§ 37.006.Parties

The joinder provision, and its two halves protect different people.

When declaratory relief is sought, all persons who have or claim any interest that would be affected by the declaration must be made parties.

"Must be made parties" is mandatory, and it is a real requirement. A declaration purporting to settle rights in an instrument without joining everyone claiming under it settles nothing durable.

A declaration does not prejudice the rights of a person not a party to the proceeding.

That is the protection for the absent party, and it is also the sanction for failing to join. A party who leaves out an interested person obtains a declaration that does not bind them, and may have to litigate the same question again.

The two sentences work as a pair: one requires joinder, the other makes the failure to join self-defeating rather than merely improper.

Subsection (b) addresses public law challenges. Where a proceeding involves the validity of a municipal ordinance or franchise, the municipality must be made a party and is entitled to be heard.

And where a statute, ordinance, or franchise is alleged to be unconstitutional, the attorney general must also be served with a copy of the proceeding and is entitled to be heard.

The distinction between the two is worth noting. The municipality must be made a party; the attorney general must be served and may be heard, without being joined.

The reason is that the state has an interest in the defence of its statutes even where it is not a litigant — and a constitutional holding reached without the state’s participation is one nobody defended.

Service on the attorney general is easy to overlook and consequential, since a constitutional challenge mounted without it is vulnerable on that ground alone.