After June 30, 1972, no new rural water districts shall be organized under the provisions of sections 46-1001 to 46-1020. Attempted formations of rural water districts under sections 46-1001 to 46-1020 which have not been completed before July 1, 1972, shall be null, void and of no effect for the purpose of organizing such district. All rural water districts having valid corporate existence before July 1, 1972, shall enjoy all rights, duties, powers and authorities conferred by sections 46-1001 to 46-1020 and shall not be affected by this section, nor shall the legality of formation, organization, or operation of any such district be subject to any legal action based on this section.