In the 1906 case of Copper Queen Consolidated Mining Company v. Territorial Board of Equalization of the Territory of Arizona, the U.S. Supreme Court ruled in favor of the mining company, finding that its property had been unfairly overvalued for tax purposes by Arizona's territorial board. The court held that while states and territories have broad powers to levy taxes, they must do so in a manner consistent with due process rights under the Fourteenth Amendment. In this instance, it was found that there was no rational basis for valuing Copper Queen’s property at $5 million when similar properties were valued much lower; thus violating equal protection principles as well as due process rights. This decision underscored an important principle: taxation authorities cannot arbitrarily assign values to taxable properties but must adhere to fair standards and procedures.

In the dissenting opinion for Copper Queen Consolidated Mining Company v. Territorial Board of Equalization of the Territory of Arizona, Justice Harlan argued that there was no constitutional violation in assessing taxes on mining properties based on their gross output value rather than their physical property value. He contended that it is within a state's power to determine how best to tax its citizens and businesses as long as it does not violate any specific prohibitions in the Constitution or infringe upon federal jurisdiction. Furthermore, he believed that this method of taxation did not discriminate against interstate commerce because all mines within Arizona were taxed equally regardless if they sold their products out-of-state or locally. Therefore, he disagreed with the majority's ruling which found this form of taxation unconstitutional under both due process and equal protection clauses.