In-home ownership of an auto is legal in Calif, regardless of length. It's street-carry that's limited to sub-2".
Of course, when BUYING an auto you run into all the usual Fed problems/BS.
The only knives you can't own in Calif are those that are disguised as something else (lipstick container, shotgun shell, etc) and cane-swords. Here, I'll quote the exact bit on "ownership bans":
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12020. (a) Any person in this state who does any of the following is punishable by imprisonment in a county jail not exceeding one year or in the state prison:
(1) Manufactures or causes to be manufactured, imports into the state, keeps for sale, or offers or exposes for sale, or who gives, lends, or possesses any cane gun or wallet gun, any undetectable firearm, any firearm which is not immediately recognizable as a firearm, any camouflaging firearm container, any ammunition which
contains or consists of any flechette dart, any bullet containing or carrying an explosive agent, any ballistic knife, any multiburst trigger activator, any nunchaku, any short-barreled shotgun, any short-barreled rifle, any metal knuckles, any belt buckle knife, any leaded cane, any zip gun, any shuriken, any unconventional pistol, any lipstick case knife, any cane sword, any shobi-zue, any air gauge knife, any writing pen knife, any metal military practice
handgrenade or metal replica handgrenade, or any instrument or weapon of the kind commonly known as a blackjack, slungshot, billy, sandclub, sap, or sandbag.
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Now, so far as I'm aware, *nobody* knows what the hell a "shobi-zue" is. It'd be friggin' hilarious if it wasn't so sad because you just know that at SOME time, a jerk of a cop tried to convince some poor kid that his SAK or whatever is a "shobi-zue" just for harassment purposes.
Anyways...all the knives that are illegal to own are in that list. Autos ain't there.
There's also supposedly a basic rule somewhere (or maybe just "street lore among cops") that people missing an arm shouldn't get busted for switchblade carry.
Jim