I'd also add in the CITES argument to this mix (
link to CITES thread).
This is an added layer of complexity. Many weapons have ivory, tiger parts, turtle shell, rhino horn and other material from endangered species. Unless you have a provenanced item that pre-dates the CITES ban on that species, you can't move that item out of its homeland. Antiques are exempt from the ban (within the limits of the link above, and they aren't small).
So there is an irony here. When something becomes valuable as an antique, it may also be more able to travel beyond its homeland.
Personally, I'd say that if you're worried about this, you better be worrying about properly curating your collection with the best available techniques. That way, your collections will live on after you pass, and if the descendants of the original owners want them back, they will still be around to go back.
Best,
F