More than a dozen state attorneys general wrote to the head of the Environmental Protection Agency vowing a legal fight to block regulators from easing vehicle-emissions standards, the latest broadside in a battle over the Trump administration’s move to reopen a review of the regulations. New York Attorney General Eric Schneiderman and 12 other attorneys general sent a letter to EPA Administrator Scott Pruitt late Thursday, threatening to take the agency to court should U.S. officials relax the standards when the…