The Obama administration has always had a backup plan in case Congress failed to pass a broad climate change bill. The Environmental Protection Agency would use its Clean Air Act authority to regulate greenhouse gases. Regulation, or the threat of it, would goad Congress to act or provide a backstop if it did not.

The House passed a bill last year seeking an economywide cap on emissions, but there has been no progress in the Senate. Now some senators seem determined to undercut the E.P.A.’s regulatory authority. These include not only Republicans who panic at any regulation, but also Democrats who say they worry about climate change but insist that the executive branch stand aside until Congress gets around to dealing with it.

The most destructive idea is a...