Supreme Court of New Hampshire v. Piper

Article 4, Section 2 includes a section known as the Privileges and Immunities Clause. One of several items intended at the nation's formation to create a national economic union, the Privileges and Immunities Clause gave citizens of one state the right to conduct business in another state on equal terms with that state's citizens. The clause was not used as commonly as the Commerce Clause, which protects interstate commerce. Although Alexander Hamilton, in The Federalist, called the idea that no state could discriminate against the citizens of another state "the basis of the Union," the Supreme Court had largely interpreted the Privileges and Immunities Clause as meaning that states needed to show good reason in order to discriminate against non-residents. Nonetheless, the district court and the court of appeals both affirmed that the residency requirement denied Piper her rights under the Privileges and Immunities Clause, finding that the opportunity to practice law was a "fundamental right" that was being denied her.

The New Hampshire Supreme Court argued that there were substantive reasons for the residency requirement. Nonresidents, it argued, would have fewer reasons than residents to familiarize themselves with local rules and procedures, and would be less likely "to behave ethically, to be available for court proceedings, and to do pro bono and other volunteer work in the State." The U.S. Supreme Court, like the two courts preceding it, determined that these were not substantial enough reasons for discrimination. The practice of law, wrote Justice Powell in the Court opinion, was not an exercise of state power that justified a residency requirement. Furthermore, his opinion suggested that there were positive benefits to having out-of-state residents practice law in a state. For instance, they might be more likely to represent people raising unpopular federal claims.