The landscape of search and seizure rights is fundamentally changing in states with legal cannabis, and the shift is a massive win for civil liberties. For decades, the distinct smell of marijuana was a “get out of warrant free” card for law enforcement, automatically giving police probable cause to search a vehicle.

But now, state Supreme Courts are pushing back, issuing landmark rulings that align police procedure with the reality of legalized cannabis. The message is clear: The smell of a legal substance, by itself, is no longer probable cause for a warrantless vehicle search.

The Landmark Ruling: People v. Armstrong (Michigan)

The most recent and influential example comes from the Michigan Supreme Court in the case of People v. Armstrong. The court decisively ruled that in a state where marijuana use and possession are generally lawful for adults, the odor of cannabis, standing alone, is not enough to justify the warrantless search of a vehicle.

Why is this so significant?

1. Challenging the “Automobile Exception”: Police often rely on the “automobile exception” to the Fourth Amendment, which allows for a warrantless search if there is probable cause to believe the vehicle contains contraband or evidence of a crime. By ruling that the smell of marijuana alone no longer establishes probable cause, the court has essentially forced police to look for “something more.”
2. Protecting Privacy Rights: The decision recognizes that a lawful smell (a small, legal amount of cannabis) cannot justify an unlawful search. It restores a critical layer of privacy for drivers, ensuring that they are not subject to invasive searches based on a simple, often innocent, odor.
3. A Domino Effect: Michigan is not alone. Jurisdictions like Colorado, Vermont, and even Florida appellate courts have issued similar rulings, recognizing that legalization makes the old “plain smell doctrine” obsolete. These rulings create a legal trend that other states with legalized cannabis are likely to follow.

What Does “Something More” Mean?

The Armstrong ruling clarified that while the smell of marijuana is no longer sufficient on its own, it remains one factor in the “totality of the circumstances” analysis for probable cause.

For police to conduct a legal, warrantless search of a vehicle, the odor must be combined with additional evidence that suggests criminal activity. This “something more” might include:

• Observable impairment of the driver (signs of a potential DUI/DWI).
• Visible smoke or active consumption in a prohibited public place.
• Contraband or paraphernalia in plain view.
• Admission of possessing an illegal quantity or other corroborating admissions.

Your Rights on the Road: Defense Strategies for DUI/DWI and Drug Charges

For drivers, particularly those in states with legalized cannabis, this change in search and seizure law is vital. The legality of the stop and search is often the first, and most crucial, line of defense in a DUI/DWI or drug possession case.

Here’s how this new legal landscape impacts a defense strategy:

• Challenging the Stop: If you were pulled over for a minor infraction, and the subsequent search that found cannabis or paraphernalia was based solely on the odor, your attorney can file a Motion to Suppress Evidence. If the court agrees the search was unconstitutional under the Armstrong standard, the illegally obtained evidence (the drugs, the gun, etc.) must be thrown out, often leading to the dismissal of charges.
• DUI/DWI Defense: In a case involving an alleged Operating While Intoxicated (OWI) or Driving Under the Influence (DUI) of cannabis, a skilled attorney will scrutinize the officer’s justification for the stop and all subsequent steps. If the only initial factor was an odor, but there were no reliable signs of impairment, the entire arrest and any evidence gathered afterward (like Field Sobriety Tests) could be challenged as the result of an unlawful seizure.

The core takeaway is empowerment: Citizens in legalized states are now better protected against unreasonable searches. Law enforcement must now rely on objective, particularized evidence of a crime, rather than a subjective odor that could stem from perfectly legal behavior.

If you have been charged with a crime where the evidence was found after a vehicle search based on the smell of marijuana, it is critical to consult with an attorney immediately. Your Fourth Amendment rights may have been violated, and a successful defense starts with challenging the constitutionality of the search and seizure.

Sources

• Case: People of the State of Michigan v. Jeffery Scott Armstrong
• Citation (Docket No.): Docket No. 165233
• Court/Date: Supreme Court of Michigan, Decided April 2, 2025
• Key Law: Michigan Regulation and Taxation of Marihuana Act (MRTMA) (MCL 333.27951 et seq.), which is the underlying law that superseded the prior “plain smell” rule.