The United States Supreme Court case, UNITED STATES v. PHILLIPSBURG NATIONAL BANK & TRUST CO. et al., 1969, revolved around the issue of bank mergers and their potential to create a monopoly or reduce competition significantly in violation of Section 7 of the Clayton Act. The government challenged a proposed merger between two New Jersey banks - Phillipsburg National Bank and Trust Company (PNB) and First National Bank & Trust Co. of Easton (FNB). The District Court initially ruled in favor of the banks stating that there was no substantial lessening of competition due to this merger as it would not have any significant effect on commerce outside Pennsylvania's Lehigh Valley area where these banks were located. However, upon appeal by the U.S Government, the Supreme Court reversed this decision arguing that even if commercial effects are localized within one state’s boundaries, they can still be considered interstate commerce under federal antitrust laws if they substantially affect people living outside those borders who do business with firms inside them.

In the dissenting opinion for United States v. Phillipsburg National Bank & Trust Co., Justice Hugo Black argued that the majority's decision to block a merger between two banks based on potential harm to competition was misguided. He contended that the Clayton Act, which prohibits mergers and acquisitions where the effect may be substantially to lessen competition or tend to create a monopoly, should not apply in this case because it did not involve manufacturing or commerce industries but rather banking industry which is regulated differently. Furthermore, he believed that there was no substantial evidence showing that such a merger would indeed lead to lessened competition within any section of the country as required by law before blocking such transactions under antitrust laws.