Mont. Code Ann. § 17-5-104
Effect of revisions on bonds previously authorized
17-5-104 . Effect of revisions on bonds previously authorized. If prior to April 23, 1981, a political subdivision was authorized to issue bonds pursuant to a law that limited the rate of interest on the bonds, it may issue all of the bonds so authorized under the provisions of 17-5-102 even if the rate of interest on the bonds exceeds the maximum rate permissible prior to April 23, 1981.