Serious talk about oil exports was last heard in Washington in the 1970s. With the Arab oil embargo a fresh memory and fears that domestic drilling had peaked, Congress instituted fuel-economy standards for cars, an energy-conservation program for consumer products, and the Strategic Petroleum Reserve, it also banned all exports of US oil except for small amounts to Canada. Four decades later that ban is threatening to put a damper on the US shale-oil boom. Either Congress or the president should find a way to reverse or at least temporarily suspend it.