In the case City of Pittsburgh v. Alco Parking Corp et al., 1973, the Supreme Court ruled in favor of Alco Parking Corporation and other parking lot operators, stating that a city ordinance which imposed higher tax rates on commercial parking lots than on non-commercial ones was unconstitutional. The court found that this differential taxation violated the Equal Protection Clause of the Fourteenth Amendment as it discriminated against certain businesses without any rational basis for doing so. The city argued that commercial lots caused more traffic congestion and therefore should be taxed at a higher rate to offset these costs; however, no evidence was presented to support this claim. Therefore, the court concluded there was no reasonable justification for treating commercial and non-commercial parking lots differently under tax law.

In the dissenting opinion for the case City of Pittsburgh v. Alco Parking Corp., it was argued that the majority's decision to uphold a city ordinance imposing a tax on non-residents who park their cars in commercial lots within city limits, while exempting residents from this tax, violated principles of equal protection under law. The dissenters contended that there was no rational basis for distinguishing between resident and non-resident users of parking facilities in terms of either benefits received or burdens imposed upon them by municipal services. They further asserted that such discriminatory taxation could potentially lead to retaliatory measures by surrounding municipalities against city residents using similar services outside the city limits, thereby creating an undesirable situation where local governments are pitted against each other in taxing individuals based on residency status rather than actual use or benefit derived from public services.