Rather than an explicit federal ban on machine guns, the law was designed to tax Tommy Guns out of existence. It required finger printing, licensing and paying a $200 tax to purchase machine guns and sawed-off shotguns, famously used by Clyde Barrow and Bonnie Parker. That hefty tax, the equivalent of about $3,800 in today’s dollars, was out of reach for most people at a time when the average annual income was about $1,780.

Attorney General Cummings told Congress nobody expected gangsters to register their weapons, but anyone caught with an unlicensed weapon would go to prison for tax evasion just as Chicago gangster Al Capone had two years earlier. By 1937, federal officials reported the sale of submachine guns in the U.S. had nearly ceased. In 1939, the U.S. Supreme Court ruled the law constitutional. The law so effectively ended the spread and use of submachine guns the federal government didn’t get around to actually banning civilian ownership until 1986.

Then 25 years ago under Democratic President Bill Clinton Congress banned assault weapons and high-capacity magazines after two mass murders in California. The ban lasted a decade until Republicans controlling the Senate refused to vote on renewal in 2004. Republican Senators defeated another renewal attempt after the 2012 Christmastime mass murder of 20 first graders and six adults at Sandy Hook Elementary School in Newtown, Conn.