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Is driving with hemp or THC legal in Wisconsin? OWI rules to know
Gina Lee Castro
Hemp and its many intoxicating products have been legal in Wisconsin for eight years. But driving around with hemp products could still put you in hot water with the law, said Milwaukee attorney Andrew Mishlove.
Hemp looks and smells identical to marijuana, and both come from the Cannabis sativa L plant. But hemp is legal – for now – and marijuana is not.
When hemp users drive with these products in their cars, a police traffic stop can spiral into citations or even jail time, said Mishlove, who specializes in defending people charged with operating while intoxicated.
“It’s a mess,” he said. “Hemp is legal. Wisconsin law hasn’t caught up with that reality at all.”
Here's what we learned about why hemp can still put Wisconsin drivers at risk of an OWI.
Is it legal to drive with hemp in my car in Wisconsin?
Yes, but it’s a risk, Mishlove said.
If police officers catch a whiff of weed from a car or see it in the car, they can easily gain probable cause to make an arrest for possession of a controlled substance or begin an investigation into operating while intoxicated, Mishlove said.
Overall, state law doesn't say much about driving with hemp. Wisconsin doesn’t have an open container law for hemp the way it does for alcohol, Mishlove said. Nor is there a limit on how much hemp an individual can possess, or any laws on how drivers can lawfully transport hemp.
In contrast, in Illinois, where cannabis is legal, the product must be sealed in a child proof container and inaccessible to the driver.
Is it illegal to drive with hemp in my system in Wisconsin?
Yes. Wisconsin law does not allow drivers to have any THC in their blood. Any amount above one nanogram per milliliter is considered evidence of operating while intoxicated.
Although hemp is restricted to trace amounts of THC - the component in cannabis that makes users feel high - some products contain THC in amounts comparable to states where marijuana is legal.
In fact, a recent Milwaukee Journal Sentinel investigation found that many hemp products in Wisconsin contain THC above the federal legal limit, with consumers none the wiser. Some gummies and drinks below the federal legal limit still packed over 10 milligrams of THC per serving.
In addition, some hemp products contain a compound known as delta‑8 THC that is so similar to traditional THC that it appears chemically indistinguishable in blood testing, Mishlove said.
The THC blood test has been criticized by some scientists and lawmakers who say the limits are arbitrary and do not necessarily constitute impaired driving.
How does law enforcement determine impairment?
The Wisconsin State Laboratory of Hygiene conducts blood testing for law enforcement agencies across the state. Kayla Neuman, director of forensic toxicology, said the test cannot determine whether a person is impaired, nor can it show when THC was last consumed. The test only confirms that THC is present in a person’s system.
Neuman said observations from officers and results from roadside impairment tests contribute to evidence of impairment.
Chronic, daily THC users are more likely to have detectable levels of THC in their blood at all times and can exceed the one‑nanogram legal threshold, Neuman said.
But due to Wisconsin's zero-tolerance policy, people can be charged with an OWI even if they are sober, Mishlove said.
“It doesn’t matter whether you are impaired or high on this stuff or not,” he said. “You can’t have it in your system and drive.”
What are the laws in other states around THC and driving?
The Michigan Impaired Driving Safety Commission has said there is no scientifically supported threshold of THC in the body that proves impairment. As a result, Michigan doesn’t have a legal limit for THC. Instead, a series of roadside sobriety tests must prove the driver is impaired.
In some states where marijuana is legal, like Illinois and Colorado, the limit is five nanograms of THC, to account for chronic users.
How can hemp users in Wisconsin steer clear of legal trouble?
If you're a hemp user and plan to drive, try to keep documentation on you.
For example, Milwaukee Police Lt. Matthew Kaltenbrun said showing officers a certificate of analysis – a third-party lab test of the specific hemp product – is good evidence that the product in question is hemp, not marijuana.
Mishlove added that keeping the product's original packaging and receipt of purchase can prove the product was bought legally in Wisconsin.
As for how frequent users can prove they aren't currently impaired by THC, that's a tricky one.
"I advise people to not break the law," Mishlove said. "The law says don't drive with a restricted substance in your system. Don't use those products and drive in Wisconsin."
Gina Castro is a Public Investigator reporter for the Milwaukee Journal Sentinel. She can be reached at gcastro@usatodayco.com.
Saturday, April 4, 2026
Wisconsin police can now test saliva if they suspect drugged driving
Hope Karnopp
A new state law allows police who suspect drugged driving to perform a rapid roadside test of the driver's saliva to check for THC, opioids, meth and more, though police departments don't appear ready to roll it out immediately.
State law already allows police to use breathalyzers to check blood-alcohol levels, but those devices don't test for other intoxicating substances. The new law allows police to sample oral fluids – mainly saliva – when they suspect an OWI.
