Notwithstanding the provisions of any other law the commission in any contested case shall give reasonable notice to representatives of associations or other interested groups or persons who have registered their names with the secretary of the commission for that purpose, to all parties and to cities and municipalities which the commission deems to be interested in the proceeding. The commission may prescribe an annual fee to be paid into the state treasury which shall be a charge to all registered groups or persons. This charge is to cover the costs involved.
"Contested case" means a proceeding before the commission in which the legal rights, duties or privileges of specific parties are required by law or constitutional right to be determined after a hearing.