California does not have one law forbidding knives with blades over a certain length. California prohibits certain knives, and in two situations it defines prohibited knives by the length of the knife blade. Any knife that is not specifically prohibited in the statues is legal to own and carry in California.
Types of Prohibitions
California has two kinds of laws applying to knives. There are some knives that cannot be possessed or carried in public places, but can be possessed in private places like a home or out in nature. They may also be carried in inaccessible places like the trunk of a car. Other knives are categorized as dangerous weapons. It is a crime to possess dangerous weapons anywhere in California.
Under California law, switchblade knives with a blade of 2 inches or longer cannot legally be possessed in a public place or inside the driving area of a motor vehicle. The definition of a switchblade knife includes any kind of a folding knife that can be opened using an automatic opening mechanism of some kind. The statute, California Penal Code section 653k, lists some examples of this kind of a mechanism, such as a spring blade, gravity blade, or snap-blade. If you can open the knife with one hand by putting pressure on just the blade, but do not use any other mechanism, the knife is exempted from the statute as long as there is some mechanism to create resistance to opening the knife.
Belt Buckle Knives
Belt buckles that have built-in knives with blades that are 2 1/2 inches or longer are considered dangerous weapons in California and may not be possessed. The applicable statute is California Penal Code section 12020.
Possessing a switchblade knife with a blade of 2 inches or longer in a public place is a misdemeanor under California Penal Code section 653k. It is also a misdemeanor to sell, display for sale, transfer, loan, or give such a knife to another person in California. To make, import, sell, offer for sale, give, loan, or possess a dangerous weapon as defined under California Penal Code section 12020 is punishable by up to one year imprisonment.