Law enforcement groups that advocated for the law change say drug impairment is more difficult to identify than alcohol intoxication. Plus, intoxication levels can decrease between the time police make a traffic stop and a blood sample is collected.
"Oral fluid screening would give officers an additional, objective tool to confirm the presence of drugs – much like a preliminary breath test does for alcohol – before making an arrest decision," Dane County Sheriff Kalvin Barrett said at a December public hearing.
Wisconsin Act 99 became effective March 15, two days after Democratic Gov. Tony Evers signed it into law. The state Legislature passed it in February with bipartisan support.
Here's what to know about the new law:
What does the law allow police to do when they suspect an impaired driver?
If police have probable cause to believe a driver is intoxicated, the officer can request a saliva or breath test, or both. That's in addition to field sobriety tests.
The officer places a mouth swab inside the driver's cheek or under the tongue and runs it through a handheld device, such as Abbott's SoToxa or Alere DDS2.
The legislation was amended to allow the tests for suspected intoxicated operation of vehicles other than cars, such as boats, snowmobiles, ATVs, UTVs and more.
Are the oral drug tests admissible in court?
No. The test results aren't admissible in court and must be destroyed or returned to the person after the test is completed.
The preliminary tests are used only to help police decide whether to make an arrest and pursue laboratory confirmation testing.
Have police in Wisconsin tried saliva drug tests before?
Yes. The Dane County and Manitowoc County sheriff's offices piloted the program in 2016 and 2019, finding that oral fluid testing devices were accurate and consistent with blood tests.
Dane County conducted its study with the State Laboratory of Hygiene and published the results in an academic journal. The study found that 64% of participants arrested for an OWI also had one or more drugs in their blood, with THC the most common.
Manitowoc County worked with the State Laboratory of Hygiene and the Wisconsin State Patrol on its study, which collected 100 voluntary samples. Results showed 41% of OWI offenders were positive for THC, 20% for amphetamine and 14% for methamphetamine.
Which police agencies plan to use the new saliva drug test?
Wisconsin Chiefs of Police Association President Danny Thompson said he wasn't aware of any agencies immediately using the test.
"Although this roadside test will be very beneficial to arresting dangerous, impaired drivers, we have not heard of any agencies ready to implement this kind of testing right away," Thompson said in a statement to the Milwaukee Journal Sentinel.
A Milwaukee Police Department spokesperson said the department isn't using the tests "at this time and are still looking into it." A Milwaukee County Sheriff's Office spokesperson didn't respond to a request for comment.
The two departments that piloted the program also don't plan to bring it back right away.
Manitowoc County Sheriff Daniel Hartwig said his office is monitoring guidance related to the new law but doesn't have plans to implement it at this point. A Dane County Sheriff's Office spokesperson said the county would use it "given the appropriate funding and resources."
How much would the program cost?
Each SoToxa device appears to cost around $4,500 to $5,000, according to news reports on programs in North Dakota and San Diego.
Law enforcement groups said agencies in Wisconsin would likely pursue funding for the devices through federal grants.
Do other states use saliva screening?
Yes. A state-by-state analysis from the National Alliance to Stop Impaired Driving shows 10 states have statewide roadside oral fluid testing programs, and another eight have the program in some jurisdictions.
A 2021 report from the National Conference of State Legislatures found nearly half of states have the law, but few used it. One that does is Indiana, where over 200 handheld test devices are used across 110 law enforcement agencies.
Who authored and supported the law?
The bill was authored by Republicans, including Sen. Jesse James from Thorp and Rep. Barbara Dittrich from Oconomowoc. Several Democrats became cosponsors, including Rep. Lori Palmeri from Oshkosh and Rep. Ryan Spaude from Ashwaubenon.
Supporters of the bill included AAA Wisconsin, the Milwaukee Police Association, the Wisconsin Chiefs of Police Association and Mothers Against Drunk Driving. No groups registered in opposition to the bill.
What qualifies as operating while intoxicated in Wisconsin?
According to the Wisconsin Department of Transportation and state law, a driver is considered to be operating while intoxicated if:
- The driver is under the influence of an intoxicant, controlled substance or other drug that impairs their ability to safely operate a vehicle, even if the vehicle isn't in motion at the time of the traffic stop.
- The driver has a detectable amount of a restricted controlled substance in their blood. That includes cocaine, heroin, meth, delta-9 THC (if at a concentration of one or more nanograms per milliliter in a person's blood) and more.
- The driver has a BAC over what the law allows, such as above 0.08 for first-time offenders, 0.04 for commercial drivers or 0.02 for drivers with three or more prior OWIs.
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