Conservatives will probably be cheering today’s decision by the Supreme Court to allow the EPA to use cost-benefit analysis when deciding what constitutes a “best available control technology” in the Clean Water Act. I’m not so sure, however, that conservatives should be all that happy. Put aside the statutory dispute for a moment: Are we really comfortable with regulatory agencies having this much discretion when it comes to making law (in the form of regulation)?

The court’s reading of the CWA in this circumstance amounts to this: Congress said, “EPA, make power companies use the best damned emission control technologies that they can. I’ll leave it to you to decide what that means — use your discretion.” In short, it deputizes bureaucrats to play the role the Constitution vests in the legislature with no real intelligible principle to guide their lawmaking. That — I submit — is a bad idea (and, in my opinion, an unconstitutional idea) that will harm, not hurt, the conservative agenda in the long run.