The Absolute Sobriety law, also known as “Not a Drop”, makes it illegal for any person under the age of 21 to operate a motor vehicle with BAC greater than 0.00 but not more than 0.079. A BAC of 0.08 or greater will result in charges of operating a motor vehicle with a prohibited alcohol concentration.
https://docs.legis.wisconsin.gov/statutes/statutes/346/x/63/2m