What is the burden of proving the rule of judicial deference?

Turning to whether the trial court properly applied the rule of judicial deference in the case before us, we begin by noting the judicial deference rule is an affirmative defense. ( Ekstrom, supra, 168 Cal.App.4th at pp. 1122-1123, 86 Cal.Rptr.3d 145 ["Just as the corporate business judgment rule" is a defense, "so to[o] is the rule of judicial deference to decisions of homeowner association boards articulated in Lamden "].) Thus, the defendant has the burden of establishing *941 the requisite elements for applying the rule. ( Seltzer v. Barnes (2010) 182 Cal.App.4th 953, 969, 106 Cal.Rptr.3d 290 [defendant bears burden of proof on affirmative defense].) ⁷