Utah Code Title 78B. Judicial Code § 78B-6-806. Necessary parties defendant

(1) No person other than the tenant of the premises, a lease signer, and subtenant if there is one in the actual occupation of the premises when the action is commenced, may be made a party defendant in the proceeding, except as provided in Section 78B-6-1111. A proceeding may not abate, nor the plaintiff be nonsuited, for the nonjoinder of any person who might have been made a party defendant. If it appears that any of the parties served with process or appearing in the proceedings are guilty, judgment shall be rendered against those parties.

(2) If a person has become a subtenant of the premises in controversy after the service of any notice as provided in this part, the fact that the notice was not served on the subtenant is not a defense to the action. All persons who enter under the tenant after the commencement of the action shall be bound by the judgment the same as if they had been made parties to the action.

(3) A landlord, owner, or designated agent is a necessary party defendant only in an abatement by eviction action for an unlawful drug house as provided in Section 78B-6-1111.