Volkswagen’s behavior may have been bad, but did it ever make sense to mandate that passenger cars, after 2008, be restricted to 0.07 grams of nitrogen oxide output per mile?

This target of 0.07 grams is already about a 90% reduction from the NOX output of the average car on the road today, according to the EPA. It represents about 1/40th the output of the average full-size pickup (gasoline or diesel), of which more than 10 million are on the road.

No...