In the United States v. Von's Grocery Co. et al., 1965, the U.S Supreme Court ruled that a merger between two grocery chains in Los Angeles violated Section 7 of the Clayton Act, which prohibits mergers and acquisitions where the effect may substantially lessen competition or tend to create a monopoly. The case was brought by the government against Von’s Grocery Company and Shopping Bag Food Stores after they merged in 1960 to form one entity controlling just over seven percent of LA’s retail grocery market share. Despite this relatively small percentage, it was enough for Justice Potter Stewart to write for majority stating that even minor increases in concentration could have anti-competitive effects under certain circumstances. This decision has been criticized as overly strict because it seemed to suggest any increase in concentration would violate antitrust laws regardless of actual competitive impact.

In the dissenting opinion for United States v. Von's Grocery Co., Justice Stewart disagreed with the majority's interpretation of Section 7 of the Clayton Act, arguing that it was not intended to prevent all mergers and acquisitions which might potentially decrease competition. He contended that this broad interpretation would stifle growth in American businesses and hinder economic progress. According to him, a more reasonable approach would be to only prohibit those mergers which create a monopoly or substantially lessen competition. In this case, he did not believe that merging two relatively small grocery chains in Los Angeles could significantly impact competitive conditions in such an extensive market area.