The Justice Department on Tuesday unsealed charges, and sought extradition, of a Brit who did day-trading in futures contracts from his London home. The Commodity Futures Trading Commission also filed civil charges against Navinder Singh Sarao and his company. Sarao was arrested in the U.K. over the charges relating to manipulation. While the government has alleged manipulation on at least ten different occasions, it is the activity on May 6, 2010, that will draw the most attention. The U.S. government says Sarao was engaged in what’s called layering, which involves making multiple, bogus orders that are quickly cancelled to trick...