In the United States v. Connecticut National Bank et al., 1973, the Supreme Court was tasked with determining whether a bank's acquisition of shares in another company violated antitrust laws. The case arose when Connecticut National Bank acquired shares in Hartford National Corporation and its subsidiary banks. The U.S government argued that this acquisition would significantly reduce competition among national banks and violate Section 7 of the Clayton Act, which prohibits mergers or acquisitions that may lessen competition or create a monopoly. The District Court initially ruled in favor of the bank, stating that banking falls under an exemption from these antitrust laws due to their regulation by other federal statutes specifically designed for them. However, upon appeal to the Supreme Court, it reversed this decision. The Supreme Court held that while there are certain exemptions for banking activities under various regulatory statutes such as Banking Act of 1933 (Glass-Steagall Act) and Bank Holding Company Act of 1956; they do not exempt all aspects from general anti-trust scrutiny like those covered by Clayton act. Therefore, even though some specific practices might be allowed within banking industry regulations; if they have potential to substantially lessen competition or tend towards monopoly - they can still be challenged under broader anti-trust legislation like Clayton act.

In the dissenting opinion for United States v. Connecticut National Bank et al., Justice Douglas argued that the majority's decision to allow a bank merger despite potential antitrust concerns was misguided. He contended that the Court had failed to properly consider whether such a merger would be detrimental to competition in violation of Section 7 of the Clayton Act, which prohibits mergers and acquisitions where their effect may significantly reduce competition or tend towards monopoly. The justice believed that there were significant competitive risks associated with allowing large banks to merge without sufficient scrutiny, including higher prices and reduced services for consumers as well as an increased risk of financial instability due to concentration of economic power in fewer hands. He also criticized what he saw as undue deference by the Court towards banking regulators' approval of this particular merger, arguing instead for more rigorous judicial review when it comes to matters involving potential threats to market competition.