Mont. Code Ann. § 39-2-803

If a company or corporation in this state authorizes or allows any of its agents to blacklist or if a person does blacklist any discharged employee or attempts by word or writing or any other means to prevent any discharged employee or any employee who may have voluntarily left the company's service from obtaining employment with another person, except as provided for in 39-2-802, the company, corporation, or person is liable in punitive damages to the employee prevented from obtaining employment, to be recovered in a civil action, and is also punishable as provided in 39-2-804.