Legal to buy, legal to use, and still OWI behind the wheel.

Halloween falls on a Saturday this year, which means a weekend of parties across Metro Detroit, and for a lot of people in 2026 the thing being passed around isn't only a drink. Recreational cannabis has been legal in Michigan since 2018, and that's led to a common assumption that a few hours after a joint or an edible you're fine to drive, because there's no number to be over. Half of that's right. There's no THC limit like the 0.08 limit for alcohol. But the reason is that Michigan never adopted one, not that the law doesn't apply, and a marijuana OWI case gets built from what the officer saw and what the testing shows instead.

Is it illegal to drive high in Michigan if weed is legal?

Yes. The Michigan Regulation and Taxation of Marihuana Act, the 2018 law that legalized adult use, says it doesn't authorize operating a motor vehicle while under the influence of marijuana, and it doesn't authorize consuming marijuana while driving or smoking it in the passenger area of a car on a public road. Driving while impaired is handled by the Vehicle Code, which treats cannabis the same way it treats alcohol.

MCL 257.625(1) makes it a crime to drive while under the influence of alcohol, a controlled substance, or another intoxicating substance, and MCL 257.625(3) covers the lesser offense of driving while visibly impaired. Both apply on public roads and in places open to the public, like parking lots. Michigan's appellate courts have said directly that nothing in the marijuana law was meant to override the Vehicle Code.

Is there a legal THC limit for driving in Michigan?

No. The only numeric limits in Michigan's OWI statute are for alcohol, and there's no blood THC level that counts as impaired by definition. When the Legislature looked at setting one, the Impaired Driving Safety Commission reported in 2019, and it recommended against a THC threshold because the science didn't support one. THC levels in blood don't track impairment the way blood alcohol does, and they can stay measurable long after the effects are gone.

That cuts both ways. Without a number, the prosecution has to prove impairment from evidence: how the car was driven, what the officer saw and smelled, how you performed on roadside tests, and the opinion of a drug recognition expert if one was called. A blood result showing THC is part of that case, but on its own it doesn't prove you were impaired when you were driving, which is often where these cases are actually decided.

What is Michigan's zero tolerance rule for marijuana?

MCL 257.625(8) makes it a crime to drive with any amount of a Schedule 1 controlled substance in your body, and marijuana is still on Michigan's Schedule 1. Read literally, that would make any trace of THC a crime. In People v Koon, decided in 2013, the Michigan Supreme Court held that the medical marijuana law overrides the zero tolerance rule for registered patients, so a patient with THC in their system can only be convicted if they were actually under the influence. Earlier, the Court had also held that the inactive metabolite left behind after use isn't a Schedule 1 substance at all.

For adults 21 and over using under the recreational law, the question isn't settled. The Michigan Judicial Institute's benchbook, which judges use, says it's unclear whether zero tolerance charges will be pursued against adult users and whether the Koon reasoning will extend to them. For drivers under 21, the Court of Appeals held in 2021 that the recreational law doesn't protect them from 625(8), so any amount is enough.

How do police test for marijuana impairment?

Mostly through observation and a blood draw, because there's no reliable breath test for THC. If an officer suspects drug impairment, a specially trained drug recognition expert may run a 12 step evaluation at the station. That testimony isn't automatically accepted in court. In People v Bowden in 2022, the Court of Appeals found the prosecution hadn't shown the drug recognition protocol reliably measures marijuana impairment, which means the method can be challenged.

Roadside saliva testing exists in Michigan only in a narrow form. Under current law, only a certified drug recognition expert in a county taking part in the state's roadside testing pilot program can require an oral fluid test, and refusing it is a civil infraction. Refusing the preliminary breath test is also a civil infraction. Refusing the chemical test after an arrest is different. It triggers a one year license suspension under the implied consent law, and the officer can still get a warrant for your blood, which we explain in our piece on the 14 day deadline after a refusal.

What are the penalties for a first marijuana OWI?

The same as a first alcohol OWI. A conviction under 625(1) or the zero tolerance rule carries up to 93 days in jail, a fine of $100 to $500, up to 360 hours of community service, and six points. Your license is suspended for 180 days, with no driving at all for the first 30 days and a restricted license possible after that.

A drug based impaired driving conviction under 625(3) is the lesser offense but has one difference from its alcohol version. It carries four points, up to 93 days in jail or a fine of up to $300, and a 180 day suspension instead of 90 days, though a restricted license is possible for all or part of it. Our walkthrough of first offense OWI penalties covers the rest of the consequences, and second and third offenses step up sharply from there.

What are the rules for having cannabis in your car?

Don't use it in the car, and keep it put away. Smoking or consuming marijuana in a vehicle on a public road isn't authorized by the recreational law, and doing it gives an officer the observation a marijuana OWI case starts with. An older Michigan statute, MCL 750.474, requires marijuana in a vehicle to be in a case in the trunk, or not readily accessible if there's no trunk, and makes a violation a 93 day misdemeanor. Courts have held it doesn't apply to compliant medical patients, and how it fits with the recreational law's transport provisions hasn't been settled, so the safest practice is a sealed package in the trunk.

For drivers under 21, possession is a civil infraction rather than a crime, but that protection doesn't extend to driving with cannabis in your system. If you're stopped this Halloween weekend, be polite, don't answer questions about when you last used, and call before you decide anything else. Our criminal defense team handles marijuana OWI cases in district courts across Wayne County and Metro Detroit. Cannabis is legal to buy and legal to use, but behind the wheel the old rules still apply, and the case is usually won or lost on the evidence of impairment.

Quick answers

What is the legal limit for THC while driving in Michigan?

There isn't one. Michigan has no per se THC limit for drivers. Prosecutors have to prove impairment through driving behavior, officer observations, drug recognition evaluations, and blood testing.

Can you get an OWI for marijuana in Michigan?

Yes. Michigan's OWI law covers controlled substances, and the recreational marijuana law says it doesn't authorize driving under the influence. A first offense carries the same penalties as an alcohol OWI.

Can you refuse a saliva test for marijuana in Michigan?

Roadside oral fluid tests can only be required by a certified drug recognition expert in a county taking part in the state's pilot program, and refusing is a civil infraction. Refusing a chemical test after arrest triggers a one year license suspension.

Can I have marijuana in my car in Michigan?

You can transport it, but you can't smoke or consume it in a vehicle on a public road. An older statute requires it to be cased in the trunk, so the safest practice is a sealed package in the trunk.

Related reading

• Michigan OWI Penalties for a First Offense
• What Happens After an OWI Arrest in Michigan?
• Refusing a Chemical Test: The 14 Day Deadline
• Criminal Defense at D.C. Law