A court may modify any orders it issues in relation to a juvenile who is subject to its jurisdiction, provided that applicable procedural requirements are met. Courts are precluded from making arbitrary modifications, and they must be primarily concerned with the juvenile's welfare and rehabilitation. Courts do not have the authority to modify orders upon their own motion, but they may act pursuant to a petition filed by a concerned party. A party may properly petition for modification of an order under two circumstances: when changed circumstances or new evidence exist to justify a modification and when circumstances show that the previous disposition has not been effective in juvenile rehabilitation. The justification for the flexibility granted to courts under California's juvenile law seems simply to be that the primary purposes of the juvenile justice system (child welfare, development, and rehabilitation) demand it. Modification of a juvenile probation order will not always be proper because each case will vary according to the individual facts. 28 footnotes