California Code, Welfare and Institutions Code - WIC § 387

(a) An order changing or modifying a previous order by removing a child from the physical custody of a parent, guardian, relative, or friend and directing placement in a foster home, or commitment to a private or county institution, shall be made only after noticed hearing upon a supplemental petition.

(b) The supplemental petition shall be filed by the social worker in the original matter and shall contain a concise statement of facts sufficient to support the conclusion that the previous disposition has not been effective in the rehabilitation or protection of the child or, in the case of a placement with a relative, sufficient to show that the placement is not appropriate in view of the criteria in Section 361.3.

(c) Notwithstanding subdivision (a), dependency jurisdiction shall be resumed for a child as to whom dependency jurisdiction has been suspended pursuant to Section 366.5 if the jurisdiction established pursuant to Section 601 or 602 is terminated and if, after the issuance of a joint assessment pursuant to Section 366.5, the court determines that the court's dependency jurisdiction should be resumed.

(d) Upon the filing of the supplemental petition, the clerk of the juvenile court shall immediately set the same for hearing within 30 days, and the social worker shall cause notice thereof to be served upon the persons and in the manner prescribed by Sections 290.1 and 291, except that service under this subdivision may be delivered by electronic service pursuant to Section 212.5.

(e) An order for the detention of the child pending adjudication of the petition may be made only after a hearing is conducted pursuant to Article 7 (commencing with Section 305).