Sec. 37.006.  PARTIES.  (a)  When declaratory relief is sought, all persons who have or claim any interest that would be affected by the declaration must be made parties.  A declaration does not prejudice the rights of a person not a party to the proceeding.
(b)  In any proceeding that involves the validity of a municipal ordinance or franchise, the municipality must be made a party and is entitled to be heard, and if the statute, ordinance, or franchise is alleged to be unconstitutional, the attorney general of the state must also be served with a copy of the proceeding and is entitled to be heard.
Acts 1985, 69th Leg., ch. 959, Sec. 1, eff. Sept. 1, 1985.