Last verified: March 2026

How Michigan's Cannabis DUI Law Works

Michigan's cannabis DUI law under MCL 257.625 uses a zero-tolerance per se standard for recreational cannabis users. This means that any detectable amount of THC in your blood — specifically 1 nanogram per milliliter (ng/mL) or more — is sufficient for a DUI conviction, regardless of whether you are actually impaired.

This is one of the strictest cannabis DUI standards in any legal state. Since THC can remain detectable in blood for days or even weeks after use (especially for regular consumers), a person who consumed cannabis days ago and is driving perfectly fine can technically be guilty of DUI under Michigan law.

A person, whether licensed or not, shall not operate a vehicle upon a highway or other place open to the general public or generally accessible to motor vehicles if the person has in his or her body any amount of a controlled substance listed in schedule 1.

MCL 257.625(8) — Operating Under the Influence

The Medical Patient Exemption: People v. Koon (2013)

The Michigan Supreme Court's 2013 decision in People v. Koon created a critical exemption for medical marijuana patients. The court ruled that registered medical patients cannot be convicted under the zero-tolerance per se standard simply for having THC in their system.

For medical patients, the prosecution must prove actual impairment — that the patient's ability to drive was diminished at the time of operation. This is a dramatically higher burden of proof than the per se standard applied to recreational users.

This exemption is one of the most practical reasons to maintain a medical card in Michigan, especially for daily cannabis users who always have detectable THC levels.

People v. Armstrong (April 2025): Marijuana Smell Is No Longer Probable Cause

In April 2025, the Michigan courts issued another landmark ruling in People v. Armstrong: the smell of marijuana alone is no longer sufficient probable cause for a vehicle search.

Before this ruling, the odor of cannabis gave police automatic justification to search a vehicle and its occupants. Since cannabis is now legal, the court recognized that the smell of marijuana is no more indicative of criminal activity than the smell of alcohol. Officers now need additional evidence of criminal behavior beyond just the smell to conduct a search.

DUI Penalty Chart

First Offense

Subsequent Offenses

Repeat DUI offenses carry escalating penalties including longer jail or prison time, higher fines, longer license suspensions or revocations, and mandatory substance abuse treatment. A third offense within a specified period becomes a felony.

The Zero-Tolerance Problem

Michigan's zero-tolerance standard is widely criticized by cannabis advocates and some legal scholars because of the disconnect between THC detection and actual impairment:

• THC stays in blood much longer than impairment lasts. A person who smoked on Friday evening can still have detectable THC on Monday morning — long after any impairment has worn off.
• Regular users always have detectable THC. Anyone who uses cannabis several times per week will almost certainly test above 1 ng/mL at any given time, even when completely sober.
• The standard effectively makes regular cannabis users permanently DUI-eligible regardless of whether they are impaired.

This is precisely why the People v. Koon exemption is so important for medical patients — and why maintaining a medical card provides meaningful legal protection for daily users.

Open Container Rules

Cannabis in a vehicle must be transported in a sealed, closed container. Best practices:

• Keep cannabis in its original sealed dispensary packaging
• Store it in the trunk or a locked compartment
• Do not store it in the glove box, center console, or anywhere accessible to the driver or passengers

An open cannabis container or recently used product accessible to the driver can result in additional charges or support a DUI investigation.

Practical Tips for Cannabis Users

• Do not drive after consuming. Regardless of the legal standard, impaired driving is dangerous. Wait at least 4 hours after smoking/vaping and 6–8 hours after edibles.
• Consider getting a medical card if you use cannabis regularly. The Koon exemption from the zero-tolerance standard is one of the most valuable practical benefits of a Michigan medical card.
• Store cannabis properly. Keep it in a sealed container in the trunk when driving.
• Know your rights after Armstrong. The smell of cannabis alone does not give police probable cause to search your vehicle. But remain polite and cooperative — other evidence of impairment can still justify a search.
• Use rideshare or a designated driver. Uber and Lyft are widely available in Michigan metro areas.

For more on how cannabis affects driving ability, see Driving & Impairment on TryCannabis.org.