machine guns are legal to own in VA, if i am not mistaken. if he doesn't have it on the premises in DC and has it in one of the multiple manses owned by wifey elsewhere, he is probably ok. i have no idea about bringing stuff home from the service.
I believe the first Gulf War was the first time our military members were not allowed to bring home firearms that would be legal in the U.S. as souvenirs.
I thought full automatic weapons were outlawed (by Congress) in the 1930s, in one of the initial impositions of gun control, to control the gang violence of the time. Think Valentines Day Massacre.
The media relies on people not knowing the difference between full auto and semi-auto when they demagogue the RKBA issue.
It should be noted that there are kits to convert semi-auto versions into full-auto, and if the media would report the whole story clearly I would accept this as a valid counterargument.