The United States Supreme Court case, UNITED STATES v. UNITED STATES GYPSUM CO. et al., 1977, revolved around the issue of price fixing and whether it constituted a per se violation of the Sherman Act - an antitrust law that prohibits certain business activities deemed to be anti-competitive. The defendants in this case were six major manufacturers and distributors of gypsum board who had been accused by the government of conspiring to fix prices for their products through a mutual exchange program where they would share pricing information with each other. The court ruled in favor of the government stating that such practices did indeed constitute price-fixing which was illegal under federal law regardless if there was any intent or not behind these actions. However, it also clarified that while criminal liability could be imposed on companies for violating antitrust laws, proof beyond reasonable doubt about their intention to do so is necessary.

In the dissenting opinion for United States v. United States Gypsum Co., Justice Rehnquist disagreed with the majority's decision to apply a per se rule of illegality to price verification agreements among competitors, arguing that such an approach was too simplistic and failed to consider potential pro-competitive effects. He believed that these types of agreements could potentially enhance competition by reducing uncertainty in market transactions, thereby promoting efficiency and consumer welfare. Furthermore, he criticized the majority for not providing clear guidance on what constitutes "price fixing," which could lead to confusion and inconsistency in future cases. Instead, he advocated for a more nuanced analysis based on actual economic impact rather than presumptive categorizations.