Taxes levied Interstate traffic and manufacturing licensing Machine gun ban

You gotta watch TRex Labs four part video series about the history of the ATF. It's a great explaination of the history of the NFA and the lives it has ruined.

Too many to name. The inability to easily purchase machine guns and suppressors is the big one. You can still get these items, but you have to pay a $200 extortion fee and submit unnecessary paperwork.