Most states have a zero-tolerance (or near zero-tolerance) blood alcohol concentration (BAC) level of .02 for drivers under the legal drinking age (usually 21) that will result in a DUI/DWI charge. Some states set the BAC level at which a minor may be charged with DUI/DWI at .05. And some states will charge a minor driving a vehicle with a BAC of less than the state’s per se intoxication level (usually .08) with violating a zero-tolerance law such as driving while ability impaired (DWAI)—but will charge a minor with a BAC of .08 or more with per se (pronounced purr-say) DUI/DWI based on the state’s BAC-level definition of intoxication—or, in the absence of a chemical test of blood, breath, or urine, will charge the minor with common law DUI/DWI based on the police officer’s belief the minor was driving while intoxicated.

DUI/DWI criminal offenses, punishments, and terms used for underage DUI/DWI vary from state to state. These laws are generally located in a state’s statutes—often in the penal code or criminal code.

In Montana (MT), the state enforces a zero-tolerance policy for underage drinking and driving. This means that for drivers under the age of 21, the state has set a lower blood alcohol concentration (BAC) limit than for those of legal drinking age. Specifically, Montana law stipulates that a minor may be charged with Driving Under the Influence of Alcohol (DUI) if they have a BAC of .02 or higher, which is significantly lower than the standard .08 BAC limit for drivers 21 and over. If a minor is found driving with a BAC of .08 or higher, they can be charged with the standard DUI offense, just like an adult. The penalties for underage DUI/DWI can include fines, license suspension, and possibly even jail time, depending on the circumstances and whether it is a first or subsequent offense. It's important for minors to understand that Montana takes underage drinking and driving very seriously, and the consequences can be severe.