There is a round of bans on imports of products containing the banned substances. Since that is largely non-discriminatory. Its the ban of imports of products made using the banned substances that do not contain the banned substances that is trickier under the WTO. The provisions for trade with non-signatories to the agreement is to try to ban the import, where feasible. The provision for trade with signatories is that each signatory that is unable to completely phase out use of the banned substance for domestic production bans the export of products made with the banned substance. And of course, there is nothing in the WTO to force any country to allow the export of any product.

So that would be deal - in exchange for being permitted market access to the EU for a range of products not presently agreed to in the WTO, in particular agricultural products, the signatories that do not have domestic CO2 regulation up to a certain standard agree to impose a carbon export tax on a range of products, include allowing a technical panel of the agreement set adjustments based on actual production methods in use in the country.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.