In the case of Lake Superior Consolidated Iron Mines v. Lord et al., 1925, the U.S. Supreme Court was asked to determine whether a Minnesota tax law that imposed higher taxes on iron ore than other minerals violated the Equal Protection Clause of the Fourteenth Amendment. The plaintiffs, owners and lessees of iron mines in Minnesota, argued that they were being unfairly singled out for taxation while operators of non-ferrous metal mines were taxed at lower rates. However, the court ruled against them stating that it is within a state's power to classify different kinds of property for purposes of taxation and such classification does not violate equal protection if there is reasonable basis for it. In this case, since iron ore mining had significantly greater impact on public resources compared with other types of mining due to its scale and nature (requiring more infrastructure like roads), differential taxing was justified.

The dissenting opinion in the case of Lake Superior Consolidated Iron Mines v. Lord et al., argued that the majority's decision to uphold a Minnesota statute imposing a tax on iron ore was incorrect. The dissenters believed that this law violated the Due Process Clause of the Fourteenth Amendment, as it imposed an unfair and arbitrary burden on interstate commerce. They contended that since iron ore is not manufactured or sold within Minnesota but rather transported across state lines for these purposes, it should be considered part of interstate commerce and thus exempt from state taxation under federal law. Furthermore, they disagreed with the majority's view that this tax did not discriminate against out-of-state businesses because all companies extracting minerals in Minnesota were subject to it; instead, they asserted such uniform application does not negate its discriminatory impact on those involved in interstate trade.