Minn. Stat. § 410.09: REGULATION OF FRANCHISES.

Such proposed charter may provide for regulating and controlling the exercise of privileges and franchises in or upon the streets and other public places of the city, whether granted by the city, by the legislature, or by any other authority; but no perpetual franchise or privilege shall ever be created, nor shall any exclusive franchise or privilege be granted, unless the proposed grant be first submitted to the voters of the city, and be approved by a majority of those voting thereon, nor in such case for a period of more than 25 years.