9. In a diversity case, how much weight should a federal appellate court give to a federal district court’s determination of state law? In SALVE REGINA COLLEGE v. RUSSELL, 499 U.S. 225, 111 S.Ct. 1217, 113 L.Ed.2d 190 (1991), the Court held that the court of appeals should conduct de novo review, just as it does when questions of federal law are in dispute.

Chief Justice Rehnquist authored a strong dissent in which Justice White and Justice Stevens joined:

Federal courts of appeals perform a different role when they decide questions of state law than they do when they decide questions of federal law. In the former case, these courts are not sources of law but only reflections of the jurisprudence of the courts of a State.

While in deciding novel federal questions, courts of appeals are likely to ponder the policy implications as well as the decisional law, only the latter need be considered in deciding questions of state law.