The Arrow-Hart & Hegeman Electric Co. v. Federal Trade Commission case in 1933 revolved around the question of whether a merger between two companies, Arrow Electric and Hart & Hegeman, violated the Clayton Act's prohibition against acquisitions that may substantially lessen competition or create a monopoly. The Federal Trade Commission (FTC) had initially ruled that the merger was illegal under this act due to its potential anti-competitive effects within their industry - electrical wiring devices manufacturing. However, on appeal to the Supreme Court, it was determined that while both firms were indeed competitors in some areas of their business operations, they did not dominate these markets nor would their consolidation result in any substantial lessening of competition or tendency towards monopoly creation as per FTC’s claims. Therefore, it was concluded by the court that there wasn't sufficient evidence for such an assertion and thus reversed FTC's order requiring divestiture.

In the dissenting opinion for Arrow-Hart & Hegeman Electric Co. v. Federal Trade Commission, Justice McReynolds disagreed with the majority's view that the company had violated antitrust laws by engaging in unfair methods of competition. He argued that there was no substantial evidence to support this conclusion and criticized the commission for failing to define what constituted an "unfair method." Furthermore, he contended that it was not within their jurisdiction to determine whether a business practice was fair or unfair without clear legislative guidelines. The justice also expressed concern about potential overreach by regulatory agencies and warned against allowing them too much discretion in interpreting vague statutory language.