California Code, Business and Professions Code - BPC § 2060

Nothing in this chapter applies to any practitioner located outside this state, when in actual consultation, whether within this state or across state lines, with a licensed practitioner of this state, or when an invited guest of the California Medical Association or the California Podiatric Medical Association, or one of their component county societies, or of an approved medical or podiatric medical school or college for the sole purpose of engaging in professional education through lectures, clinics, or demonstrations, if he or she is, at the time of the consultation, lecture, or demonstration a licensed physician and surgeon or a licensed doctor of podiatric medicine in the state or country in which he or she resides.  This practitioner shall not open an office, appoint a place to meet patients, receive calls from patients within the limits of this state, give orders, or have ultimate authority over the care or primary diagnosis of a patient who is located within this state.