In the case of Federal Trade Commission v. Jantzen, Inc., 1966, the Supreme Court ruled in favor of the Federal Trade Commission (FTC). The FTC had charged Jantzen with deceptive practices under Section 5 of the Federal Trade Commission Act for misrepresenting their swimwear as having a slimming effect on wearers' figures. The company argued that its advertising was merely "puffery" and not meant to be taken literally by consumers. However, both lower courts and ultimately the Supreme Court disagreed with this argument. They found that Jantzen's claims were indeed misleading because they suggested specific physical effects from wearing their products which could not be substantiated scientifically or otherwise proven true. Therefore, it was determined that these advertisements constituted unfair trade practices under federal law.

The dissenting opinion in the Federal Trade Commission v. Jantzen, Inc., case argued that the majority's decision to uphold FTC's cease and desist order against Jantzen was incorrect. The dissenters believed that there was no substantial evidence proving that Jantzen had engaged in unfair methods of competition or deceptive acts as defined by Section 5 of the Federal Trade Commission Act. They contended that a company should not be penalized for merely making truthful statements about its products, even if such statements might have an adverse effect on competitors. Furthermore, they disagreed with the majority’s interpretation of “unfairness” under Section 5, arguing it was too broad and could potentially stifle legitimate business practices and competition.