The opinion is here.

Health and Safety Code section 11362.77,1 which is part of the Medical Marijuana Program (MMP) (§ 11362.7 et seq.), prescribes a specific amount of marijuana that a “qualified patient” may possess or cultivate. We granted review to determine whether this aspect of section 11362.77 is invalid under California Constitution, article II, section 10, subdivision ©, insofar as it amends, without approval of the electorate, the Compassionate Use Act (CUA) (§ 11362.5), an initiative measure adopted by the voters as Proposition 215 in 1996.

We conclude, consistently with the decision of the Court of Appeal below (and with the position of both parties in the present litigation), that insofar as section 11362.77 burdens a defense under the CUA to a criminal charge of possessing or cultivating marijuana, it impermissibly amends the CUA and in that respect is invalid under article II, section 10, subdivision ©. We also conclude, consistently with the views of both parties in the present litigation, that the Court of Appeal erred in concluding that section 11362.77 must be severed from the MMP and hence voided.

....Whether or not a person entitled to register under the MMP elects to do so, that individual, so long as he or she meets the definition of a patient or primary caregiver under the CUA, retains all the rights afforded by the CUA. Thus, such a person may assert, as a defense in court, that he or she possessed or cultivated an amount of marijuana reasonably related to meet his or her current medical needs (see Trippet, supra, 56 Cal.App.4th 1532, 1549), without reference to the specific quanitative limitations specified by the MMP.

....We conclude as follows: To the extent section 11362.77 (together with its quantitative limitations) impermissibly amends the CUA by burdening a defense that would be available pursuant to that initiative statute, section 11362.77 is invalid under California Constitution article II, section 10, subdivision ©.