What is the standard of review in an action to set aside a determination under CEQA?

"'In an action to set aside an agency's determination under [CEQA], the appropriate standard of review is determined by the nature of the proceeding below. . . . [S]ection 21168 "establishes the standard of review in administrative mandamus proceedings" under Code of Civil Procedure section 1094.5 while section 21168.5 "governs traditional mandamus actions" under Code of Civil Procedure section 1085. [Citation.] The former section applies to proceedings normally termed "quasi-adjudicative," "in which by law a hearing is required to be given, evidence is required to be taken and discretion in the determination of facts is vested in a public agency . . . ." [Citations.] The latter section applies to all other actions taken pursuant to CEQA and generally encompasses "quasi-legislative" decisions made by a public agency. [Citations.]' [Citations.]" (Gentry v. City of Murrieta (1995) 36 Cal.App.4th 1359, 1374-1375.)

"The distinction, however, is rarely significant. In either case, the issue before the trial court is whether the agency abused its discretion. Abuse of discretion is shown if (1) the agency has not proceeded in a manner required by law, or (2) the determination is not supported by substantial evidence. [Citations.]" (Gentry v. City of Murrieta, supra, 36 Cal.App.4th at p. 1375.) "'Review under administrative mandamus ( 21168) and review under traditional mandamus ( 21168.5) share many of the same characteristics. There is no practical difference between the standards of review applied under traditional or administrative mandamus.' [Citation.]" (California Native Plant Society v. City of Santa Cruz (2009) 177 Cal.App.4th 957, 984.)

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