I'm in california, i probably know it better than anyone. hell i can't put a cold air intake on my truck unless it's "CARB approved" (california air resource board). if i have a non CARB approved intake on there it'll fail smog just because its on there (visual inspection) if i get pulled over and the cop thinks my truck is modified he can inspect it, if i don't let him inspect it he can and probably will impound it. if he see's that i have a non CARB approved intake i get a ticket at best or get put in state ref at worst. if it gets state reffed i have to convert the entire vehicle (not just the modified/offending parts) back to factory stock/OEM and have it inspected. can't drive it on the road until it passes inspection. in some cases i can't even sell it until it passes inspection.
made even more fun by LA county and the 4 surrounding county's having something referred to as the "street race task force" which is supposed to help combat street racing and street takeovers. but isn't. so we have an entire taskforce looking for modified vehicles at 5 in the afternoon, you know, during prime street racing hours

its basically a way to harass anyone with a modified car. if you so much as have aftermarket wheels you can be pulled over and have your car inspected. never mind that street racers don't come out until pushing midnight and in unpopulated area's. and street takeovers typically don't happen until after 9pm and typically use stock vehicles.
then we also have to deal with CARB now going after classic car owners. put an LS in your 57 Chevy. yeah, they'll come after you and make you smog it every 2 years like a new car. so you'll have to have all the emissions equipment associated with that LS on your 57 Chevy or you'll fail the smog test and won't be able to register the car. needless to say people are starting to leave hoods down at car shows
meanwhile i live next to an airport full of small privately owned aircraft that largely get flown for recreation, that burns leaded fuel. and it's all largely unregulated.