Cal. Welfare and Institutions Code § 14059.5

(a) For individuals 21 years of age or older, a service is “medically necessary” or a “medical necessity” when it is reasonable and necessary to protect life, to prevent significant illness or significant disability, or to alleviate severe pain. (b) (1) For individuals under 21 years of age, a service is “medically necessary” or a “medical necessity” if the service meets the standards set forth in Section 1396d(r)(5) of Title 42 of the United States Code. (2) The department and its contractors shall update any model evidence of coverage documents, beneficiary handbooks, and related material to ensure the medical necessity standard for coverage for individuals under 21 years of age is accurately reflected in all materials. (3) Notwithstanding Chapter 3.5 (commencing with Section 11340) of Part 1 of Division 3 of Title 2 of the Government Code, the department, without taking any further regulatory action, shall implement, interpret, and make specific this subdivision by means of all-county letters, plan letters, plan provider bulletins, manuals, plan contract amendments, or similar instructions until regulations are revised or adopted. (4) By July 1, 2022, the department shall revise or adopt regulations in accordance with the requirements of Chapter 3.5 (commencing with Section 11340) of Part 1 of Division 3 of Title 2 of the Government Code. This paragraph shall not apply to a Medi-Cal behavioral health delivery system, as defined in subdivision (i) of Section 14184.101. (c) This section shall not be construed to limit the application of subdivisions (a) and (b) of Section 51184 of Title 22 of the California Code of Regulations. (d) Medical necessity for covered benefits provided in a Medi-Cal behavioral health delivery system, as defined in subdivision (i) of Section 14184.101, shall also be governed in accordance with Section 14184.402.