CA has the worst gun laws in the country. Existing guns are grandfathered. New semi-auto rifles cannot have a magazine that can be removed w/o disassembling the gun. I thought I read somewhere that they were to confiscate existing magazines that hold more than 10 rounds, but I am not sure on that.
The existing one's have to be registered to be considered for that, otherwise you're a felon for having legally purchased a firearm that was completely legal when you bought it. They're registering even the firearms with the old "bullet buttons" as (their own self-created category), Assault Rifles.