California will take them to court and/or block them from doing business in the state, have various ways to penalize them, etc. California is big enough that many will want to play game with them and having a state as powerful as California on board will get other states to jump on board and pass their own legislation and take up the same tactics with non-complying companies. Once it gets enough traction at the state level, the fed will step in because this will affect interstate commerce and that is federal jurisdiction. This is how state sovereignty works, it is not that states can do as they please, they can only do it up until the point it affects other states or crosses the line with federal law.