Mont. Code Ann. § 40-15-406

This state or a local governmental agency or a law enforcement officer, prosecuting attorney, clerk of court, or any state or local governmental official acting in an official capacity is immune from civil liability for an act or omission arising out of the registration or enforcement of a foreign protection order or the detention or arrest of an alleged violator of a foreign protection order if the act or omission was done in good faith in an effort to comply with this part.