Business owners and unions are calling on companies to quickly revise their policies regarding marijuana in the workplace.

With cannabis being legalized this week, many people are still uncertain whether or not they will be allowed to use marijuana before or during the work day -- and there are studies showing some managers plan to toke up while on the job.

Many people are worried that more people will use marijuana once it is legalized, although the Conseil du Patronat, Quebec's largest employers' group, says there is no evidence that is likely.

But officials in many industries say it's a good time to update policies to make it explicit that marijuana use on the job is not allowed, and to make it clear that employees who use heavy equipment or vehicles should not use marijuana before coming to work.

"An employee cannot be drunk at work. It's the same thing for cannabis, they cannot be high at work," said Guillaume Houle of the Quebec Construction Association.

"If an entrepreneur finds someone who is using pot on their dinner times [meal breaks] he has to take him aside, talk to him about the risk that he is taking, for taking the drugs during his work hour and send him home for the rest of the day."

Employers cannot implement random drug tests to check for cannabis use.

Current Canadian law and jurisprudence says that random drug testing is a violation of privacy and can only be implemented with employees' consent, or if an employer is able to prove there are sufficient safety concerns.

But it's not easily done.

A court battle is underway in Alberta where Suncor attempted to implement random drug testing in oil fields, but after several hearings at various courts, including the Court of Appeal, the legal fight is not yet over.