The Supreme Court today granted cert for (agreed to hear) appeals from a set of consolidated cases decided by the DC Circuit last year. In those cases, the lower court had preserved EPA's authority to regulate greenhouse gases under the Clean Air Act. Ann Carlson of UCLA has an excellent summary on Legal Planet - it's worth a read whether you're familiar with the background or not. The short version is that only one narrow issue will be reconsidered by the Supreme Court - the lower court's decisions on all other issues (all of them decided in EPA's favor) will stand. This preservation of the lower court's rulings is a major decision by the Court, and will likely get limited press coverage since it lacks the buildup and theater of a full cert grant. In fact, I predict there will be some coverage suggesting that by granting cert, even on the one narrow question, the Court plans to question EPA's entire GHG regulatory program. That's not the case.
Today's decision means that the most important parts of that program will proceed. Critics viewed the cert petition as an opportunity for the Court to reconsider it's Massachusetts v. EPA decision enabling Clean Air Act regulation of GHGs in light of what they view as a "train wreck" of regulations it has (and will) spawn, echoing warnings in Justice Scalia's Massachusetts dissent. The court didn't take that opportunity, making it more clear than ever that Massachusetts is settled law. If there is to be a change in the broad scope of EPA's authority over GHGs, it will have to come from Congress.
I only differ from Carlson's reading of the cert grant in one small respect. She implies that the Court will review two parts of EPA's approach - both the "timing" and "tailoring" rules. The former determines whether regulating GHGs from vehicles requires EPA to consider them in its new source review process, and the latter restricts GHG-driven reviews to large emitters, at least initially. My reading is that the cert grant only covers the legality of the timing rule, not the tailoring rule. This is important since I (and others) had viewed the tailoring rule as the most legally questionable part of EPA's approach. And indeed I'm not ready to conclude that it is completely safe - the challenge in the lower court was rejected on standing grounds, so a different plaintiff may be more successful. But the tailoring rule's survival at the DC Circuit and SCOTUS is a major victory for EPA.
It is true, however, that if SCOTUS rejects the timing rule, then the tailoring rule doesn't matter much since EPA wouldn't be able to regulate GHGs through new source review at all. That's probably what Carlson means when she suggests both rules are before the Court. But I think it's important to point out that only the threshold timing rule appears to be at stake.
In general, the limited cert grant is great news for EPA. Whether it is great news more generally (i.e. for the economy and the environment) depends on how EPA uses the Clean Air Act tools available to it. I'm optimistic - partly because the President specifically directed EPA to regulate flexibility in his June speech that released the agency from it's election-and confirmation-hearing-driven leash. But also because the alternative, in the current political climate, is no action on climate at all.
UPDATE: Jonathan Adler also has thoughts at the Volokh Conspiracy. His post (and amicus brief) is worth a read. I agree with him that the question on which EPA granted cert does allow it to consider some of the allegedly absurd results of Massachusetts - specifically the implications of vehicle GHG regulations (the issue in Mass) for new source review. But I don't think NSR is very important. Even if GHG NSR isn't compelled (or even allowed) by the statute, new source performance standards can and will still limit new source GHG emissions (or even effectively ban construction of new coal plants). The most important GHG regulations under the Act, standards for existing sources, will be similarly unaffected by any outcome of this case. These are the results (absurd or not) that critics of EPA GHG regulation should really be worried about. NSR is a sideshow.