In the case of British-American Oil Producing Co. v. Board of Equalization of Montana, the Supreme Court ruled in favor of the state board in 1936. The dispute arose when British-American Oil argued that their property was being unfairly taxed by Montana's Board of Equalization due to an overvaluation compared to other properties within the state. The company claimed this violated both its rights under equal protection and due process clauses as outlined by the Fourteenth Amendment. However, after reviewing evidence presented from both sides, including tax assessments and valuation methods used for different properties across Montana, it was determined that there were no substantial differences or discrimination against out-of-state companies like British-American Oil which would constitute a violation under these constitutional provisions.

The dissenting opinion in the case of British-American Oil Producing Co. v. Board of Equalization of Montana disagreed with the majority's decision that Montana's tax on oil produced within its borders was unconstitutional due to it violating the Commerce Clause and Due Process Clause. The dissent argued that there was no violation as the tax applied equally to all oil producers, regardless if they were local or out-of-state companies, thus not discriminating against interstate commerce. They also contended that since this is a property tax levied on extracted resources before their entry into commerce, it does not interfere with interstate trade but rather falls under state jurisdiction over natural resources within its territory for taxation purposes.