The United States Supreme Court case, UNITED STATES v. NATIONAL ASSOCIATION OF REAL ESTATE BOARDS ET AL., 1949, revolved around the Sherman Act's application to a restraint of trade by real estate boards. The National Association of Real Estate Boards and other defendants were charged with conspiring to fix commission rates for services rendered by member brokers in selling or leasing real property - an alleged violation of the Sherman Act. The District Court dismissed the complaint on grounds that it did not state a cause of action under this act because these activities didn't constitute "trade or commerce among several states." However, upon appeal, the Supreme Court reversed this decision stating that such practices could indeed be considered as partaking in interstate commerce and thus fell within purview of federal antitrust laws. Therefore, fixing commission rates was deemed illegal since it restrained competition and violated provisions set forth by the Sherman Act.

In the dissenting opinion for United States v. National Association of Real Estate Boards et al., 1949, it was argued that the majority's decision to hold real estate boards accountable under antitrust laws was a misinterpretation of these laws' intent and scope. The dissenters believed that such professional associations were not engaged in trade or commerce as defined by antitrust legislation but rather provided services within their profession. They contended that applying antitrust law to these organizations would unduly broaden its reach, potentially encompassing any group with economic influence regardless of whether they engage in traditional commercial activities. Furthermore, they expressed concern about potential negative impacts on self-regulation within professions if professional associations could be held liable for anti-competitive behavior simply due to setting standards or guidelines within their industry.