On the last day of the 2008-2009 term, the United States Supreme Court issued an important decision addressing the National Bank Act and issues of federal preemption. In a 5-4 decision, the Court held in Cuomo v. Clearing House Assoc., LLC that states can enforce nonpreempted state consumer protection laws against national banks in court. In Cuomo, the Office of the Comptroller of the Currency (OCC) and a banking trade group challenged the ability of the attorney general for the state of New York to request nonpublic information regarding the lending practices of several national banks in order to determine whether the banks had violated New York’s fair lending laws. Specifically, the OCC and the Clearing House Association argued that the National Bank Act and an OCC regulation promulgated under the National Bank Act prohibited the New York attorney general’s state law enforcement against national banks.

The Court held that the OCC’s regulation purporting to preempt state law enforcement is not a reasonable interpretation of the National Bank Act. At issue was whether the National Bank Act’s limitation on the exercise of "visitorial powers" over national banks precluded state enforcement actions. Writing for the majority, Justice Antonin Scalia held that when "a state attorney general brings suit to enforce state law against a national bank, he is not acting in the role of sovereign-as-supervisor, but rather in the role of sovereign-as-law-enforcer. Such a lawsuit is not an exercise of ‘visitorial powers.’" Thus, he concluded that the OCC erred by extending the definition of "visitorial powers" in its regulation.

Justice Scalia further stated: "If a State chooses to pursue enforcement of its laws in court, then it is not exercising its power of visitation and will be treated like a litigant. An attorney general acting as a civil litigant must file a lawsuit, survive a motion to dismiss, endure the rules of procedure and discovery, and risk sanctions if this claim is frivolous or his discovery tactics abusive." In this case, the Court found that the administrative subpoenas threatened to be issued by the New York attorney general were not an exercise of the power of law enforcement and thus the Court upheld the injunction issued by the lower courts as applied to the threatened subpoenas but vacated the injunction insofar as it prohibited the New York attorney general from bringing a judicial enforcement action.

Justice Clarence Thomas, with whom Chief Justice John G. Roberts Jr., Justice Anthony M. Kennedy and Justice Samuel Anthony Alito Jr. joined, dissented. Justice Thomas agreed with the majority that there was ambiguity as to the meaning of the statutory term "visitorial powers" but concluded that the OCC’s interpretation was reasonable and therefore entitled to deference.