A court cannot rely on Welfare and Institutions Code section 778 to modify a minor’s placement to CYA. The minor here was placed in various group homes and as well as in a sexual offender treatment program; each of these placements failed. The probation department filed a petition under section 778, seeking to modify the placement and commit the minor to the Youth Authority because all other options had been exhausted. The minor unsuccessfully objected to this procedure, and on appeal the appellate court reversed, holding that section 777 is the exclusive statutory mechanism for a juvenile court to modify a prior placement order by committing a minor to CYA. The court rejected the People’s argument that Proposition 21, by making the grounds for a change of placement under section 777 more specific, had altered the intent of section 778 to include scenarios where a juvenile requires a change in placement due to reasons other than his own misconduct. Because section 778 was not modified by Proposition 21, the court could not rewrite the statute to conform to the People’s proposed interpretation.