North Carolina declared the practice of dentistry to be a matter of public concern requiring regulation. The North Carolina State Board of Dental Examiners (D) is “the agency of the State for the regulation of the practice of dentistry.” D may file suit to “perpetually enjoin any person from . . . unlawfully practicing dentistry.” Otherwise, D administers the practice of dentistry. A majority of the board’s members are engaged in the active practice of the profession it regulates. Dentists started whitening teeth. By 2003 nondentists performed the same function and charged much lower prices. D investigated even though D's own enabling act does not, by its terms, specify that teeth whitening is “the practice of dentistry.” D began issuing cease-and-desist letters on its official letterhead to nondentist teeth whitening service providers and product manufacturers. In 2010, the Federal Trade Commission (P) filed an administrative complaint charging the Board with violating §5 of the Federal Trade Commission Act. P alleged that the action to exclude nondentists from the market for teeth whitening services in North Carolina constituted an anticompetitive and unfair method of competition. D moved to dismiss, alleging state-action immunity. An ALJ denied the motion. On appeal, P sustained the ALJ’s ruling. It held that D is a “public/private hybrid” that must be actively supervised by the State to claim immunity. The ALJ conducted a hearing and determined that D had unreasonably restrained trade in violation of antitrust law. P won again on appeal. The Court of Appeals for the Fourth Circuit affirmed P in all respects. The Supreme Court granted certiorari.