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A new government-funded study finds that marijuana DUI laws in nearly 20 states may be punishing drivers who are not actually impaired. These laws use fixed THC blood limits—similar to alcohol DUI standards—to automatically presume impairment. But the study shows this approach does not align with science, because THC can remain detectable in the body for days or even weeks after use, long after any effects on driving have worn off. As a result, regular cannabis users can test over the legal limit despite being sober and driving safely.
The study, published in Clinical Chemistry and partially funded by the National Institutes of Health, examined heavy cannabis users who abstained for 48 hours before blood testing and driving-simulator evaluations. Researchers found no reliable link between THC blood levels and driving impairment, reinforcing earlier research showing marijuana increases crash risk far less than alcohol. Unlike alcohol, which typically clears the body within one to two days, THC is stored in fat and can be detected for up to 30 days. The authors concluded that THC blood-limit laws lack scientific credibility and should not be used alone to determine impairment, recommending instead that law enforcement rely on observed driving behavior and field assessments while better testing methods are developed. Read the full story.
Referenced article written by Aaron Houston. Published on December 30, 2025 by Marijuana Moment.
