I believe part of the Montana bill states that Montana will defend whoever is arrested/fined/whatever by the feds.
That section was struck out. Law as-passed
Law proposed and REJECTED:
NEW SECTION. Section 7. Duties of the attorney general. (1) A Montana citizen whom the government of the United States attempts to prosecute, under the congressional power to regulate interstate commerce, for violation of a federal law concerning the manufacture, sale, transfer, or possession of a firearm, a firearm accessory, or ammunition manufactured and retained within Montana must be defended in full by the Montana attorney general. (2) Upon written notification to the Montana attorney general by a Montana citizen of intent to manufacture a firearm, a firearm accessory, or ammunition to which [sections 1 through 7] apply, the attorney general shall seek a declaratory judgment from the federal district court for the district of Montana that [sections 1 through 7] are consistent with the United States constitution.