California Code, Family Code - FAM § 9306

(a) Except as provided in subdivisions (b) and (c), the birth parents of a person adopted pursuant to this part are, from the time of the adoption, relieved of all parental duties towards, and all responsibility for, the adopted person, and have no right over the adopted person.

(b) If an adult is adopted by the spouse of a birth parent, the parental rights and responsibilities of that birth parent are not affected by the adoption.

(c) An adult being adopted pursuant to this part may waive the termination of the parental duties and responsibilities of an existing parent or parents under subdivision (a) by signing a waiver at any time prior to the finalization of the adoption. The waiver may be included in the adoption agreement or in a separate writing filed with the court.