A person commits the offense of criminal mischief if the person knowingly or purposely:

(a) injures, damages, or destroys any property of another or public property without consent;

(b) without consent tampers with property of another or public property so as to endanger or interfere with persons or property or its use;

(c) damages or destroys property with the purpose to defraud an insurer; or

(d) fails to close a gate previously unopened that the person has opened, leading in or out of any enclosed premises. This does not apply to gates located in cities or towns.  

Please see Mont. Code Ann. section 45-6-101.