Some of President Obama's unilateral actions may raise legitimate concerns, even for those who believe this Congress is noxiously unproductive. But his demand that cars and trucks use less fuel raises no such question. The president's plan rests on a rock-solid legal foundation. It's also the right thing to do while lawmakers dither on climate change.
Last week Mr. Obama said his administration would use the powers it has under various laws to press for tougher efficiency standards for heavy trucks. A relatively small number of these massive vehicles produce about a quarter of the transportation sector's greenhouse gas emissions, according to the White House.
That doesn't mean truckers are particular climate villains; the country depends on them to bring 70 percent of the nation's freight tonnage to market, and big trailers use a lot of fuel. But if they can reduce fuel consumption and emissions at little or no cost, they should.