AP Photo

His department has to make a recommendation to the President, who is free to ignore or accept it. In one ear, he will hear the national security arguments for Keystone and the negative impact its rejection would have on relations with the Harper government; in the other, he will hear echoes of his own words as a senator. (He was non-committal on Friday after meeting Foreign Affairs Minister John Baird in Washington.) Ultimately, Mr. Obama will decide. He has identified climate change as a major challenge and spoke in that inaugural speech about taking the “path toward sustainable energy sources,” a path that, by definition, would exclude or minimize the use of fossil fuels. He once promised a cap-and-trade system for emissions, but that idea died in Congress even when the...