Many years ago, Cass Sunstein wrote a paper called Cost-Benefit Default Principles, which argued that regulatory agencies are free to use cost-benefit analysis when statutes are ambiguous. EPA v. EME Homer City Generation seems to confirm this thesis, but arguably goes beyond it, at least if you accept Scalia’s argument that the text is clear and clearly forbids EPA to take account of cost. The case may instead stand for the existence of a stronger cost-benefit presumption that entitles a regulator to use cost-benefit analysis unless Congress explicitly forbids it to. Thus, a “gap” is not needed. The justification would be that Congress ought to direct regulators to take account of costs, perhaps that cost-benefit analysis is a quasi-constitutional commitment, so statutes should be “interpreted” as much as possible to avoid conflicting with this commitment.
Cost-benefit analysis as a constitutional commitment, quasi- or other? Could there be a justification for such a claim? Possibly. Consider the longstanding worry that the New Deal regulatory state gave excessive discretion to regulators, and the defunct efforts to rein them in with the nondelegation doctrine. Scalia’s insistence on deferring to the text, however loopy the text might be, is one possible response, but a more realistic one, I think, is rather to confine regulators’ discretion by insisting that they use cost-benefit analysis. The Court did not go quite so far, but took a step in that direction.