The issue is currently under consideration by the European Commission, which is drafting a green paper on which sectors should trade greenhouse gas emissions from 2013.
Transport is currently excluded from the EU emissions trading system, but it could be included from 2013 if administrative and monitoring problems can be overcome.
This could mean governments issuing CO2 permits to road users, which could be sold if a company reduced its CO2 emissions by – for example – switching to hybrids.
But last week the ECJ ruled that national governments had the right to withdraw such permits without compensation if they considered too many had been released.
Its ruling said: “The fact that the ex-post adjustments at issue are liable to deter operators from reducing their emission rates is not sufficient to call into question the adjustments’ legality.”
It backed a German government system which allows permits to be withdrawn in instances where a company slashed its emissions by more than 60%, compared with those emitted when first surveyed by the national permit authority.
The British Government has been especially keen that the commission considers including road transport in the EU emissions trading system, noting in a Department for Transport paper, emissions trading “could sit alongside other forms of direct intervention to reduce road transport CO2 emissions such as the use of biofuels, fuel efficiency, and eco-driving”.