What do you mean? You would continue to use the copper infrastructure, but fibre connections in to it would be regulated. A serious ISP could still do them, but one that just allows random people to make an account wouldn't be allowed to connect.

So, Verizon could peer their copper network with Sprint's copper network and connect them over fibre, but if Verizon would accept fibre peering with random VoIP providers Sprint wouldn't peer with them because they would be liable for fines.