by Cass Sunstein

One of the most interesting questions raised by today's decision is the likely aftermath. In a nutshell, the EPA said that it lacked the legal authority to regulate greenhouse gases from motor vehicles, and also said that it would decline to regulate greenhouse gases even if it had such authority. The Court ruled (1) that the EPA had the authority to regulate greenhouse gases and (2) that it did not adequately explain why it declined to do so. Hence the Court remanded the case to the EPA, to explain itself in terms that are consistent with the Clean Air Act. On remand, we can easily imagine two possibilities. (a) The EPA might try to give a better explanation of why it does not seek to regulate greenhouse gas emissions from motor vehicles. If it takes this course, and hence declines to act, it will almost certainly face a legal challenge. (b) The EPA might conclude that it will indeed regulate greenhouse gases from motor vehicles. If so, it will start a (time-consuming) rulemaking procedure. If it does eventually attempt to regulate greenhouse gases, its decision will likely be challenged in court. A few years ago, (a) would have been far more likely, and it certainly would not be a big surprise. But with the current political and scientific environment, (b) cannot be ruled out; (a) would meet not only a legal challenge but a great deal of public skepticism. Note, however, that any response by the EPA might take a fairly long time. It may well be that if the agency goes route (b), any real action will have to be taken by the next president. For the short term, it would be useful to see if anyone in the White House, or the EPA, gives a signal about whether (a) or (b), or some (c), is more likely.