Can you get an OWI if you're no longer high? What Marijuana Users Need to Know About Wisconsin’s OWI Laws

Minnesota legalized recreational marijuana in 2023. Michigan did so years earlier. As legal cannabis becomes more common across the region, it is worth understanding how Wisconsin OWI laws treat marijuana and driving—whether you are a Wisconsin resident or someone traveling into the state from a place where cannabis is legal.

If you’ve ever wondered about OWI vs DUI, or asked yourself what is an OWI charge, the distinction becomes especially important when marijuana is involved.

Many people understand drunk driving in terms of the familiar 0.08% blood alcohol limit. If the state can prove you were over that limit, you can be convicted of OWI. People intuitively understand that there is a threshold, a line you have to cross before you've broken the law.

Wisconsin's approach to marijuana is completely different. Under Wisconsin Statute § 346.63(1)(am), it is illegal to operate a motor vehicle with a "detectable amount of a restricted controlled substance" in your blood. And under Wisconsin's statutory definition, delta-9-tetrahydrocannabinol (THC) - the active compound in marijuana - is a "restricted controlled substance."

In other words, there is no “legal limit” for THC in Wisconsin; driving with any amount of THC in your blood is a crime. This is not a law about whether you are impaired at the time of driving. It is a law about whether a measurable trace of THC is present in your bloodstream.

This is the part that surprises most people, including people who consider themselves responsible cannabis users. Under Wisconsin's restricted controlled substance law, the state does not have to prove that marijuana affected your driving. It does not have to prove you were impaired by marijuana. It does not have to prove you felt anything at all. The Wisconsin Supreme Court has addressed this directly, and the law is written as what's called a "strict liability" offense: if the substance is present in your blood above the statutory threshold, that is a violation of the law.

This is a sharp contrast to Wisconsin's other OWI provision, which requires proof that you were operating a vehicle while "under the influence" — meaning your ability to drive was compromised. The restricted controlled substance law requires no such showing.

If you consumed cannabis legally in Minnesota or Michigan, waited what felt like a reasonable amount of time, and then drove into Wisconsin, you may still have detectable THC in your blood.

THC is fat-soluble, which means it is stored in body tissue and released gradually over time. Regular cannabis users can have detectable blood THC levels for days after their last use, even when they are experiencing no impairment whatsoever. Occasional users typically clear THC faster, but the window is not as short as many people assume.

There is no breathalyzer equivalent for THC. Law enforcement typically uses a blood draw to establish THC concentration. If you are stopped in Wisconsin and an officer develops probable cause to believe you may have a restricted controlled substance in your system, a blood draw may follow. Wisconsin's implied consent law means that refusing to submit to chemical testing carries its own serious legal consequences, including potential license revocation.

A first-offense violation under the restricted controlled substance provision is a civil violation that carries fines and license revocation. But it also goes on your record and counts as a prior OWI offense for purposes of any future prosecution. A second offense becomes a criminal matter. The stakes escalate quickly, and Wisconsin prosecutors and courts treat these cases seriously.

Wisconsin is surrounded by states where recreational marijuana is legal. It's easy to assume the rules are similar, or that what you do legally across the border won't matter once you get here. That assumption is wrong, and it can cost you your license, your money, and potentially your freedom.

If you have used marijuana, even legally - even days ago - and you are driving in Wisconsin, you may be in violation of state law regardless of how you feel behind the wheel. Wisconsin law does not ask whether you are impaired. It asks whether the substance is there.

Written by Mac Blessen, OWI Defense Attorney at Nelson Defense Group