In the case of Federal Trade Commission v. Ruberoid Co., the Supreme Court ruled in favor of the Federal Trade Commission (FTC). The FTC had accused Ruberoid Co. of violating antitrust laws by engaging in price discrimination and exclusive dealing contracts, which were deemed to lessen competition or create a monopoly. The court held that these practices could indeed stifle competition and potentially lead to monopolistic control over certain markets, thus infringing on antitrust regulations designed to maintain fair business operations across industries. This ruling reinforced the power of federal agencies like FTC in regulating commercial activities for protecting consumer interests and ensuring competitive market conditions.

In the dissenting opinion of Federal Trade Commission v. Ruberoid Co., Justice Jackson disagreed with the majority's decision to uphold FTC's cease and desist order against Ruberoid for its exclusive dealing contracts. He argued that such contracts are not inherently illegal under Section 3 of the Clayton Act unless they substantially lessen competition or create a monopoly, which he believed was not proven in this case. Furthermore, he contended that FTC should have provided clear guidelines on what constitutes "unfair methods of competition" instead of making arbitrary decisions based on individual cases. This lack of clarity could potentially deter businesses from engaging in legitimate competitive practices due to fear of punishment by FTC without any clear standards or rules to follow. Thus, Justice Jackson concluded that it is essential for courts and administrative agencies like FTC to provide definite standards when interpreting laws related to business conduct.