In the 1984 case Williams et al. v. Vermont et al., the U.S Supreme Court ruled that Vermont's tax scheme, which taxed non-residents more heavily than residents on car purchases made out of state, was unconstitutional as it violated both the Commerce Clause and Equal Protection Clause of the Constitution. The plaintiffs were a group of non-residents who had purchased cars outside of Vermont but later moved to the state and were subjected to this higher taxation rate upon registering their vehicles in-state. They argued that they were being unfairly discriminated against based on their residency status at time of purchase. The court agreed with them, stating that there was no legitimate reason for such discrimination and thus struck down this aspect of Vermont's tax law.

In the dissenting opinion for Williams et al. v. Vermont et al., Justice Thurgood Marshall, joined by Justices Brennan and Blackmun, argued that Vermont's tax scheme violated the Equal Protection Clause of the Fourteenth Amendment because it discriminated against nonresidents who purchased cars outside of Vermont before moving to the state. The majority held that this discrimination was justified due to administrative convenience and ensuring tax compliance; however, Marshall contended these reasons were insufficient to justify such blatant discrimination. He pointed out that other states had found ways to ensure tax compliance without resorting to discriminatory practices and suggested that administrative convenience should not be used as an excuse for violating constitutional rights. Furthermore, he criticized the court's decision for setting a dangerous precedent where states could discriminate against new residents under vague justifications.