A wealth tax is not a retroactive law, nor something that targets an individual person. It's a "general law" in your parlance. Think about it.
> If you pass a general law (which could very well have reasonable objections), people have to have a chance to leave.
I don't think so. By what legal authority is that required?
> "I'm passing this law that is effective the exact millisecond I sign it, tough shit if you don't like it" is tyranny and despotism. But based on your comment I think you know that.
No, it's not, and don't be ridiculous. When they passed laws against date-rape, would you have judged it "tyranny and despotism" unless the law was delayed to give the date-rapers time to finish up the date-rapes they'd planned?
There's no justice in giving the wealthy the maximum opportunity to pick and choose the laws that apply to them.