 times, usually to end strikes by railway workers, grain handlers and port workers. It has used back-to-work legislation to end several postal strikes, as well as a 1977 strike by air traffic controllers.

The last time the federal government successfully used the tool was in June 2011, when the House of Commons passed a bill forcing 48,000 Canada Post employees back to work. The legislation, which passed by a vote of 158-113, imposed a four-year contract and certain wage increases on the workers, and went into effect 24 hours later.

In 2007, the government used it to end a strike by 2,800 drivers, yardmasters and trainmen and yardmen at Canadian National Railway Company. In February of that year, striking CN workers reached a tentative agreement with management. However, by April, strike action resumed when United Transit Union workers overwhelmingly rejected the agreement in a ratification vote. The federal government then revived Bill C-61, back-to-work legislation it had introduced in February, and quickly passed it, which forced an end to strike action and imposed an arbitration process on the union and CN management.

On Nov. 30, 2009, the federal government introduced legislation to force striking CN locomotive engineers back to work, but then withdrew the bill when the union and management reached a deal two days later.

Back-to-work legislation has also been used by provincial governments, usually to end disputes in the fields of health care, education and public transit.

The legislation has been used to end transit strikes in Toronto several times, most recently in 2008. The usual pattern in the city — where about 1.5 million people a day depend on public transit — is for the province to legislate an end to a strike within a few days.

It was also used to end a four-month-long transit strike in Vancouver in 2001 — B.C.'s longest transit strike ever. The government had decided that the bargaining process was not working, so it ordered the workers back and appointed a special mediator to resolve the issues.

Are there other options?

Sometimes there are. Governments pondering back-to-work legislation sometimes opt for a sort of "back-to-work lite" — legislation that requires workers to return to their jobs (whether they are on strike or locked out). The bill includes a "cooling-off" period, after which negotiations are given another chance.

That option was considered during Vancouver's transit strike.

Alternatively, governments can ban strikes by passing essential service legislation. Usually, essential services are only those that prevent danger to life, health or safety and disruption of the courts, but in response to economic concerns, the definition has broadened.

Case in point: in March 2011, the Ontario government passed a law designating the TTC as an essential service at Toronto Mayor Rob Ford's request. Supporters of the law argued that the city could not afford another transit strike or lockout, which costs Toronto's economy an estimated $50 million a day.

Essential service designation means that in the event that a negotiation cannot be reached between the union and management, unresolved issues will go to arbitration unless the government imposes a new contract unilaterally.

Critics argue that arbitration often results in expensive settlements, which can be costly for taxpayers, and that removing the right to strike limits unions' bargaining power.

What if the legislation is ignored?

In 1946, unions won the right to collect dues from everyone covered by a contract it negotiated with an employer. But there was another side to that coin — they were also forced to face economic penalties for illegally withdrawing their services.

Under back-to-work legislation, those penalties are spelled out. They usually involve heavy fines against a union, moderate fines against individuals and, sometimes, jail time for ignoring a back-to-work order.

In 2007, Bill C-61, the legislation used to end the strike action by CN workers, called for fines of $50,000 per day against individuals representing the union or employer who defied the law and $1,000 a day for individuals ignoring the back-to-work order. In the event that the union or employer do not respect the conditions of the act, they would be fined up to $100,000. No fines were levied in that dispute.

But in 1978, Jean-Claude Parrot, then leader of the Canadian Union of Postal Workers, was jailed for two months for defying back-to-work legislation.

However, recent back-to-work legislation has opted not to include a prison term among its penalties.

With files from Roland Lindala-Haumont