To handle the matter technically Utah would need a "great firewall of Utah" and a legislative mandate that all ISPs route thru it. Somehow they'd have to factor-in signals from cellular sites neighboring states and satellites.
The inability to immediately and perfectly eliminate a behavior is not a good enough reason to be against any attempt to eliminate that behavior.
So if you are legally required to block all VPN users and then fail to actually block all VPN users what is stopping you from being punished for not complying with the law?
Under Utah's law as written, a private business has to assume any single IP address could be operating a VPN/proxy.
With cross tunneling all your normal traffic would go through your ISP usually and just your porn traffic goes through the VPN. Unless it's a major provider, as far as your ISP is concerned you're just connecting to someone's private server occasionally
Since when do you have to pull permits to put a server on the web?