In the 1995 case of Barnett Bank of Marion County, N. A. v. Bill Nelson, Florida Insurance Commissioner et al., the U.S Supreme Court ruled in favor of Barnett Bank by a unanimous decision (9-0). The issue at hand was whether federal law permitted national banks to sell insurance in small towns even if state laws prohibited it. The court held that Federal law allowing national banks located in towns with less than 5,000 people to act as agents for insurance companies preempted conflicting state regulations prohibiting such activities under certain conditions or circumstances. This ruling clarified that when a federal and state law are in conflict over banking practices, the federal law takes precedence.

In the dissenting opinion for Barnett Bank of Marion County, N. A. v. Bill Nelson, Florida Insurance Commissioner et al., Justice Thomas argued that the majority misinterpreted federal law to preempt a state statute prohibiting national banks from selling insurance in small towns. He contended that Congress did not intend to grant such broad powers to national banks and thus override state laws designed to protect consumers from potential conflicts of interest inherent in bank-insurance combinations. According to him, the National Bank Act's silence on this issue should be interpreted as allowing states' regulatory authority over insurance sales by banks within their borders rather than precluding it.