Lawyers for Wells Fargo Bank squared off Thursday at the U.S. Court of Appeals for the Eleventh Circuit against those representing what they hope remains a class of plaintiffs challenging the bank's overdraft practices.

The question the judges were tasked with answering seemed deceptively simple: Did Wells Fargo forfeit its right to enforce arbitration clauses in its customers' contracts years after it began litigating the case in court and after the class had been certified by the trial court?

Wells Fargo argued that, while it had indeed litigated the claims of the named plaintiffs in the long-running dispute, the district court had erred by certifying a class of more than one million unnamed plaintiffs and ruling that they were not barred by the arbitration clause.