California Code, Health and Safety Code - HSC § 11362.712

(a) Commencing on January 1, 2018, a qualified patient must possess a physician's recommendation that complies with Article 25 (commencing with Section 2525) of Chapter 5 of Division 2 of the Business and Professions Code. Failure to comply with this requirement shall not, however, affect any of the protections provided to patients or their primary caregivers by Section 11362.5.

(b) A county health department or the county's designee shall develop protocols to ensure that, commencing upon January 1, 2018, all identification cards issued pursuant to Section 11362.71 are supported by a physician's recommendation that complies with Article 25 (commencing with Section 2525) of Chapter 5 of Division 2 of the Business and Professions Code.