Mont. Code Ann. § 85-5-108

For the purposes of carrying out the provisions of Title 85, chapter 5, parts 1 through 3, each commissioner appointed by the court has the authority to enter upon any ditch, canal, aqueduct, or other source for conveying the waters affected by the decree and to visit, inspect, and adjust all headgates or other means of distributing the waters and has the same powers as a sheriff or constable to arrest any person interfering with the distribution made by the commissioner, to be dealt with according to law.