All trading bodies have rules - of course they do, or chaos would ensue. That is a red herring.
The UK is already part of the WTO. So is the EU.
hy would we limit ourselves to the EU when we could make agreements globally? We will still continue to trade with the EU and them with us. The terms will be different but most of the rest of the world is dealing under WTO regulations (including the EU.)
WIKI. "Only 12 countries are not WTO members. These nations do not wish to become members. They are Eritrea, Kiribati, Marshall Islands, Micronesia, Monaco, Nauru, North Korea, Palau, San Marino, Somalia, South Sudan, Turkmenistan, and Tuvalu. " 20 Apr 2018