The U.S. Supreme Court case State of Wyoming v. State of Oklahoma in 1991 revolved around a dispute between the two states over an Oklahoma law that required coal-burning power plants within the state to burn at least 10% Oklahoma-mined coal. Wyoming, a major exporter of low-sulphur coal, argued that this statute violated the Commerce Clause by discriminating against interstate commerce and favoring in-state economic interests. The Supreme Court ruled in favor of Wyoming, finding that while states have significant authority to regulate their own economies and natural resources, they cannot enact legislation which disrupts or discriminates against interstate commerce without clear justification for doing so under local concerns or public interest considerations. In this case, it was determined that Oklahoma's law did not meet these criteria and thus infringed upon federal regulation governing interstate trade.

In the dissenting opinion for State of Wyoming v. State of Oklahoma, Justice Scalia disagreed with the majority's decision that Oklahoma's statute requiring in-state coal-burning utilities to burn a mixture containing at least 10% Oklahoma-mined coal violated the Commerce Clause. He argued that this case was not about discriminatory legislation but rather about preferential treatment for local business, which he believed did not violate the Constitution. Scalia contended that if every state law favoring local businesses were considered unconstitutional under the Commerce Clause, then many longstanding and widely accepted practices would also be deemed unconstitutional. He further asserted that it is up to Congress - not courts - to decide whether such laws are harmful or beneficial on balance to national commerce.