My hometown Legion had a couple of Span-Am War vintage .30 Army Colt "Potato Digger" MGs on tripods, and a WWI Lewis Gun, all demilled, in the Legion hall where we had our Boy Scout meetings. Then, all of a sudden, sometime in the late '70s, the BATF out of Des Moines came swooping down and conducted a raid like they thought it was a bunker full of neo-Nazis with M-16s. Everybody thought it was ridiculous -- raiding a locked but empty building.
It took several years and intervention by our local Congressman to get them returned -- they were perfectly legal. Might actually have been a good thing, though, because the Legion hall burned down a couple of years later, while they were in ATF custody. They're now housed in the local Historical Society Museum.