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 Maryland, the state enforces a zero-tolerance policy for underage drinking and driving. Drivers under the age of 21 are subject to Maryland's zero-tolerance law, which sets the blood alcohol concentration (BAC) level at .02 for underage drivers. If an underage driver is found operating a vehicle with a BAC of .02 or higher, they can be charged with a DUI (Driving Under the Influence) or DWI (Driving While Impaired). For drivers of any age, the per se intoxication level in Maryland is .08, and driving with a BAC at or above this level will result in a DUI charge. However, for minors with a BAC less than .08 but above .02, the charge will typically fall under the zero-tolerance law, potentially leading to a DWAI (Driving While Ability Impaired) charge. Penalties for underage DUI/DWI can include fines, license suspension, and mandatory participation in alcohol education programs. The specific offenses, punishments, and legal terminology for underage DUI/DWI are detailed in Maryland's Transportation Code and Criminal Law Code.