America's shale gas boom is so promising that it has some people discombobulated—including, naturally, our politicians. The same folks who complain about America's trade deficit now want the U.S. government to ban the export of liquefied natural gas (LNG). This is one way to ruin what has been a very rare piece of good U.S. economic news.

Unlike oil, which is a global commodity sold at a global price, the world natural gas market is fragmented by limits on supply. Gas has to be liquefied before it can be loaded on ships and transported. But with the natural gas price ...