Johnson makes the point that this is a federal jurisdictional issue because greenhouse gases are a global pollutant.  This makes logical sense, but I'm not sure it makes legal sense.  There is a rather lengthy precedent for the feds not getting involved in state electricity policy - from setting prices on wholesale rates to setting grid interconnection standards - on the argument that the federalist system allows federal oversight only where interstate commerce is involved, and the transaction between a utility and a local generator is an single state transaction.  Many have argued (unsuccessfully) that the interconnected nature of our grid, lack of electron-level knowledge about the locations of state boundaries and the trans-state impacts of generation choices (including, but not limited to AGW) mandate federal oversight, but these arguments have consistently lost to the states-rights crowd.

My experience is that this federal-level punt on electricity policy has been massively costly, and explains why there is such a huge gap in energy efficiency between the states, in spite of broad agreement about what needs to be done.  (And why the most prehistoric states are those in the southeast, where states-rights arguments carry particular resonance.)  But if those arguments are valid and precedential, they would presumably apply equally to the transaction between a guy and his auto-dealer, no?  Perhaps a lawyer out there in the Grist-i-verse can chime in?