Sounds like the nuthead 2.5 miles down the road (next village) from me who has a Churchill tank parked in his yard. AFAIK nobody is bothering him. He is not paying road tax on it and as far as I know it does not have a valid MOT and insurance :)
Nobody bothers other nutheads either. I nearly crashed into a wall of an old house in the Czech republic last year. I was driving peacefully down the road and from behind the bend came out a WW2 Willis with a twin Erlicon 50 cal mounted in the boot barrels pointing straight at me (the incoming traffic). I nearly lost control there and then.
My granddad used to own a WW2 BMW bicycle with a sidecar (it was supposed to be mine when I grow up, but my older cousin destroyed it by smashing in it). In full SS regalia with markings, nazi crosses, etc (AFAIK it was abandoned after a mechanical problem by the guys assigned to arrest him and execute him on the spot in 1944 - two weeks before the country was liberated). The only thing the milicia (on the other side of the iron curtain) made him do was to remove the machine gun and hand it in.
And so on. They should just leave the history buff alone. He is harmless.