California Code, Welfare and Institutions Code - WIC § 331

(a) If a person has applied to the social worker, pursuant to Section 329, to commence juvenile court proceedings and the social worker does not file a petition within three weeks after the application, the person may, within one month after making the application, apply to the juvenile court to review the decision of the social worker, and the court may either affirm the decision of the social worker or, if it finds that the child is, prima facie, described by Section 300, order the social worker to commence juvenile court proceedings.

(b) If the probate court has referred a matter to the child welfare agency pursuant to Section 1513 of the Probate Code, and the agency does not file a petition to commence juvenile court proceedings within three weeks of the referral, the probate court or counsel appointed by the probate court pursuant to Section 1470 of the Probate Code to represent the child may, within one month after the referral, request that the juvenile court review the decision of the social worker not to file a petition.  The request shall contain the probate court referral made pursuant to subdivision (b) of Section 1513 of the Probate Code and the social worker's report, if available to the court, and need not contain any additional information.  The juvenile court may either affirm the decision of the social worker or, if it finds that the child is, prima facie, described by Section 300, order the social worker to commence juvenile court proceedings.