"Montana Firearms Freedom Act".

(1) The 10th amendment to the United States constitution guarantees to the states and their people all powers not granted to the federal government elsewhere in the constitution and reserves to the state and people of Montana certain powers as they were understood at the time that Montana was admitted to statehood in 1889. The guaranty of those powers is a matter of contract between the state and people of Montana and the United States as of the time that the compact with the United States was agreed upon and adopted by Montana and the United States in 1889.
http://data.opi.mt.gov/bills/2009/billhtml/HB0246.htm