In the 1946 case United Brotherhood of Carpenters and Joiners of America v. United States, the Supreme Court held that labor unions could be prosecuted under antitrust laws for activities such as secondary boycotts or strikes aimed at forcing employers to stop doing business with other companies. The court ruled that these actions were not protected by federal labor law exemptions from antitrust legislation because they involved more than just a dispute between workers and their immediate employer; rather, they affected commerce more broadly. This decision marked an important limitation on union power, indicating that while unions had certain rights to organize and bargain collectively, these rights did not extend to practices deemed harmful to competition in general.

The dissenting opinion in the United States v. United Brotherhood of Carpenters and Joiners of America case argued that labor unions should not be subject to antitrust laws, as they are fundamentally different from business enterprises. The justices contended that the Sherman Act was designed to prevent monopolistic practices by businesses, not collective bargaining activities by workers' organizations. They believed that applying these laws to unions would undermine their ability to negotiate for better working conditions and wages effectively. Furthermore, they disagreed with the majority's interpretation of "restraint of trade," arguing it shouldn't include actions taken during labor disputes because such an expansive definition could potentially criminalize any union activity aimed at improving worker rights or benefits.