California Code, Penal Code - PEN § 556.2

Sections 556 and 556.1 do not prevent the posting of any notice required by law or order of any court, to be posted, nor the posting or placing of any notice, particularly pertaining to the grounds or premises upon which the notice is so posted or placed, nor the posting or placing of any notice, sign, or device used exclusively for giving public notice of the name, direction or condition of any highway, street, lane, road or alley.