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 Idaho, the state enforces a zero-tolerance policy for underage drinking and driving. This means that any driver under the age of 21 who is found to have a blood alcohol concentration (BAC) of .02 or higher can be charged with Driving Under the Influence (DUI). Idaho's zero-tolerance law is stricter than some states that may allow a BAC up to .05 for underage drivers. For those under the legal drinking age, being caught with a BAC between .02 and .08 can lead to a DUI charge under the zero-tolerance law. However, if an underage driver has a BAC of .08 or more, they can be charged with the standard DUI offense, which is the same as for drivers of legal drinking age. Additionally, if there is no chemical test available, an officer's observation of signs of intoxication can also lead to a DUI charge. The specific penalties and procedures for underage DUI offenses in Idaho are detailed in the state's statutes, which can include fines, license suspension, and possible jail time, depending on the circumstances and any prior offenses.