The possible US diesel export ban comes at the worst possible moment for an already badly strained global fuel market. Diesel prices are at or near records as the Iran war disrupts Middle Eastern supplies, Ukrainian attacks have damaged Russian refineries and China is holding back fuel exports. The United States has been one of the few major suppliers filling the resulting gap, especially in Europe.
Cutting off that supply would not simply redirect American diesel to American consumers. It would remove a crucial pool of barrels from a global market that is already short of them, pushing up the cost of moving goods, producing food and running machinery far beyond the United States.