In Buss v. Superior Court (1997) 16 Cal. 4th 35, 59 65 Cal. Rptr. 2d 366, 939 P.2d 766, the California Supreme Court held that in a " 'mixed' " action in which some claims are potentially covered and others are not, the insurer must defend the action in its entirety, including those claims for which there is no potential coverage under the policy. This requirement is not a contractual one but rather is prophylactic. "To defend meaningfully," the court explained, "the insurer must defend immediately. To defend immediately, it must defend entirely. It cannot parse the claims, dividing those that are at least potentially covered from those that are not. To do so would be time consuming. It might also be futile: The 'plasticity of modern pleading' allows the transformation of claims that are at least potentially covered into claims that are not, and vice versa." ( Id. at p. 49.) Although the insurer must defend the action in its entirety, the insurer has an "implied-in-law" right to be reimbursed from the insured for defense costs allocable solely to claims that are not even potentially covered under the policy. ( Buss v. Superior Court, supra, 16 Cal. 4th at p. 51.) The reason is that the insurer has not received premiums and did not bargain to defend such claims; therefore, defending the entire action "unjustly enriches" the insured. ( Id. at p. 50.) The Supreme Court explained: "We cannot justify the insurer's duty to defend the entire 'mixed' action contractually, as an obligation arising out of the policy, and have never even attempted to do so. . . . That being said, we can, and do, justify the insurer's duty to defend the entire 'mixed' action prophylactically, as an obligation imposed by law in support of the policy. To defend meaningfully, the insurer must defend immediately. To defend immediately, it must defend entirely. It cannot parse the claims, dividing those that are at least potentially covered from those that are not. To do so would be time consuming. It might also be futile: The 'plasticity of modern pleading' allows the transformation of claims that are at least potentially covered into claims that are not, and vice versa." ( Id. at pp. 48-49.)