Mont. Code Ann. § 53-21-1332
53-21-1332 Decisions by guardian or conservator
53-21-1332 . Decisions by guardian or conservator. When a valid directive is in existence at the time of a judicial determination of incapacity and appointment of a guardian or conservator of the principal:
(1) a guardian or conservator shall comply with the instructions in a principal's directive and may not revoke the principal's directive unless the appointing court provides authorization; and
(2) absent a court order to the contrary, a health care decision of an agent takes precedence over that of a guardian or conservator.