By the time the California Court of Appeals issued its opinion in the state litigation, the federal litigation had returned to the district court on remand from this, court. On October 1, 2001, some three months after the decision of the California Court of Appeals, the defendants filed a Renewed Motion for Summary Judgment in the district court. The defendants argued that the outcome of the state litigation barred the federal court from further consideration of claims of unlawful retaliation. In November 2001, the district court granted summary judgment in favor of the defendants, deeming the net effect of the state litigation to be preclusive of the federal litigation either via res judicata or via collateral estoppel. DiRuzza v. County of Tehama, No. S-96-596 (E.D.Cal. Nov. 21, 2001). It is that 2001 district court decision which DiRuzza now appeals.
STANDARD OF REVIEW
This court reviews a district court’s summary judgment order de novo, viewing all facts and reasonable inferences therefrom in the light most favorable to the nonmoving party. Clicks Billiards, Inc. v. Sixshooters, Inc., 251 F.3d 1252, 1257 (9th Cir.2001); Warren v. City of Carlsbad, 58 F.3d 439, 441 (9th Cir.1995). Granting summary judgment is appropriate “if the pleadings, depositions, answers to interrogatories, and admissions on file, together with the affidavits, if any, show that there is no genuine issue as to any material fact and that the moving party is entitled to a judgment as a matter of law.” Fed.R.Civ.P. 56(c).
In determining the preclusive effect of a state-court judgment, this court must “refer to the preclusion law of the State in which judgment was rendered.” Marrese v. Am. Acad. of Orthopaedic Surgeons, 470 U.S. 373, 380, 105 S.Ct. 1327, 84 L.Ed.2d 274 (1985).
DISCUSSION
As noted above, the district court found that both res judicata and collateral estop-pel justified summary judgment on DiRuz-za’s federal claims. For the reasons that follow, we agree with the district court’s determination that the state litigation precludes further pursuit by DiRuzza of the federal litigation. But we confine our holding to collateral estoppel.
Collateral estoppel, or issue preclusion, dictates “ ‘that when an issue of ultimate fact has once been determined by a valid and final judgment, that issue cannot again be litigated between the same parties in any future lawsuit.’ ”
People v. Santamaria, 8 Cal.4th 903, 35 Cal.Rptr.2d 624, 884 P.2d 81, 84 (1994) (quoting
Ashe v. Swenson, 397 U.S. 436, 443, 90 S.Ct. 1189, 25 L.Ed.2d 469 (1970)). The Supreme Court of California has described its application of the doctrine as follows:
Collateral estoppel precludes relitigation of issues argued and decided in prior proceedings. Traditionally, we have applied the doctrine only if several threshold requirements are fulfilled. First, the issue sought to be precluded from relitigation must be identical to that decided in a former proceeding. Second, this issue must have been actually litigated in the former proceeding. Third, it must have been necessarily decided in the former proceeding. Fourth, the decision in the former proceeding must be final and on the merits. Finally, the party against whom preclusion is sought must be the same as, or in privity with, the party to the former proceeding.
Lucido v. Superior Court, 51 Cal.3d 335, 272 Cal.Rptr. 767, 795 P.2d 1223, 1225 (1990) (citations omitted).
The parties do not question that the fourth and fifth elements of collateral es-toppel are present here: there is a final