A new government proposal in the Australian state of New South Wales could change the rules for motorists who hold a prescription for medicinal cannabis, allowing them to legally get behind the wheel with THC in their system.

Medical cannabis has been legal in Australia for the past decade, but up until now, those with prescriptions could face the same drug driving charges as recreational users. Through a new proposal, individuals who can use medicinal cannabis will be able to drive with up to 50 nanograms per milliliter of THC in their saliva.

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However, if a motorist tests positive for cannabis during a roadside test, they will face an immediate 24-hour driving ban and be compelled to provide another sample for a more detailed laboratory test. If the result of this test comes in below the legal limit, they will be free to get back behind the wheel.

Those who exceed the 50 ng/mL threshold won’t be punished right away. Instead, they could receive two warnings, with charges only following a third infraction. At that point the penalties carry real weight, including an AU$704 ($502) fine and a minimum three-month license suspension.

“These planned reforms represent an important advance in balancing road safety with the needs of medicinal cannabis users, with important safeguards built into the system that protect the integrity of the drug driving enforcement program,” an associate professor from Monash University’s Accident Research Center said. “Being a world first in setting a roadside THC limit, this is a profound change, analogous to the introduction of the blood alcohol limit, and will assist police in keeping the community safe.”

Not everyone supports the idea. Kellie Sloane, the leader of the opposition party, has declared she won’t back the move, ABC News reports.

“The government can put an arbitrary figure on the milligrams of drug in a system, but we do know that every person is affected differently, their impairment is different, and until we have the science on that we shouldn’t be moving forward with these laws,” she said.