The U.S. energy industry can legally refine gasoline and diesel fuel for export, but for that market foreign consumers and U.S. consumers face the same constraints. If U.S. pipeline capacity and U.S. refining capacity are constrained, then it doesn’t matter if you’re refining the fuel for U.S. consumption or for export. All of the crude oil is using the same pipelines and refineries, regardless of where the fuel ends up being sold.