California Penal Code § 1170

Initial Sentencing  
...
(a)(1) The Legislature finds and declares that the purpose of sentencing is public safety achieved through punishment, rehabilitation, and restorative justice. When a sentence includes incarceration, this purpose is best served by terms that are proportionate to the seriousness of the offense with provision for uniformity in the sentences of offenders committing the same offense under similar circumstances.
...
(2) The Legislature further finds and declares that programs should be available for inmates, including, but not limited to, educational, rehabilitative, and restorative justice programs that are designed to promote behavior change and to prepare all eligible offenders for successful reentry into the community. The Legislature encourages the development of policies and programs designed to educate and rehabilitate all eligible offenders. In implementing this section, the Department of Corrections and Rehabilitation is encouraged to allow all eligible inmates the opportunity to enroll in programs that promote successful return to the community. The Department of Corrections and Rehabilitation is directed to establish a mission statement consistent with these principles.