When a court acts under Penal Code section 17 to specify that a conviction for driving under the influence is a misdemeanor, that offense cannot later be pled as a prior felony conviction under Vehicle Code section 23550.5 even if it was originally punished as a felony. The unambiguous language of section 17 requires that the offenses be treated as a misdemeanor “for all purposes.” There is no relevant exception in former section 23175.5 (current section 23550.5) or in its legislative history to this clear mandate. Therefore, the judgment in this case had to be reversed and remanded to the trial court with instructions to vacate the finding of a prior felony violation.