I am reading an interesting book called Unintended Consequences by John Ross.
It's an interesting read so far as it looks at our gun laws up through the 20th century...I am at the NFA of '68 now.
Basically up to the NFA of '34 any citizen could own any kind of weapon.
The theory is, after prohibition the government had all of those Treasury agents sitting around and rather then lay them off the NFA of '34 was passed. To own a machine gun, sawed off shotgun, etc. you had to pay $200- and get a stamp per weapon. This new law was enforced by the Treasury Department.
The government passed it using the excuse that it would stop gangsters from using certain weapons. It is believed that in actuality it was passed to keep the "G" men employed post prohibition. Now you know as well as I do, old Al Capone would have had no problem paying $200- for the right to own a Tommy gun but the average citizen couldn't afford that. Mmmmmm?
Many judges post the NFA '34 felt the law was unconstitutional and when a person was brought before the judge on gun charges, (Owning a machine gun without the prepaid $200 stamp as an example) and if the gun was standard issue in the military, they would throw the case out.
Some of these lower court decisions were challenged by the Treasury Department but many were not. The judges used the logic that the Second Amendment to the Constitution states that: A well regulated militia being necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed. . So if the military used a weapon and a citizen could afford it, they could own it.
In the book, I am now at the NFA of '68. I will fill you in once I read those chapters; However, I suspect that the '68 law was an emotional one based on JFK's assassination. More to come...