In the case of Investment Company Institute et al. v. Camp, Comptroller of the Currency, et al., 1970, the U.S Supreme Court ruled that national banks could not operate collective investment funds that were functionally equivalent to mutual funds. The court held that such activities exceeded permissible banking practices under federal law and violated provisions of Glass-Steagall Act which separated commercial and investment banking operations in order to prevent conflicts of interest. This decision was based on an interpretation by Justice Harlan who argued that allowing banks to manage these types of investments would lead them into “the investment advisory business,” a line Congress intended for them not to cross when it passed the Glass-Steagall Act.

In the dissenting opinion for Investment Company Institute et al. v. Camp, Comptroller of the Currency, et al., Justice Harlan argued that national banks should be allowed to operate collective investment funds as part of their banking business under federal law. He believed that such activity was not prohibited by either the National Bank Act or the Glass-Steagall Act and did not pose a threat to commercial banking operations or public interest. Furthermore, he contended that it was within Congress's power to regulate these activities if they deemed necessary but until then, there were no legal grounds for prohibiting them. Therefore, in his view, courts should refrain from interfering with administrative decisions unless they clearly contradict statutory provisions.