They will but that doesn't happen overnight. Somebody in CA will have to take it to court and foster it through the appeals process. It will likely be some state pro-gun organization and they will fight it to the highest court where they will claim victory.
A state can't write laws against a federal law or the Constitution unless they withdraw from the union and become their own country. Liberals are like 7 year olds. They are very childish and throw fits when they don't get their way. Newsom is making a bigger idiot out of himself than he was already known for