The story is here. It is not surprising that the Supreme Court did not accept the petition to review the judgment of the US Court of Appeals for the D.C. Circuit. With rare exception, the D.C. Circuit is the supreme court of federal administrative law; the actual Supreme Court gives its decisions great (though not unlimited) deference.
However, I would be surprised if at least a couple of the justices (perhaps Scalia and Thomas) were not eager to overturn the EPA's "Tailoring Rule" (on which see here and here).