In the Supreme Court of New Hampshire v. Piper case in 1984, the court ruled that a state cannot prohibit non-residents from practicing law within its jurisdiction. Kathleen R. Piper, a resident of Vermont but not New Hampshire, was denied admission to the bar in New Hampshire due to her residency status. The Supreme Court held that this violated Clause 1 of Article IV and the Equal Protection Clause of the Fourteenth Amendment which guarantees citizens equal privileges and immunities across all states. The court argued that there was no substantial reason for New Hampshire's discrimination against out-of-state residents as they were equally capable of serving clients' interests effectively and responsibly as local attorneys.

In the dissenting opinion for Supreme Court of New Hampshire v. Piper, 1984, Justice Powell argued that states should have the right to determine their own bar admission rules without interference from the Privileges and Immunities Clause. He believed that a state's decision to limit its bar membership to residents does not violate this clause as it is based on legitimate local concerns such as availability for court proceedings and familiarity with local laws and customs. Furthermore, he contended that non-residents are not being denied any fundamental rights since they can still practice federal law or be admitted pro hac vice in specific cases within the state. Therefore, according to him, there was no substantial reason why residency could not be used as a criterion for bar admission.