California Code, Business and Professions Code - BPC § 5403

(a) If within the right-of-way of any highway.

(b) If visible from any highway and simulating or imitating any directional, warning, danger or information sign permitted under the provisions of this chapter, or if likely to be mistaken for any permitted sign, or if intended or likely to be construed as giving warning to traffic, by, for example, the use of the words “stop” or “slow down.”

(c) If within any stream or drainage channel or below the floodwater level of any stream or drainage channel where the advertising display might be deluged by flood waters and swept under any highway structure crossing the stream or drainage channel or against the supports of the highway structure.

(d) If not maintained in safe condition.

(e) If visible from any highway and displaying any red or blinking or intermittent light likely to be mistaken for a warning or danger signal.

(f) If visible from any highway which is a part of the interstate or primary systems, and which is placed upon trees, or painted or drawn upon rocks or other natural features.

(g) If any illumination shall impair the vision of travelers on adjacent highways. Illuminations shall be considered vision impairing when its brilliance exceeds the values set forth in Section 21466.5 of the Vehicle Code.

(h) If visible from a state regulated highway displaying any flashing, intermittent, or moving light or lights.

(i) If, in order to enhance the display's visibility, the owner of the display or anyone acting on the owner's behalf removes, cuts, cuts down, injures, or destroys any tree, shrub, plant, or flower growing on property owned by the department that is visible from the highway without a permit issued pursuant to Section 670 of the Streets and Highways Code.