rule of reason
rule of reason. Antitrust. The judicial doctrine holding that a trade practice violates the Sherman Act only if the practice is an unreasonable restraint of trade, based on economic factors. See SHERMAN ANTITRUST ACT; RESTRAINT OF TRADE . Cf. PER SE RULE. [Cases: Monopolies 12(1.10). C.J.S. Monopolies §§ 47–52, 72, 78, 80–82, 105.]