Change of rules & regulations after accepting faculty contract offer
This is an unfortunate situation were nobody really is to blame. You can't expect the university to warn you about a law that wasn't even in place yet, and the university cannot objectively be mad at you for reneging when your contractual situation significantly changed, even if it is due to outside factors. Of course the important word in the above statement is "objectively" - nobody can ensure you that the people that wanted to hire you will also see it like that, and that you won't burn any bridges.


  Is it too late to turn down the academic offer? I have accepted it on e-mail but I haven't signed anything yet and haven't even seen the contract. If yes, what is the best way to do this?


As long as you have not signed anything you are always in the right to back out. The best way to do it would be to warn them that this new development significantly changes your view on their offer, even if they are of course not to blame. I would stay clear of any accusations that they failed to inform you in advance. Note that this also gives them the option to up their offer, which would presumably change your mind back again.

You should do it in the same form as you tentatively accepted the offer before - if you communicated that you would take the offer via email, send them a brief follow-up that you changed your mind, and why.


  Is anything similar happening to any other country and how do academics people deal with it?


I am not aware of any concrete cases, but presumably when Brexit broke there had to be cases of academics changing their mind about moving to the UK.