I thought Hawaii was bad when it came to restrictions, but a buddy of mine in CA mentioned the following are banned by 2018 for rifles.

1) Protruding prongs for a flash suppressor (Mil not even allowed).  Muzzle break must be flush.
2) Can't be able to wrap thumb around rear pistol grip (need a plate that blocks this, and needs an ambi safety selector)
3) No front grips
4) Need a fixed stock (no adjustable)
5) Magazine must be welded in place or need to separate upper and lower to remove magazine.
6) Trying to pass prop63 that bans cross of state lines for shipment of ammo

Basically anything that makes the rifle look scary.

I didn't look  up these regulations, but just what he told me.  So unconfirmed exact regulation.

I hate the state of California on so many different levels...except the Dodgers. They get a pass, sort of 

In regard to weapon features, the only thing that changed during Gov. Brown's anti-gun bill passing in the summer was removing the "bullet button" exception that allowed you to maintain MSR features. Flash suppressor and thumbhole stocks have been banned since the 1999 law that broadened the 1989 Robert Roosi AWB to guns otherwise not mentioned in that previous law. The 1999 law covered any semiautomatic centerfire rifle with a detachable magazine and any of six "military-style" features: 1) a flash suppressor, 2) a grenade launcher or flare launcher, 3) a thumbhole stock, 4) a folding or telescoping stock, 5) a forward pistol grip, or 6) a pistol grip that protrudes conspicuously beneath the action of the weapon.