Fish and Game Code § 2018
CHAPTER 1. Taking and Possessing in General
It is unlawful to post any sign indicating an area is a state or federal refuge unless it is established by state or federal law, or to post any sign prohibiting trespass or hunting on any land unless authorized by the owner or the person in lawful possession of such lands.
It is unlawful for any person to maliciously tear down, mutilate, or destroy any sign, signboard or other notice forbidding hunting or trespass on land.