TORONTO -- As medical marijuana gains traction as a treatment option for a host of conditions including chronic pain and other conditions, Canadian employers could find themselves grappling with a sticky issue.

"Individuals have the right to equal treatment ... without discrimination on the grounds of disability," says Jan Robinson, managing principal at human resources firm Morneau Shepell.

"Medical cannabis now needs to be viewed like every other doctor-prescribed drug."

But although employers have a duty to accommodate workers' medical conditions, experts say that duty must be balanced with the need to keep the workplace safe. That can be challenging, especially if employees perform duties such as operating machinery.

"There's no hard or fast rule to this," says Natalie MacDonald, an employment lawyer and the co-founder of Rudner MacDonald LLP. "It's got to be determined on a case-by-case basis -- as most things in employment law do."

Experts says the duty to accommodate comes with an important caveat -- it must not result in undue hardship for the employer.

While there is no strict definition of what constitutes undue hardship, MacDonald says the courts will consider a number of factors including how much financial difficulty the company would endure and whether accommodating the employee would compromise workplace safety.

"A small organization that has to incur serious financial hardship as a result of trying to accommodate an employee may cross the test of undue hardship," MacDonald said.

A recent decision issued by the British Columbia Human Rights Tribunal illustrates some of the limits that apply to the employer's responsibility to accommodate workers' needs.

The Tribunal ruled in July that B.C.-based Selkin Logging did not violate John French's human rights by refusing to allow the logging contractor to use marijuana while on the job.

The company, which has a "zero tolerance" policy on marijuana use, had argued that it did not discriminate against French based on his use of cannabis to handle the symptoms of cancer, but rather was concerned about safety.

In addition, French was not authorized by Health Canada to possess medical marijuana, although he claimed he was using the drug to ease cancer-related pain as per his doctors' recommendations, according to court documents.

MacDonald says that if French had proper medical documentation, the outcome of the case may have been different. However, safety concerns still need to be taken into account, she adds.

One alternative way to accommodate a worker's needs would be to provide the worker with a leave of absence until the medical issue is resolved, MacDonald said.

"In some cases, it may be that the employee needs to be provided with alternative forms of work that don't attract any particular safety concerns," MacDonald said.

As cannabis becomes a more popular treatment choice -- Health Canada has estimated there could be nearly half a million users by 2024 -- the issue is likely to start cropping up at workplaces across the country.

"We are starting to recognize that this trend will commence very shortly across Canada," said Robinson, noting that Morneau Shepell has been advising its clients to review their existing drug and alcohol policies to ensure they are adequate.

"If they don't look at their drug policies now, they may have issues in the future," she said.