There are various criminal charges for operating a motorized, electric, or otherwise-powered transportation device on public roadways or waterways while under the influence of or intoxicated by drugs or alcohol, as defined by state law. DUI, DWI, OUI, OWI, and BUI—driving under the influence, driving while intoxicated, operating under the influence, operating while intoxicated, and boating under the influence—are some of the common names for such impaired-driving or impaired-operating criminal offenses.

Laws regarding the definitions and names of such alcohol and drug-related driving offenses vary from state to state and are usually located in a state’s statutes—often in the penal code or criminal code.

In Maine, the relevant offense for operating a vehicle while under the influence of alcohol or drugs is known as Operating Under the Influence (OUI). Maine law prohibits operating a motor vehicle, aircraft, watercraft, or any other motorized form of transport while under the influence of intoxicants, which include alcohol, drugs, or a combination of both. The legal blood alcohol content (BAC) limit in Maine is 0.08% for drivers 21 years of age or older, 0.04% for commercial drivers, and any detectable amount for drivers under the age of 21. Penalties for an OUI conviction can include fines, license suspension, and even jail time, depending on the circumstances and whether it is a first or subsequent offense. Maine's OUI laws are primarily found in Title 29-A of the Maine Revised Statutes, specifically in sections dealing with motor vehicles and traffic regulations.