The U.S. Supreme Court case Clarke, Comptroller of the Currency v. Securities Industry Association in 1986 revolved around whether national banks could sell discount securities under federal banking laws without registering as a broker-dealer under the Securities Exchange Act of 1934. The Securities Industry Association (SIA) argued that such activities were not part of the "business of banking" and thus required registration. However, the Comptroller disagreed and allowed banks to engage in these transactions without registration. The Supreme Court ruled in favor of Clarke, stating that selling discount securities was indeed within the scope of "the business of banking." The court reasoned that since these transactions did not involve any investment risk for banks - they merely acted as intermediaries between buyers and sellers - it fell within their purview. This ruling clarified an important aspect regarding what constitutes 'banking' activities for national banks and set a precedent allowing them to participate more broadly in financial markets.

In the dissenting opinion for Clarke v. Securities Industry Association, Justice White disagreed with the majority's interpretation of the National Bank Act. He argued that national banks have always been allowed to sell third-party securities as part of their banking business and this practice was not prohibited by any legislation or regulation until 1978 when it was challenged by a group of non-bank competitors. Furthermore, he pointed out that Congress had never intended to limit these activities but rather sought to regulate them in order to protect consumers from potential abuses. Therefore, according to Justice White, there is no statutory basis for prohibiting national banks from engaging in brokerage activities related directly or indirectly to selling third-party securities.