DUI Legal Limits

It is illegal to operate or be in control of a motor vehicle on a public road anywhere in the United States while legally impaired by drugs or alcohol.

That said, states make their own laws governing specifics, and each of them is free to define what constitutes legal impairment in their own way.


All states have adopted a blood alcohol content level (BAC) of 0.08 as the formal legal limit. If you are found, via a blood test or Breathalyzer, to have a BAC of 0.08 or higher, that is normally high enough to get you convicted anywhere in the United States. Depending on the circumstances, however, you could be arrested if the police officer on the scene has probable cause to believe you have a BAC of 0.05.

In Arizona, however, you can be charged and possibly convicted under DUI laws even if you are nowhere near a 0.08 BAC, if the police officer can prove you were impaired even to the slightest degree.

Generally, if you are below drinking age, any BAC level is enough to earn you an arrest and possible conviction since it’s illegal for you to be drinking alcohol in the first place. If you’re under drinking age, the law generally presumes you are impaired at any BAC above zero.

Commercial Drivers

If you are operating a commercial vehicle, the law is even more stringent: You could be found guilty of a DUI if your BAC is 0.04 or greater, nationwide.


While marijuana remains a controlled substance under federal law, a number of states have already legalized possession, personal recreational use, medicinal use, or all of the above within their own borders.

According to information from the Governor’s Highway Safety Association, nine states have zero tolerance for operating a vehicle with THC or metabolites in your system. They include Arizona, Delaware, Georgia, Illinois, Indiana, Oklahoma, Rhode Island, South Dakota, and Utah.

Three states have zero tolerance for THC but no metabolite restrictions. They include Iowa, Michigan and Wisconsin.

Five states have established a max legal limit for THC: Montana (5 ng), Nevada (2 ng), North Dakota (2 ng), Pennsylvania (1 ng), and Washington (5 ng). If you are found to be driving with a THC concentration at or above these levels, these states’ laws define you to be impaired per se.

Colorado operates by reasonable inference.

Note that in some states, even possession can be enough to get your driver’s license suspended for up to six months.

This article is for general informational purposes only and is not intended to constitute legal advice. If you have been arrested for DUI or any other offense, you should immediately seek the services of an attorney licensed to practice law in your state.

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