The U.S. Supreme Court case Commonwealth Edison Co. et al. v. Montana et al., 1980, revolved around the constitutionality of a Montana state tax on coal mined within its borders and sold to out-of-state utilities for electricity generation purposes, with the plaintiffs arguing that it violated both the Commerce Clause and Due Process Clause of the Constitution. The court ruled in favor of Montana, upholding the tax as constitutional by a vote of 6-3. The majority opinion held that states have broad taxing powers under their inherent sovereignty unless specifically limited by federal law or constitutionally prohibited; neither was found applicable here. They also rejected arguments that this was an unfair burden on interstate commerce since all coal mined in Montana - whether used locally or shipped out-of-state - was subject to same rate taxation (30% severance tax). Furthermore, they dismissed claims about due process violation stating there's sufficient connection between state services provided and businesses taxed. This decision underscored states' rights to levy taxes on natural resources extracted within their boundaries even if those resources are destined for use elsewhere.

In the dissenting opinion for Commonwealth Edison Co. v. Montana, Justice Harry Blackmun argued that the majority's decision to uphold Montana's coal severance tax was inconsistent with previous rulings on interstate commerce and taxation. He contended that the tax placed an unfair burden on out-of-state consumers of Montana coal, violating principles of fair apportionment and non-discrimination in state taxation of interstate commerce. Blackmun also criticized the court for failing to adequately consider whether or not this type of tax could lead to economic protectionism by states, which would be detrimental to a national economy dependent on free trade between states.