Kalifornia has passed a lot of laws that have been eventually ruled unconstitutional. I think the law incolving SKSs was one of those.
I have heard of retroactive tax cuts, but I don’t remember a retraoactive tax increase. Remember the government can pass any law it wants to; it is up to the people to resist by challenging those laws in the courts. If normal channels fail, then there we must resort to . . . I dare not say.
Sorry, that bridge has already been crossed, under Clinton. They passed an Estate Tax increase retroactive to 1/1/93. It went to the USSC, which upheld it. How, I cannot fathom to this day (and I'm a lawyer).