Mont. Code Ann. § 28-2-701

What is unlawful

That is not lawful which is:

(1) contrary to an express provision of law;

(2) contrary to the policy of express law, though not expressly prohibited; or

(3) otherwise contrary to good morals.

History:
En. Sec. 2240, Civ. C. 1895
Re-en. Sec. 5051, Rev. C. 1907
Re-en. Sec. 7553, R.C.M. 1921
Cal. Civ. C. Sec. 1667
Field Civ. C. Sec. 827
Re-en. Sec. 7553, R.C.M. 1935
R.C.M. 1947, 13-801.