You should not operate a motor vehicle under the influence of anything. It’s not safe, it’s an unnecessary risk and it selfishly imposes risk from your behavior on other people who had no choice in the matter. At the same time, it’s hard to make an argument for behavior that is not harmful or quantifiably risky enough to be penalized.

Such is the conundrum when it comes to issuing cannabis DUIs. Testing for THC levels in a way similar to how blood-alcohol breathalyzers measure intoxication has proved fruitless, if not impossible. THC is fat-soluble, alcohol is water-soluble. THC metabolites stay in the body long after THC has stopped dancing on the brain.

And such is the reasoning behind the recommendation emerging from a two-year review of how to address roadside “marijuana DUI” testing in Michigan: Don’t do it — or at least, don’t do like you do with alcohol.

According to the Lansing State Journal, a two-year review from the state’s Impaired Driving Commission has recommended to Gov. Gretchen Whitmer and the state legislature that Michigan set “no limit” for how much THC a driver can have in their blood.

Instead, if the recommendations from the expert panel are adopted by lawmakers and obeyed by law enforcement, police would be able to enforce DUI laws in a more old-fashioned way: by observing driving patterns and giving drivers a roadside sobriety test. In fact, this is a thing police are already doing in other states, successfully.

Aiming for Accuracy

According to experts, the level of THC metabolites in a person’s blood is simply not related to their level of impairment. It’s a number that means something else. And arbitrary THC limits set in other states are wholly unscientific.

Thus, “the only reasonable way to do this right now is to demonstrate that people are impaired” through roadside sobriety tests and observing erratic driving, said Norbert Kaminski, professor of pharmacology and toxicology at Michigan State University, in an interview with the Lansing State Journal.

Standard field sobriety tests include following the movement of a light or an officer’s finger with your eyes, walking a line heel-to-toe for nine steps and returning, and holding one leg up six inches in the air for 30 seconds. According to recent research, these tests work as an accurate measure of sobriety — or lack thereof.

The recommendation comes a few months after Michigan voters legalized recreational cannabis. Medical cannabis has been legal in the state since 2008.

Complaints from police about roadside safety and apocalyptic visions of stoned drivers reducing the morning commute to a game of bumper cars set to an Afroman soundtrack are, by now, a predictable verse in the rhythm of the cannabis legalization debate. Some states have tried to ameliorate these concerns by treating cannabis like alcohol — just like the legalization line would have us do — and have determined that a certain level of cannabis metabolites in the blood determines intoxication.

But this “solution” has just caused more confusion. In both Washington and Colorado, that threshold is 5 nanograms per milliliter of blood. But, as state officials have admitted, that number is arbitrary and “not backed by scientific theories.” This has caused a level of chaos… But not on the roads. In courtrooms, judges and juries have been increasingly unconvinced by police assertions of marijuana-induced impairment.

At the same time, law enforcement has proven perfectly able to arrest and prosecute drug-impaired driving cases absent an ironclad, quantified level of intoxication and instead based on driver behavior.

If Michigan lawmakers listen to the experts, they’ll have to pass a law that does not include a limit for the amount of cannabis drivers are allowed in their bloodstream while on the road. Current state law is zero-tolerance for any level of THC in the body for a driver, according to the State Journal — But the chance that such a case would hold up in court is even slimmer now, given the state panel’s finding that such a threshold makes absolutely no sense.

TELL US, how do you know when you’re too high to drive?