Civil Code § 2929.45

(a) An assessment or lien to recover the costs of nuisance abatement measures taken by a governmental entity with regard to property that is subject to a notice of default, that is purchased at a foreclosure sale, or that is acquired through foreclosure under a mortgage or deed of trust, shall not exceed the actual and reasonable costs of nuisance abatement.

(b) A governmental entity shall not impose an assessment or lien unless the costs that constitute the assessment or lien have been adopted by the elected officials of that governmental entity at a public hearing.