The 5th circuit Court of appeals struck down the Trump bump stock ban today, but not on 2A grounds. The appellant said that a bump stock can’t be a machine gun because the law defines a machine gun as one that fires multiple times with a “single function of the trigger” and a bump stock causes the trigger to function multiple times.
The government argued that the key is the action of the shooter, who only has to do one thing, the shooter’s trigger finger isn’t doing anything other than sitting still.
That would be a great argument if the law said a machine gun is one that fires multiple shots with a single action taken by the shooter, but that isn’t what the law says. It specifically says “single function of the trigger.”