Any law restricting business practices that are considered unfair or monopolistic. Among U.S. laws, the best known is the Sherman Antitrust Act of 1890, which declared illegal “every contract, combinationelipsisor conspiracy in restraint of trade or commerce.” The Clayton Antitrust Act of 1914, as amended in 1936 by the Robinson-Patman Act, prohibits discrimination among customers through prices or other means; it also prohibits mergers or acquisitions whenever the effect may be “to substantially lessen competition.” Labour unions are also subject to antitrust laws.

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(1890) First U.S. legislation enacted to curb concentrations of power that restrict trade and reduce economic competition. Proposed by Sen. John Sherman, it made illegal all attempts to monopolize any part of trade or commerce in the U.S. Initially used against trade unions, it was more widely enforced under Pres. Theodore Roosevelt. In 1914 Congress strengthened the act with the Clayton Antitrust Act and the formation of the Federal Trade Commission. In 1920 the U.S. Supreme Court relaxed antitrust regulations so that only “unreasonable” restraint of trade through acquisitions, mergers, and predatory pricing constituted a violation. Later cases reinforced the prohibition against monopoly control, including the 1984 break-up of AT&T. Seealso antitrust law.

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