While this proposed California law is unlikely to be Constitutional, there are federal laws that prevent people from simply leaving the country and taking all their money with them to avoid taxes. You can try, and with good lawyers and accountants, you can certainly shelter a lot of it, but in the end you can't avoid tax liability just by leaving. Plenty of uberrich get away with it, but it's still not legal. You can't even completely avoid it by renouncing your citizenship if you're a dual national; there's still a liability.
I know that the uberrich get away with dodging taxes all the time, but there are potentially high costs, like having your assets confiscated, or having to hide out in your island fortress and never return to the US lest you end up in prison.
I know that the uberrich get away with dodging taxes all the time, but there are potentially high costs, like having your assets confiscated, or having to hide out in your island fortress and never return to the US lest you end up in prison.