Cal. Bus. & Prof. Code § 5412
Notwithstanding any other provision of this chapter, no advertising display which was lawfully erected anywhere within this state shall be compelled to be removed, nor shall its customary maintenance or use be limited, whether or not the removal or limitation is pursuant to or because of this chapter or any other law, ordinance, or regulation of any governmental entity, without payment of compensation, as defined in the Eminent Domain Law (Title 7 (commencing with Section 1230.010) of Part 3 of the Code of Civil Procedure), except as provided in Sections 5412.1, 5412.2, and 5412.3. The compensation shall be paid to the owner or owners of the advertising display and the owner or owners of the land upon which the display is located.
This section applies to all displays which were lawfully erected in compliance with state laws and local ordinances in effect when the displays were erected if the displays were in existence on November 6, 1978, or lawfully erected after November 6, 1978, regardless of whether the displays have become nonconforming or have been provided an amortization period. This section does not apply to on-premise displays as specified in Section 5272 or to displays which are relocated by mutual agreement between the display owner and the local entity.
"Relocation," as used in this section, includes removal of a display and construction of a new display to substitute for the display removed.
It is a policy of this state to encourage local entities and display owners to enter into relocation agreements which allow local entities to continue development in a planned manner without expenditure of public funds while allowing the continued maintenance of private investment and a medium of public communication. Cities, counties, cities and counties, and all other local entities are specifically empowered to enter into relocation agreements on whatever terms are agreeable to the display owner and the city, county, city and county, or other local entity, and to adopt ordinances or resolutions providing for relocation of displays.
Ca. Bus. and Prof'l. Code § 5412