From Consumer Wiki
The California Department of Transportation (CALTRANS) regulates outdoor advertising displays adjacent to any interstate highway or primary highway. It is also considered a part of the business and marketing function of the national economy and as such should be allowed to exist subject to reasonable controls in the public interest. Billboards are also subject to local city or county zoning ordinances.
Division of Traffic Operations
Outdoor Advertising Program
P.O. Box 942874, MS-36
Sacramento, CA 94274-0001
Complaints about inappropriate billboard material are handled by the United States Government Federal Trade Commission (FTC).
901 Market Street Suite 570
San Francisco, CA 94103
10877 Wilshire Blvd., Suite 700
Los Angeles, CA 90024
Other referrals: Division 3, Chapter 2, Article 1 of the Business and Professions Code and the California Administrative Code, Title 4, Chapter 6, Subchapters 1 through 5