How would you enforce a ban on taxis ? you call and see who shows up amd fine them. Same here just fine people when they send IP through known VPNs. Keep looking for VPN IPs... that's it. Very easy, very unpopular.

Probably batch banning IPs for non compliant providers - I did read that Mullvad are already able to get around that, so no issue. A VPS with my own vpn software installed would do the trick, just as easily.