Cal. Pub. Res. Code § 5022.6

The department shall adopt standard design and detail for the marker and for the plaque which may be erected or raised at registered historical landmarks. The use of such marker or plaque shall be prescribed by rule adopted by the department. Any person who maliciously or for commercial purposes, or contrary to such rule, uses or allows to be used any reproduction or facsimile of such standard marker or plaque in any manner whatsoever is guilty of a misdemeanor.