Since CO2 emissions are related to fuel consumption, the rules would have required an increase in fuel efficiency to 43 mpg by 2016. The car companies, as expected, said they couldn't do this, just as they have always done in the past. Of course, car makers have complained about every regulation that has gone into effect over the past four decades before ultimately meeting them. As a result, the judge decided that the arguments were meaningless. The automakers may still get what they want if the EPA declines to grant California a waiver for the new rules, but the federal courts don't seem to be inclined to listen so far.
[Source: Detroit Free Press]