Cal. Veh. Code § 11105.5
The department shall issue an independent driving instructor's license to permit instruction in any city with a population of less than 50,000, which does not have within it an established licensed driving school, to any person who meets the requirements of this chapter relating to instructor's and independent instructor's licenses, even though such person is not an employee of, or otherwise associated with or instructing through, a driving school, except that no independent driving instructor's license shall be issued to a person to instruct in counties with a population in excess of 400,000. In addition, an independent instructor must at all times be employed as an accredited teacher of automobile driver education or automobile driver training under the provisions of the Education Code.
Ca. Veh. Code § 11105.5