US President Donald Trump has ordered a Justice Department investigation into major oil companies, accusing them of keeping gasoline prices artificially high despite a recent fall in crude oil prices. The move reflects frustration that fuel prices have not dropped as quickly as he had promised after tensions with Iran eased and tanker traffic resumed through the Strait of Hormuz.

The president complained that prices at the pump haven’t dropped sharply enough despite a sharp slump in crude prices since the Iran peace deal went into effect.

The president seems surprised that gas prices haven’t magically returned to normal.