What standard of review governs in a writ of administrative mandamus?

We commence our analysis with a statement of the appropriate standard of review since the parties disagree as to what standard of review governs their dispute. On appeal from a writ of administrative mandamus an appellate court must determine whether the decision of an administrative agency will substantially affect "vested, fundamental rights." (Bixby v. Pierno (1971) 4 Cal.3d 130, 143, 93 Cal.Rptr. 234, 481 P.2d 242.) When the administrative decision neither involves nor substantially affects such a right, the trial court must review the whole administrative record to determine whether the findings are supported by substantial evidence and whether the agency committed any errors of law. (Id. at p. 144, 93 Cal. Rptr. 234, 481 P.2d 242.)