May 19 was a perfect day for a White House photo op. The sun was out, the Rose Garden was full, and everyone was smiling, even the CEOs of several automakers — which was ironic, because they were there to sign a suicide pact.

President Obama was unveiling, in his words, a “historic agreement” — a “harbinger of a change in the way business is done in Washington.” The federal government’s fuel-economy standards were being ratcheted up yet again, to 39 mpg for cars and 30 mpg for SUVs and other light trucks by 2016. That is one huge increase over …