California Code, Business and Professions Code - BPC § 16300

(a) Notwithstanding any other provision of this part, Chapter 1.5 (commencing with Section 7284) of Part 1.7 of Division 2 of the Revenue and Taxation Code, or Chapter 3 (commencing with Section 37100) of Part 2 of Division 3 of Title 4 of the Government Code, no city, including a charter city, city and county, or county may require an employee to obtain a business license or home business occupation permit for, or impose a business tax or registration fee based on income earned for services performed for an employer by the employee in an employment relationship as determined by reference to the common law factors reflected in rulings or guidelines used by either the Internal Revenue Service or the Franchise Tax Board.  When there is a dispute between a city, city and county, or county and a taxpayer, the manner in which a taxpayer reports or reported income to the Franchise Tax Board or the Internal Revenue Service shall create a presumption regarding whether the taxpayer performed services for an employer as an employee, or operated a business entity.  For purposes of this section, “income” includes income paid currently or deferred and income that is fixed or contingent.

(b) Nothing in this section shall be interpreted to limit the authority of a city, city and county, or county to adopt and enforce zoning, health and safety ordinances, or regulations that define and limit activities that are permissible within its jurisdiction for the purposes of health, safety, welfare, and the provisions of applicable noise ordinances.