Or require that imports buy CO2 permits equivalent to their average per domestic unit of currency CO2 emissions unless it can be proven that the full CO2 emission impact justifies a smaller permit, or that a meaningful cap is in place.

China, the US, South Africa, Russia, India and Australia will kick in the WTO, so maybe first some EU producer needs to sue that allowing imports in without buying their permits is a discriminatory trade policy.

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