Wisconsin law prohibits any person from possessing or consuming an alcoholic beverage in a privately owned vehicle if:
The prohibition is applicable to everyone inside the car—the driver and passengers—and to all vehicles located on public highways.
Persons under 21. Persons under 21 years old aren't allowed to possess any alcoholic beverage in a vehicle, whether opened or sealed. The only exception to this rule is if the underage person is employed by a brewer or retailer and is transporting alcohol in the course of that employment.
Alcoholic beverage. Wisconsin defines "alcoholic beverage" to include any fermented beverage, wine, or intoxicating liquor. Uniquely, in Wisconsin, the open container restriction also applies to containers of nitrous oxide.
Certain vehicles. Wisconsin's open container law isn't applicable to passengers riding in certain types of vehicles, including statutorily authorized limousines and buses operated by a licensed chauffeur. Passengers inside these chauffeured vehicles are permitted to possess and consume alcohol. Of course, this exception doesn't apply to persons who are under 21 years of age.
Areas of the vehicle. Wisconsin's open container laws are intended to apply to the passenger areas of the vehicle, including the glove and utility compartments. The open container restrictions aren't applicable to items in the trunk of the car or to areas inaccessible to the driver or passengers if the car doesn't have a trunk.
An open container is a traffic violation in Wisconsin. A conviction will result in a fine of up to $100 but no jail time. A person may be arrested for an open container violation but generally must be released (as opposed to being taken to jail) unless other circumstances exist that justify further detention.
Violation of the open container law by a person operating a commercial vehicle will also result in an out-of-service order. The order, issued by the arresting officer, prohibits the operation of a commercial vehicle for an immediate 24 hours.
Offenders who are under 21 years old face a fine of $20 to $400. These underage offenders are also looking at a license suspension of up to one year for a first violation and up to two years for a second violation within 12 months.