The EPA will. (And then the Obama administration will be on the hook for what carbon regulation does to the U.S. economy.)

The editors of the Washington Post repeat the familiar threat. An excerpt:

The Clean Air Act, in other words, is breathtakingly unsuited to the great task of battling global warming. It would provide no economy-wide and declining cap on carbon, no market signal to industry or clean-energy investors that could spark innovation and greater efficiencies. There would be a thicket of red tape and regulations but nowhere near the reduction in greenhouse gas emissions of the Waxman-Markey bill, let alone those called for by the Intergovernmental Panel on Climate Change.
The specter of EPA regulation is supposed to scare Congress into more rational action. Yet if Congress does not act, it’s likely that the EPA will. It won’t be pretty.