California Code, Business and Professions Code - BPC § 5415

The director shall prescribe and enforce regulations for the erection and maintenance of advertising displays permitted by Sections 5226, 5405, and 5408 consistent with Section 131 of Title 23 of the United States Code and the national standards promulgated thereunder by the Secretary of Transportation; provided, that the director shall not prescribe regulations imposing stricter requirements for the size, spacing or lighting of advertising displays than are prescribed by Section 5408 and provided that the director shall not prescribe regulations to conform to changes in federal law or regulations made after November 8, 1967, without prior legislative approval.

Notwithstanding any other provisions of this chapter, no outdoor advertising shall be placed or maintained adjacent to any interstate highway or primary highway in violation of the national standards promulgated pursuant to subsections (c) and (f) of Section 131 of Title 23 of the United States Code, as such standards existed on November 8, 1967.