In many states it is a criminal offense (DUI/DWI) to operate a commercial vehicle with a blood alcohol concentration of .04 or more—which is half of the BAC usually required to commit the DUI/DWI offense while driving a non-commercial vehicle. Because most holders of commercial driver’s licenses (CDLs) depend on their license to earn a living, the consequences of a DUI/DWI conviction for a CDL holder—including a conviction while operating a non-commercial vehicle—are serious.

Laws vary from state to state but a CDL holder’s license may be suspended for one year for the first offense, and with a second DUI/DWI conviction the CDL holder may be permanently disqualified from holding a CDL.

These laws are generally located in a state’s statutes—often in the vehicle code, motor vehicle code, or transportation code.

In Maine, it is indeed a criminal offense for a commercial vehicle operator to have a blood alcohol concentration (BAC) of .04 or higher, which is stricter than the .08 BAC limit for non-commercial drivers. This is in accordance with federal regulations that apply to all states. For holders of a Commercial Driver's License (CDL), the consequences of a DUI (driving under the influence) conviction can be severe, especially given their reliance on their license for employment. Under Maine law, a first-time DUI offense can result in a one-year suspension of the CDL. If a CDL holder commits a second DUI offense, they face the possibility of a lifetime disqualification from holding a CDL. These regulations are designed to promote safety on the roads and ensure that commercial vehicle operators adhere to higher standards of sobriety given the potential risks associated with operating larger vehicles. The specific laws governing DUI offenses for CDL holders in Maine can be found in the state's motor vehicle statutes.