Nova Scotia RCMP made a rare apology to a woman whose licence was suspended for a week after she failed a roadside test for THC.

The woman, who uses cannabis to treat her multiple sclerosis symptoms, subsequently passed an extensive sobriety test.

As it turns out, the seven-day suspension was a mistake, and the Mounties admitted Thursday that part of what took place during a roadside checkpoint earlier this year shouldn't have happened.

“Typically, the maximum suspension we would be able to issue in that case would be 24 hours,” said Const. Chad Morrison of the Nova Scotia RCMP.

The incident happened after Michelle Gray was pulled over at a routine police checkpoint on Jan. 4 -- more than six hours after taking her dose of medical cannabis.

Gray underwent the RCMP's roadside saliva test for THC and failed.

She was taken into custody in front of her teenaged son, her car was impounded, and her driver's licence immediately suspended for seven days -- all powers given to police by Nova Scotia's Motor Vehicle Act.

But later that same night, she underwent the RCMP’s more extensive sobriety test and passed. That meant she would face no criminal charges for impaired driving.

Gray has accepted the RCMP’s apology and doesn't blame police for enforcing laws she says are flawed.

“If you’re comparing cannabis to alcohol, that's like comparing fish to apples, they are completely totally different things,” Gray said.

She's consulting her lawyers on whether the admission changes the scope of her challenge to the laws around impaired driving and cannabis use.

“We discourage the consumption of cannabis and a decision of an individual to drive, whether it's medicinal or not,” said Mark Furey, Nova Scotia’s justice minister and attorney general.

Furey says the Registry of Motor Vehicles has removed the suspension from Gray's driving record.

But when it comes to any legal challenge to the provincial law, Furey doesn’t seem concerned.

“I'm confident in the legislation around administrative suspensions,” Furey said. “This exists across the country in various models and forms and to this point has been upheld.”

But constitutional law expert Wayne MacKay says there could be a case here, considering these legal waters haven't been tested in Canada before.

“I think there is some possibility of a successful challenge, because unlike the alcohol breathalyzer, this has not been tested in court very much,” said MacKay, professor emeritus at Dalhousie University's Schulich School of Law.

For now, Gray and her lawyers are contemplating their next move in a case that has now garnered attention across the country.

Gray says she has been hearing from people across Canada -- and even from people in the United States -- who are supporting her in her bid to challenge Canada's cannabis laws.

There's even a movement to set up a crowdfunding campaign to help her pay any legal bills.

With files from CTV Atlantic’s Heidi Petracek.