State of Arizona v. Maricopa County Med Soc.

In State of Arizona v. Maricopa County Med Soc., 457 U.S. 332 (1982), the U.S. Supreme Court affirmed that the antitrust laws automatically prohibit price-fixing even for maximum fees that professionals (physicians) would charge. The Court applied the per se rule of illegality to price-fixing that limited the maximum fees charged.

In the case, 70% of physicians in Maricopa County (which includes Phoenix) agreed not to charge patients more than set fees for specific services. The physicians argued that this benefited consumers (patients), but the Court found it to be automatically illegal under the antitrust laws due to the risk of abuse whenever any horizontal (among competitors) price-fixing occurs.