When special interest groups want goodies from Congress, they’ll often cloak their pleas in the garb of “national security.” So nearly a century ago, Congress passed the Merchant Marine Act of 1920. And so it is today, as proponents of that law—which costs the U.S. economy $200 million a year—try to keep it in place. This protectionist measure, better known as the Jones Act, requires that all cargo shipped between U.S. ports be carried by U.S.-built, U.S.-crewed, U.S.-owned ships.