The Federal Trade Commission v. Gratz et al., 1919, was a case in which the U.S Supreme Court ruled on whether or not the Federal Trade Commission (FTC) had jurisdiction to regulate unfair methods of competition. The defendants were a partnership doing business as Warren, Jones & Gratz and they were accused by FTC of using deceptive practices to manipulate prices in the grain market. They argued that their actions did not constitute "unfair methods of competition" under Section 5 of the FTC Act because it didn't involve interstate commerce directly but rather affected it indirectly through manipulation at local exchanges. However, the court held that even indirect effects on interstate commerce could be regulated by FTC if such activities involved unfair competitive practices. Therefore, any manipulative or deceptive practice affecting commerce is within its purview regardless if it's direct or indirect effect on interstate trade.

In the dissenting opinion for Federal Trade Commission v. Gratz et al., Justice McReynolds disagreed with the majority's interpretation of "unfair methods of competition" under Section 5 of the Federal Trade Commission Act. He argued that this phrase should be interpreted narrowly, only applying to practices that directly harm competitors and not those which merely deceive consumers. In his view, false advertising did not constitute an unfair method of competition because it did not necessarily result in injury to a competitor; rather, it was primarily harmful to consumers who were misled by such advertisements. Therefore, he believed that false advertising fell outside the scope of what Congress intended to regulate through Section 5 and thus was beyond FTC’s jurisdiction.