The United States Supreme Court has upheld the constitutionality of the Montana coal severance tax finding that it does not violate the Commerce Clause and that it is not inconsistent with federal legislation.
Commonwealth Edison Company v. Montana, 453 U.S. 609 (1981).
Comfrey S. Ickes,
Constitutional Law - Commerce Clause - State Taxation of Interstate Commerce - Supremacy Clause,
Duq. L. Rev.
Available at: https://dsc.duq.edu/dlr/vol20/iss3/6