The U.S. Supreme Court case Loewe v. Lawlor, also known as the Danbury Hatters' Case, was a landmark decision in 1907 that expanded the application of the Sherman Antitrust Act to labor unions engaged in secondary boycotts. The United Hatters of North America had initiated a nationwide boycott against D.E. Loewe & Co., after it refused to recognize and negotiate with their union. The court ruled that such actions constituted an illegal restraint on trade under federal law because they interfered with interstate commerce by coercing retailers and customers not to engage with non-union businesses like D.E.Loewe & Co.. This ruling effectively made secondary boycotts - where workers pressure third parties not directly involved in a labor dispute - illegal for many years until laws were changed during the New Deal era.

In the dissenting opinion for Loewe v. Lawlor, Justice Oliver Wendell Holmes Jr. argued that the Sherman Act should not be applied to labor unions as they were not engaged in commerce but rather in a struggle with their employers over wages and working conditions. He contended that strikes by workers did not constitute an illegal restraint of trade or commerce under the law because they were merely refusing to work on terms offered by their employer, which was within their rights. Furthermore, he asserted that if every act done with intent to influence another's business decisions could be considered an attempt at monopolization or restraint of trade, then almost any human action could fall under this category - a notion he found absurd and contrary to common sense understanding of these concepts.