California Code, Family Code - FAM § 9340

(a) Any person who has been adopted under this part may, upon written notice to the adoptive parent, file a petition to terminate the relationship of parent and child.  The petition shall state the name and address of the petitioner, the name and address of the adoptive parent, the date and place of the adoption, and the circumstances upon which the petition is based.

(b) If the adoptive parent consents in writing to the termination, an order terminating the relationship of parent and child may be issued by the court without further notice.

(c) If the adoptive parent does not consent in writing to the termination, a written response shall be filed within 30 days of the date of mailing of the notice, and the matter shall be set for hearing.  The court may require an investigation by the county probation officer or the department.