California Code, Family Code - FAM § 9102

(a) Except as provided in Section 9100, an action or proceeding of any kind to vacate, set aside, or otherwise nullify an order of adoption on any ground, except fraud, shall be commenced within one year after entry of the order.

(b) Except as provided in Section 9100, an action or proceeding of any kind to vacate, set aside, or nullify an order of adoption, based on fraud, shall be commenced within three years after entry of the order, or within 90 days of discovery of the fraud, whichever is earlier.

(c) In any action to set aside an order of adoption pursuant to this section or Section 9100, the court shall first determine whether the facts presented are legally sufficient to set aside the order of adoption. If the facts are not legally sufficient, the petition shall be denied. If the facts are legally sufficient, the court's final ruling on the matter shall take into consideration the best interests of the child, in conjunction with all other factors required by law.

(d) The department shall not be required under any circumstances to investigate a petition filed pursuant to this section or to represent a child who is the subject of a proceeding under this section.