Montana and five other states say resident Barack Obama overstepped his power by rejecting the Keystone XL pipeline, whose developers are now suing four presidential cabinet members. The states along the pipeline’s route filed a friend-of-the-court brief this week arguing that Congress, not the executive, has the right to regulate interstate and international commerce. The pipeline, which would have crossed the Canadian border, was being developed by TransCanada, which is now suing the government. Because of the resident’s representations to the rest of the world that America would lead in reducing its carbon footprint, that that was the sole reason...