The Obama-era rules to be reconsidered were designed to address global warming and put the United States at the forefront of global car-efficiency regulation. The Trump administration is expected to launch an effort in coming days to weaken greenhouse gas emissions and fuel economy standards for automobiles, handing a victory to car manufacturers and giving them ammunition to potentially roll back industry standards worldwide. The move — which undercuts one of President Barack Obama’s signature efforts to fight climate change — would also propel the Trump administration toward a courtroom clash with California, which has vowed to stick with the stricter rules even if Washington rolls back federal standards. That fight could end up creating one set of rules for cars sold in California and the 12 states that follow its lead, and weaker rules for the rest of the states, in effect splitting the nation into two markets. […]