The U.S. Supreme Court case Postal Telegraph Cable Company v. Alabama in 1894 revolved around the issue of whether a state could impose taxes on interstate commerce, specifically telegraph companies operating within its borders. The Postal Telegraph Cable Company argued that as an interstate business, it should not be subject to taxation by individual states like Alabama under the Commerce Clause of the Constitution which gives Congress exclusive power over interstate commerce regulation. However, the court ruled against them stating that while states cannot interfere with or tax interstate commerce directly, they can levy taxes on businesses operating within their jurisdiction if those taxes do not discriminate against out-of-state entities and are fairly apportioned based on in-state activities or property ownership. Therefore, Alabama's tax was upheld because it met these criteria.

In the dissenting opinion for Postal Telegraph Cable Company v. Alabama, Justice Brewer argued that the tax imposed by Alabama on out-of-state telegraph companies was unconstitutional. He contended that it violated both the Commerce Clause and Equal Protection Clause of the Constitution. According to him, this tax unfairly targeted interstate commerce as it only applied to businesses operating across state lines while exempting those functioning within a single state. Furthermore, he believed that such taxation could potentially lead to an undue burden on interstate commerce if every state followed suit with similar taxes. Additionally, he asserted that this law discriminated against non-resident corporations in violation of their equal protection rights under Fourteenth Amendment because resident corporations were not subjected to similar taxation.