These white license tags — known officially as special registration plates — always feature the letter "W" followed by a second letter and a series of numbers. Issued primarily to drivers convicted of driving drunk, they have taken on the nickname "whiskey plates" as whiskey represents the letter "W" in the NATO phonetic alphabet.Minnesota is one of two states that under certain conditions require DWI offenders to surrender their traditional plates and replace them with whiskey plates — the other is Ohio...Under Minnesota law, courts are required to order drivers to display whiskey plates if their first DWI offense resulted from having a blood alcohol content (BAC) of at least 0.16% — twice the legal limit for driving. The special tags are also mandatory for drivers convicted of several DWIs within 10 years, DWI with a child under 16 in the vehicle, or refusing to take a BAC test within 10 years of a DWI conviction.
Details about their issuance, implementation, implications etc in a longread at the StarTribune.