How do we review a district court's interpretation of state law de novo?

We review a district court's interpretation of state law de novo. Ravell v. United States, 22 F.3d 960, 961 n. 1 (9th Cir.1994). When interpreting state law, federal courts are bound by decisions of the state's highest court. In re Kirkland, 915 F.2d 1236, 1238 (9th Cir.1990). "In the absence of such a decision, a federal court must predict how the highest state court would decide the issue using intermediate appellate court decisions, decisions from other jurisdictions, statutes, treatises, and restatements as guidance." Id. at 1239. ²