You get pulled over, arrested, and booked on a DUI. Your license goes into suspension limbo, you get a court date, and you face the same penalties alcohol would bring: fines, classes, probation, and in some cases jail. What makes a cannabis DUI different is the evidence. In most states there is no legal THC number to point at, so the case comes down to how you drove, how you looked, and what an officer says about your eyes and speech. That is a harder case to defend than a breathalyzer reading, and a harder one to prove.
Does weed have a legal limit?
Mostly no. A small number of states set a per se THC limit in blood, often 5 nanograms per milliliter, and a few of those also allow a defense if you can show you were not actually impaired. Other states use zero tolerance rules, meaning any detectable metabolite is enough to support a charge. The rest rely on what is called an impairment standard: the prosecution has to convince a jury you were too high to drive, using officer testimony and driving behavior.
Zero Tolerance Marijuana Driving States: A Practical Guide
Know which system you are in before you assume anything. A medical card does not shield you from a DUI charge in most states. Legal recreational status does not either. Driving is treated as a licensed privilege with conditions attached, and being under the influence of cannabis is one of those conditions in every state.
What happens at the stop
The officer watches you drive, then watches you talk. Expect questions about where you are coming from and what you have used. Expect standardized field sobriety tests, the walk and turn, the one leg stand, the horizontal gaze nystagmus check. Those tests were designed and validated for alcohol. Officers are trained to interpret them for other drugs, but the science behind that leap is thinner than it sounds on the report.
Many departments send out a Drug Recognition Expert, an officer with extra training in a twelve step evaluation that includes pulse, blood pressure, eye exams, and a dark room check. The DRE writes an opinion about which category of drug you are under. That opinion often becomes the backbone of the case.
Refusing the test
Every state has an implied consent law. By driving, you agreed to submit to chemical testing. Refuse, and you face a license suspension on the spot through an administrative process, separate from the criminal case. In many states the refusal can also be mentioned in court. You can still refuse. Just walk in knowing the trade: a suspension for refusing versus a blood result the prosecutor can quote.
Penalties for a first offense
A typical first cannabis DUI brings a fine in the hundreds to low thousands, a license suspension that ranges from a few months to a year, a drug education or treatment requirement, probation, and possibly an ignition interlock condition even though the device does nothing for cannabis. Jail time is possible but often suspended or reduced on a first offense with no crash and no priors.
It gets worse with aggravating facts: a child in the car, a collision, property damage, a prior DUI, or a high concentration in the blood draw. Commercial drivers face career consequences, since a DUI can knock out a CDL.
How a defense usually gets built
Blood results measure metabolites, and some metabolites linger for days or weeks after use. A number on a lab report does not tell anyone when you last smoked or whether you felt anything at the wheel. Defense work tends to focus on that gap, on the timing of the draw, on chain of custody, on whether the stop itself was lawful, and on the limits of the DRE opinion.
Dash and body camera footage matters more than people expect. So does the absence of bad driving. If the reason for the stop was a burned out taillight and you held your lane for five miles, that record helps.
The parts people forget
An arrest follows you past the courtroom. Insurance rates climb. Employers in driving, healthcare, and government work ask questions. Professional licenses can be reviewed. And a DUI, even a cannabis one, can make you inadmissible to Canada and can complicate a US border crossing in either direction. For a lot of people those collateral effects cost more than the fine.
First 48 hours
Say nothing to police beyond identifying yourself, and post nothing online. Write down what you remember while it is fresh: time of the stop, what you ate, when you last used, what tests were done. Then find a lawyer who handles DUI cases in that county, because the local rules on blood draws and administrative hearings vary a lot. Ask specifically about the deadline to request a license hearing, since it is often short, sometimes only days.