(a) No declaration shall prejudice the rights of persons not parties to the proceeding.

(b) In any proceeding involving the validity of a municipal ordinance or franchise, the municipality shall be made a party and shall be entitled to be heard as a party.

(c) If a statute of the state, any order or regulation of any administrative body of the state, or any franchise granted by the state is alleged to be unconstitutional, the Attorney General of the state shall be served with a copy of the proceeding and shall be entitled to be heard.