What is the test for granting declaratory judgment de novo?

"The customary deference for the district court is not applicable to its determination to grant a declaratory judgment. The court of appeals must exercise its own sound discretion to determine the propriety of the district court's grant or denial of declaratory relief." United States v. Washington, 759 F.2d 1353, 1356-57 (9th Cir.) (en banc) (citations omitted), cert. denied, 474 U.S. 994, 106 S.Ct. 407, 88 L.Ed.2d 358 (1985); accord Guerra v. Sutton, 783 F.2d 1371, 1376 (9th Cir.1986) (the court reviews the denial of declaratory relief de novo).