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Reference Guide

Can You Get a DUI for Marijuana in Wisconsin? THC OWI Explained

Yes. Under Wis. Stat. § 346.63(1)(am), delta-9 THC at 1 ng/mL or more in your blood is an OWI, impaired or not. Penalties, the metabolite rule, and defenses.

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Yes, and the rule is stricter than the one for alcohol

Wisconsin does not have a “legal limit” for THC the way it has .08 for alcohol. It has 1 nanogram per milliliter of active delta-9-THC, close enough to zero that a single evening’s use can cross it. Under § 346.63(1)(am), a person may not drive or operate a motor vehicle with a detectable amount of a restricted controlled substance in his or her blood, and § 340.01(50m) puts delta-9-tetrahydrocannabinol on that list at a concentration of 1 ng/mL or more. The State does not need a bad driving pattern, a failed field sobriety test or any evidence of impairment. It needs a lawful stop, a lawful arrest, and a lab report.

That is why THC OWI cases in Racine and Kenosha counties are won and lost on three things: whether the stop and arrest were lawful, whether the blood was lawfully drawn and correctly analyzed, and what, exactly, the lab found.

The statutes in a Wisconsin marijuana OWI
  • Detectable-amount charge: § 346.63(1)(am), a detectable amount of a restricted controlled substance in the blood; for delta-9-THC the definition sets that at 1 ng/mL.
  • Impairment charge: § 346.63(1)(a), operating while under the influence of an intoxicant, a controlled substance or any drug.
  • What counts: § 340.01(50m), which lists delta-9-THC at 1 ng/mL or more and excludes its precursors and metabolites.
  • Prescription defense: § 346.63(1)(d), a valid prescription for the substance.
  • Penalties: § 346.65, identical tiers to alcohol OWI.
  • Roadside screening, including oral fluid: § 343.303 as amended by 2025 Wisconsin Act 99.
  • Post-arrest chemical test and refusal: § 343.305.
  • Counting priors: § 343.307.

The metabolite rule: the detail that decides cases

THC leaves two footprints in blood. Active delta-9-THC is what the statute prohibits. Its inactive metabolite, 11-nor-9-carboxy-THC, stays detectable for days or weeks after the last use and is what most people mean when they say marijuana “stays in your system.” The Legislature excluded metabolites from the definition in § 340.01(50m), so a lab report showing only carboxy-THC does not prove the detectable-amount offense. The State’s fallback is the impairment charge under § 346.63(1)(a), and that charge requires proof you were actually under the influence, which a normal driving pattern and a clean field-sobriety video can defeat.

Active THC at a low level is a harder case, because the statute means what it says. Those cases turn on the stop and the blood draw.

Where the defense usually is

  1. The stop. A traffic stop must be supported by reasonable suspicion of a violation, and a stop that is extended to investigate drugs without new suspicion is unlawful under Rodriguez v. United States. See can police search my car in Wisconsin.
  2. The arrest. Odor alone, red eyes and an admission of use “yesterday” are a thinner probable-cause picture for a drug arrest than for alcohol, and the roadside swab under § 343.303 is a screening device, not proof.
  3. The blood draw. Blood is taken under the implied-consent law, § 343.305, or a warrant. Consent obtained with an inaccurate warning, a draw outside the statutory framework, or a chain-of-custody gap are each suppression issues.
  4. The lab. Which analyte was found, at what level, with what uncertainty, and whether the Wisconsin State Laboratory of Hygiene’s method and the analyst’s testimony hold up on cross-examination.

Penalties follow the alcohol tiers

A THC OWI is punished under § 346.65 exactly as an alcohol OWI with the same prior record: a first offense is a civil forfeiture with a 6- to 9-month revocation, a second within 10 years is a misdemeanor with mandatory jail, a fourth is a Class H felony, and every one counts as a prior for life from the third offense on. A first offense with a passenger under 16 is criminal from the start. Ignition-interlock requirements do not attach to a drug-only first offense the way they do to a high-alcohol one, but a revocation and an assessment do.

Wisconsin, Illinois and the border

Kenosha County’s I-94 corridor produces a steady volume of THC OWI arrests of Illinois residents who bought cannabis legally an hour south. Legal purchase in Illinois is not a defense in Wisconsin; possession of the product in the car is a separate charge under § 961.41(3g); and the Wisconsin conviction will be reported to Illinois for license purposes. Read the Kenosha court guide and, for the marijuana possession side, marijuana laws and charges.

