Mont. Code Ann. § 3-10-704

If in any county there is no appointed constable, the board of county commissioners may, at the request of a party, after being satisfied that it is expedient to do so, specially deputize any proper person of suitable age not interested in the action to serve a summons, with or without an order to arrest the defendant and with or without a writ of attachment, or to serve an execution. The county commissioners are liable upon their official bonds for all official acts of the person so deputized. The appointment of the deputy shall be made in writing on the process, and a note thereof shall be made on the justice's docket.