In the United States v. Women's Sportswear Manufacturers Association et al., 1948, the Supreme Court ruled on a case involving an alleged violation of antitrust laws by a trade association and its members. The defendants were accused of conspiring to fix prices and restrict competition in the women's sportswear industry, which was deemed illegal under Section 1 of the Sherman Act. The court found that there was sufficient evidence to prove that such conspiracy existed among manufacturers who controlled over 80% of production in this market segment across several states. This decision reaffirmed that any agreement or concerted action between competitors with intent to restrain commerce is unlawful regardless if it directly affects interstate commerce or not; even indirect effects can be significant enough for federal jurisdiction under antitrust laws.

The dissenting opinion in the case of United States v. Women's Sportswear Manufacturers Association et al., 1948, argued that the majority had overstepped its bounds by interpreting the Sherman Act too broadly. The dissenters believed that there was a lack of evidence to suggest any anti-competitive behavior on part of the defendants and thus, they should not be held liable for violating antitrust laws. They contended that simply being members of an association did not automatically make them guilty of conspiratorial conduct or collusion to restrict trade or competition. Furthermore, they expressed concern about potential negative implications this ruling could have on legitimate business practices and associations in future cases if left unchecked.