Minn. Stat. § 15.185: MAILING LISTS.

A department, agency, or official of the state issuing for public distribution any book, document, journal, map, pamphlet, or report on a regular basis to a list of persons who have asked to receive regular publications shall insert into at least one publication per person per year a returnable card which must be returned by that person in order to receive future similar publications from that department, agency, or official.