The dedicated OWI site

This firm runs racineowi.com for OWI defense in Racine, Kenosha and Walworth counties, with offense-tier penalty tables, refusal-hearing deadlines, occupational-license timing and the 2026 ignition-interlock changes under Act 210. For a THC arrest, start there or call (262) 632-5000; the phone is answered 24 hours a day and the case review is free.

Questions people actually ask

Can you get a DUI for marijuana in Wisconsin?
Yes, and Wisconsin's marijuana OWI law is stricter than its alcohol law. Under Wis. Stat. § 346.63(1)(am), it is an offense to drive with a detectable amount of a restricted controlled substance in your blood, and under § 340.01(50m)(e) delta-9-tetrahydrocannabinol counts at a concentration of 1 nanogram per milliliter or more. The State does not have to prove you were impaired. A separate charge under § 346.63(1)(a) covers driving while actually under the influence of THC or any drug. Penalties are the same tiers as an alcohol OWI under § 346.65: a civil forfeiture for a first offense, criminal from the second. Wisconsin calls it OWI, not DUI, but the charge is the same. Cafferty, Scheidegger & Johnson, S.C. defends THC OWI cases in Racine, Kenosha and Walworth counties; the dedicated site is racineowi.com, and the phone is (262) 632-5000.
Is there a legal THC limit for driving in Wisconsin?
No. Unlike the .08 alcohol limit, Wisconsin has a near-zero rule for delta-9 THC under § 346.63(1)(am): a detectable amount is enough, and § 340.01(50m)(e) sets the floor at 1 nanogram per milliliter of blood. There is one important exclusion written into the same definition: it covers delta-9-tetrahydrocannabinol but excludes its precursors and metabolites, so the inactive metabolite carboxy-THC, which stays in the body for days or weeks after use, does not count. The lab report must show active delta-9 THC. Reading the toxicology report correctly is the first thing we do in every THC OWI case.
Can I be charged with OWI for marijuana I used days ago?
Not under the detectable-amount statute if the lab found only the metabolite, or active THC below the 1 ng/mL floor in § 340.01(50m)(e). Active delta-9 THC typically falls below detection within hours for occasional users, but can persist longer in daily users, which is where these cases get contested. If the report shows active THC at a low level, the § 346.63(1)(am) charge is provable regardless of impairment, and the defense turns on the stop, the arrest, and the blood draw. If it shows only carboxy-THC, the (am) charge fails, and the State is left with the (a) impairment charge, which requires proof that you were actually under the influence.
What are the penalties for a THC OWI in Wisconsin?
The same as an alcohol OWI, set by § 346.65(2). A first offense is a civil forfeiture of $150 to $300 plus surcharges, a 6- to 9-month license revocation, and an alcohol and drug assessment. A second offense within 10 years is a criminal misdemeanor with 5 days to 6 months in jail; a third is 45 days to a year; a fourth is a Class H felony. Every conviction is a countable prior under § 343.307 for life from the third offense onward. A THC OWI with a passenger under 16 is charged criminally even as a first offense. Full penalty tables are on racineowi.com.
Can I refuse the roadside saliva test for marijuana in Wisconsin?
The roadside oral-fluid swab authorized by 2025 Wisconsin Act 99 is a preliminary screening device under § 343.303, in the same category as the handheld breath tester. Refusing it is not a refusal under the implied-consent law, § 343.305, and does not by itself trigger the revocation that refusing a post-arrest blood test does. It can, however, be part of the officer's probable-cause picture for an arrest, and after arrest you will be asked for a blood draw under § 343.305, where refusal has serious consequences. Our post on refusing the roadside saliva test in Racine covers the distinction in detail.
Is medical marijuana a defense to OWI in Wisconsin?
Wisconsin has no medical marijuana program, so an out-of-state medical card is not a defense. Section 346.63(1)(d) does provide a defense to the (am) charge if the driver proves a valid prescription for the substance, which reaches FDA-approved prescription THC (dronabinol) but not dispensary cannabis from Illinois or Michigan. Products that are legal in Wisconsin, including hemp-derived Delta-8, can still produce a positive test for delta-9 THC, and legality of the product is not a defense to a detectable-amount charge. Read is weed legal in Wisconsin for where the law stands in 2026.