As cannabis becomes legal for medical and recreational use in many U.S. states, a growing concern across the country is the impact of cannabis-impaired driving. Despite its legal status in several jurisdictions, driving under the influence of cannabis (DUIC) remains illegal and is treated as a serious offense, with laws evolving to address both public safety and legal consistency.
Under federal law, cannabis remains classified as a Schedule I controlled substance, which means it is still illegal to possess or use it on federal property or drive under its influence. However, states where cannabis has been legalized have developed their own regulations regarding DUIC. Currently, 24 states and Washington, D.C., have legalized adult-use cannabis, and nearly all have specific provisions that prohibit driving under the influence. States typically define impaired driving as operating a motor vehicle while one’s ability is affected to the extent that it is unsafe to do so. For cannabis, this includes both medical and recreational users. The challenge, however, lies in determining impairment. Unlike alcohol, where blood alcohol concentration (BAC) provides a measurable and widely accepted standard, cannabis impairment is more complex to assess due to the variability in how tetrahydrocannabinol (THC) affects individuals.
Some states have implemented “per se” laws, which set legal limits for THC levels in the bloodstream. For example, Colorado and Washington have a 5 nanograms per milliliter (ng/mL) THC blood limit. Drivers who test above this limit can be charged with DUI, even if they do not appear overtly impaired. However, critics argue that these limits may not accurately reflect impairment, especially for frequent users who may have higher residual THC levels without being intoxicated. Other states, such as California and New York, rely on behavioral and field sobriety tests administered by trained law enforcement officers, often with the support of Drug Recognition Experts (DREs). Some police departments also use saliva-based roadside testing kits, though their accuracy remains debated.
Penalties for cannabis-impaired driving are severe and can include fines, license suspension, mandatory drug education programs, and even jail time. In most states, a first offense is classified as a misdemeanor, but repeat offenses or cases involving injury or death can result in felony charges. For example, in California, a first DUI conviction can lead to a fine of up to $1,000, a six-month license suspension, and mandatory DUI education classes. If a person under 21 is caught driving under the influence, the state enforces a zero-tolerance policy, meaning any detectable level of THC could result in a DUI charge. Moreover, a DUI conviction can have long-term implications, such as increased insurance premiums, employment barriers, and travel restrictions to certain countries.
With cannabis use on the rise, public safety campaigns are intensifying efforts to educate drivers about the dangers of driving while high. According to the National Highway Traffic Safety Administration (NHTSA), cannabis can impair motor coordination, reaction time, and decision-making — all critical for safe driving. States are also investing in training more law enforcement officers to detect drug-impaired drivers and developing better testing methods to ensure accurate and fair enforcement of DUI laws.
While cannabis may be legal in many places, driving under its influence is not. As research and technology advance, the legal system will continue to evolve in balancing individual rights with public safety. In the meantime, the safest choice remains clear: if you’re high, don’t drive.