HALIFAX -- Parallels are being drawn between Nova Scotia's passage of a bill Friday to end a nurses strike and a similar law in Saskatchewan that's the subject of a Supreme Court challenge.

Nova Scotia became the latest province to enact essential services legislation for health-care workers on Friday, joining other parts of the country that have longer experiences with this approach to collective bargaining.

The law in Nova Scotia requires unions and employers throughout the health-care sector to have an essential services agreement in place before a strike or lockout. If such a deal can't be reached, an independent third party decides.

Experts say other provinces have had mixed results with their legislation.

Larry Haiven, a professor of management at Saint Mary's University in Halifax, said laws like the one in Nova Scotia and Saskatchewan are drawing union anger because arbitrators will tend to "err on the side of caution" and set high levels of staffing.

High emergency staffing levels weaken a union's bargaining power, he said, and health workers' grievances build to the point where there's a risk of illegal walkouts or mass resignations.

"The union members get very cynical about the whole thing and they begin to engage in civil disobedience," said Haiven, who has written a series of papers on the topic over the past decade.

Saskatchewan's legislation is being challenged at the Supreme Court of Canada next month, with unions arguing it violates charter rights of association and freedom of expression.

The Nova Scotia Government and General Employees union is looking at its own legal challenge of the bill passed Friday, which shut down a strike by 2,400 nurses in Halifax but applies to as many as 40,000 workers ranging from paramedics to people who work in homes for seniors, youth and people with disabilities.

Union president Joan Jessome said she'll meet with nurses next week to discuss tactics, including a constitutional challenge of the bill.

"They have changed the face of labour relations in this province," Jessome, fighting back tears, said after the bill passed early Friday morning following an all-night session of the legislature.

The dispute in Nova Scotia centred on a call by the nurses for higher staffing levels. They want a collective agreement that includes mandated nurse-to-patient ratios in the interests of patient safety.

The Capital District Health Authority questioned whether patient safety would be improved by mandated ratios and called such a system too inflexible.

Ray Larkin, the lawyer for the union at the centre of the dispute in Nova Scotia, said while cases wind their way through the courts, bargaining in Nova Scotia will get bogged down.

He said a system that requires a deal on essential services before talks on a collective agreement can even begin will create a huge backlog as union local after union local goes to the Nova Scotia Labour Board.

"Collective bargaining in health and community services will be tied up for several years. It's highly questionable whether it's a form of bargaining that's practical," he said.

Debbie Forward, president of the Newfoundland and Labrador Nurses Union, warns that even though the province has had essential services legislation for several decades, it hasn't stopped disruptions.

Under Newfoundland and Labrador's legislation, if health districts can't function with 50 per cent or less of its staff at a given facility, then it has to submit the union's issues to binding arbitration.

Forward said she has concerns about legislation that requires higher emergency staffing levels, saying the employer loses an incentive to settle.

"It appears governments are making it harder and harder on unions," she said.

Labour Minister Kelly Regan said in an email she's confident Nova Scotia's law will be fair.

"When government decided to introduce this bill, we set out to ensure that the health and safety of Nova Scotians is protected at all times, even during a labour dispute," she wrote. "We also wanted to ensure that this government continued to respect the right of workers in this province."

Pat Parenteau, director of policy at Saskatchewan's Ministry of Labour, said the province's essential services bill and amendments planned for later this spring are also designed to create a fair balance between labour rights and public protection.

Like Nova Scotia's bill, the amendments include a provision that says if the number of emergency workers deprives employees of a meaningful right to strike, the labour dispute can go to an arbitrator.

She said she expects labour boards in both provinces will balance the rights of workers against the protection of the public.

Ray Thorpe-Dorward of the Health Employers Association of B.C. said essential services legislation in the province has improved labour relations.

"This approach has led to several rounds of successful bargaining without significant labour disruption," he said in an email.

"In our experience, essential service requirements has resulted in more productive labour relations."