Several shareholders of Fannie Mae filed a derivative suit on behalf of the company after Fannie Mae had announced one of the largest corporate earning restatements in history. The first derivative suit was dismissed, and James Kellmer, along with Arthur Middleton and L. Jay Agnes, all of whom were shareholders, filed new derivative suits that were consolidated by the district court. Fannie Mae moved to dismiss the cases presented by Kellmer and Middleton, but not Agnes. In 2008, Congress passed the Housing and Economic Recovery Act (HERA), which established a new federal agency, FHFA, that became Fannie Mae's conservator. Soon after its creation, the FHFA intervened in the derivative actions, arguing that HERA endowed it with sole authority to litigate claims belonging to Fannie Mae. The district court granted the FHFA's motion and followed the court decision by moving for voluntary dismissal without prejudice or a 180-day stay of litigation, arguing that the FHFA needed more time to evaluate if proceeding with the suit would further the conservatorship's statutory purposes. The district court granted FHFA's motion to dismiss without prejudice for Agnes and granted Fannie Mae's motion to dismiss Kellmer and Middleton with prejudice. Shareholders Kellmer and Agnes appealed the substitution order, and the FHFA appealed the district court's favorable ruling for Fannie Mae. Why would the FHFA appeal the district court's dismissal of Kellmer and Middleton when the FHFA filed a motion to voluntarily dismiss the cases? This case is about who has the right to file a derivative suit. What was the core reason behind the appeals court's decision in regards to Kellmer's and Agnes's appeal? [Kellmer v. Raines, 674 F.3d 848 (2012).]