In the case of Michigan National Bank v. Robertson et ux., the U.S. Supreme Court addressed a dispute over whether or not federal law preempted state law in relation to bank mergers. The Robertsons, shareholders in a national bank that was merging with another national bank under the authority of federal banking laws, sought to block this merger by invoking provisions from Michigan's state corporation laws which required shareholder approval for such transactions. The court ruled 5-4 in favor of Michigan National Bank, stating that when it comes to matters involving national banks, federal law takes precedence over conflicting state regulations. Therefore, even though Michigan’s corporate statutes would have required shareholder approval for such a merger transaction if both entities were incorporated within its jurisdictional boundaries; these requirements did not apply because one entity involved was operating under federally granted charter powers and thus subject only to applicable Federal banking regulations.

In the dissenting opinion for Michigan National Bank v. Robertson et ux., Justice Douglas argued that the majority's decision to allow a national bank to charge interest rates based on where it is located, rather than where the loan transaction occurs, undermines state usury laws designed to protect consumers from predatory lending practices. He contended that this interpretation of federal banking law could lead national banks to "shop around" for states with lenient usury laws and set up their main offices there in order to exploit borrowers in other states with stricter regulations. Furthermore, he expressed concern about potential negative impacts on local economies and small businesses if out-of-state lenders can undercut them by offering loans at lower interest rates due only to differences in state laws rather than competitive market forces.