Comparing law abiding people with stoners? Apples and oranges.
After legalization, one can be a both a user and a law-abiding person. The non-law-abiding were already using, and driving while stoned, before legalization - so also represent no increase in DUI after legalization.
Someplace or other I heard that William F. Buckley once sailed his yacht outside US territorial waters to try pot without violating US law.