Montana Title 2. Government Structure and Administration § 2-9-103. Actions under invalid law or rule--same as if valid--when

(1) If an officer, agent, or employee of a governmental entity acts in good faith, without malice or corruption, and under the authority of law and that law is subsequently declared invalid as in conflict with the constitution of Montana or the constitution of the United States, that officer, agent, or employee, any other officer, agent, or employee of the represented governmental entity, or the governmental entity is not civilly liable in any action in which the individuals or governmental entity would not have been liable if the law had been valid.

(2) If an officer, agent, or employee of a governmental entity acts in good faith, without malice or corruption, and under the authority of a duly promulgated rule or ordinance and that rule or ordinance is subsequently declared invalid, that officer, agent, or employee, any other officer, agent, or employee of the represented governmental entity, or the governmental entity is not civilly liable in any action in which liability would not attach if the rule or ordinance had been valid.