California Code, Business and Professions Code - BPC § 5050

(a) Except as provided in subdivision (b) of this section, in subdivision (a) of Section 5054, and in Section 5096.12, no person shall engage in the practice of public accountancy in this state unless the person is the holder of a valid permit to practice public accountancy issued by the board or a holder of a practice privilege pursuant to Article 5.1 (commencing with Section 5096).

(b) Nothing in this chapter shall prohibit a person who holds a valid and current license, registration, certificate, permit, or other authority to practice public accountancy from a foreign country, and lawfully practicing therein, from temporarily engaging in the practice of public accountancy in this state incident to an engagement in that country, provided that: