George Herbert wrote a pretty good summary of the current state of US
law concerning Weapons of Mass Destruction, but I'd like to clarify a
few of his points.
To buy and sell anti-tank guns, rocket launchers, etc., a person needs
a Federal Firearms License. A Class III FFL allows one to deal in
full auto firearms and a few other controlled devices. A Class II FFL,
I believe, is what George is referring to when he spoke of being registered
as an "Arms Dealer". However, a FFL is not required to own controlled weapons,
only to sell them. There is some licensing and paperwork involved to
buy a controlled device, but you don't have to be a registered dealer. A
friend of mine buys C4 plastic explosives and shaped charges for his
business, a oil well perforation service. He has to fill out a ton of
papers, but he doesn't need an FFL to buy.
Tanks and aircraft designed to carry weapons are not classed as weapons
in themselves. Anyone can buy an M3 Stuart tank or a P-51 Mustang, sans
weapons, no problem. What you have to do to disable the weapon carrying
capability depends on the BATF's whim. I knew a group of WWII reenactors
in Oklahoma City who bought a Wehrmacht surplus Hetzer tank destroyer
from a museum in Switzerland in 1981. To legally import into the
country, they had to have the breech block of the cannon cut in half
to disable it. They had this pretty carefully done in Europe, then shipped
it to all to Oklahoma, where they applied for a manufacture permit to
enable the cannon. Once they had the permit from the BATF, they had
the breech welded back together and they had a fully functional light
tank destroyer to play with. Finding cannon shells to fire was a
problem, though.
What's happening today is that the BATF is making up its own rules as it
goes along. If the BATF doesn't want to allow something, they simply
restrict it, regardless of whether or not they have a legal basis to do
so. For instance, there is an Executive order banning the import of
a list of specific weapons into the US. The BATF has taken it upon itself
to expand that list to include weapons are not restricted by the order.
One dealer I've read of got clearance from the BATF to import a number
of rifles, got them as far as a US Customs warehouse, then found that
the BATF had changed its mind. The rifles are sitting in the warehouse,
they are legal to import, but the BATF says no, we won't let you bring
them in. Sue us.
It's the same thing with the Soviet aircraft. There are no real legal
restrictions on the aircraft or their systems, but the BATF is simply
overreaching its authority in what it can control.