The opinion of the court was delivered by: Baxter, J.
Prison regulations promulgated by the California Department of Corrections and Rehabilitation (CDCR) set forth the procedures and substantive requirements for validating an inmate as a member or associate of a prison gang. Because gangs "present a serious threat to the safety and security of California prisons" (Cal. Code Regs., tit. 15, § 3023, subd. (b)), validation of an inmate as a gang member or associate can result in the inmate's placement in a security housing unit (SHU).
The current dispute arose when the CDCR validated petitioner Elvin Cabrera as a gang associate--i.e., "an inmate . . . who is involved periodically or regularly with members or associates of a gang." (Cal. Code Regs., tit. 15, § 3378, subd. (c)(4) (hereafter section 3378)). Under section 3378, validation of an inmate as an "associate" requires at least three "independent source items of documentation indicative of association" with persons who have been classified as gang members or associates. (Ibid.) At least one of the source items must be a "direct link" to a current or former gang member or associate. (Ibid.)
The question presented for our review, which involves the meaning of this prison regulation, is very narrow. In essence, the CDCR contends that the Court of Appeal erred by independently interpreting the scope of the regulation's requirement of a "direct link" between the inmate and a gang member or associate with respect to one category of source items--a category called "Association" (§ 3378, subd. (c)(8)(G))--instead of deferring to the CDCR's interpretation of its own regulation.*fn1 For the reasons that follow, we agree the Court of Appeal failed to accord due deference to the CDCR's interpretation of its own regulations, and therefore reverse the judgment awarding habeas corpus relief and remand the matter to the Court of Appeal for further proceedings.
In 2003, Cabrera was convicted of robbery, burglary, receiving stolen property, and possession of drug paraphernalia. He was sentenced to prison for 62 years to life. He is incarcerated at the California Correctional Institution at Tehachapi.
On May 13, 2008, Cabrera was officially identified--or "validated," in the words of the CDCR regulation (§ 3378, subd. (c)(4))--as an associate of the Mexican Mafia prison gang. The validation was based on the discovery in his prison cell of several photocopied drawings containing symbols distinctive to the gang. Two of the drawings were signed by validated affiliates*fn2 of the Mexican Mafia.
Cabrera challenged his validation through the CDCR administrative appeal process, but his appeal was denied. Cabrera then filed a petition for writ of habeas corpus in Kern County Superior Court. The superior court denied the petition, finding that his validation as a gang associate was supported by three source items of gang validation with two direct links to gang affiliates.
Cabrera filed an original petition in the Court of Appeal, which issued an order to show cause and then granted relief in a published opinion. The Court of Appeal's decision to grant relief rested on a disagreement with the CDCR over the interpretation of the CDCR's own regulation. In the view of the Court of Appeal, the regulation providing that at least one source item indicative of association with validated gang affiliates be a "direct link" to a current or former validated gang affiliate (§ 3378, subd. (c)(4)) required in these circumstances a "reciprocal (i.e., mutual or two-way) interaction between the two individuals forming the relationship." Having found insufficient evidence of such a reciprocal relationship, the Court of Appeal granted the writ and ordered the CDCR to expunge Cabrera's validation as an associate of the Mexican Mafia gang and to cease housing Cabrera in the SHU to the extent the assignment had been based on the gang validation. In light of its disposition, the Court of Appeal found it unnecessary to consider Cabrera's other challenges to the validation order.
We granted review to resolve a question of law concerning the deference owed to the CDCR in interpreting its own regulations governing the identification of inmates as prison-gang affiliates.
It is a " 'black letter' proposition" that there are two categories of administrative rules--quasi-legislative rules and interpretive rules--and that the distinction between them derives from their different legal foundations and ultimately from the constitutional doctrine of the separation of powers. (Yamaha Corp. of America v. State Bd. of Equalization (1998) 19 Cal.4th 1, 10 (Yamaha).) Quasi-legislative rules are those that the agency promulgates as part of the lawmaking power the Legislature has delegated to it, and are subject to "very limited" review. (Sara M. v. Superior Court (2005) 36 Cal.4th 998, 1012.) " 'The courts exercise limited review of legislative acts by administrative bodies out of deference to the separation of powers between the Legislature and the judiciary, to the legislative delegation of administrative authority to the agency, and to the presumed expertise of the agency within its scope of authority.' " (San Francisco Fire Fighters Local 798 v. City and County of San Francisco (2006) 38 Cal.4th 653, 667.) Rules that interpret a statute, on the other hand, receive less judicial deference. (Sara M., supra, 36 Cal.4th at p. 1012.)
The Legislature has "provided no specific guidance regarding how prisoners should be classified" (In re Jenkins (2010) 50 Cal.4th 1167, 1173), but has instead delegated lawmaking power to the CDCR to "prescribe and amend rules and regulations for the administration of the prisons." (Pen. Code, § 5058; see also id., § 5068.) "By enacting these statutes, '[t]he Legislature has given the [secretary] broad authority for the discipline and classification of persons confined in state prisons. [Citations.] This authority includes the mandate to promulgate regulations governing administration, classification, and discipline.'" (In re Jenkins, supra, 50 Cal.4th at p. 1173.)
Section 3378 (the regulation at issue here) is a quasi-legislative rule promulgated by the CDCR to identify and manage inmates with a prison-gang affiliation. Because the CDCR, like any agency granted this sort of substantive lawmaking power, is "truly 'making law,' [its] quasi-legislative rules have the dignity of statutes. When a court assesses the validity of such rules, the scope of its review is narrow. If satisfied that the rule in question lay within the lawmaking authority delegated by the Legislature, and that it is reasonably necessary to implement the purpose of the statute, judicial review is at an end." (Yamaha, supra, 19 Cal.4th at pp. 10-11.) "The substitution of the judgment of a court ...