Cal. Mil. & Vet. Code § 1650

Any individual, partnership, association, corporation, municipal corporation, or the State or any of its political subdivisions engaged in, or preparing to engage in, defense preparation, whose property, except where it fronts on water or where there are entrances for railway cars, vehicles, persons, or things, is enclosed, may post around its property at each gate, entrance, dock, or railway entrance and every 100 feet of water front a sign reading “no entry without permission.”