I always laugh at archaeologists who get all upset at people who keep found arrowheads and such. I tell them that if I find out who owned those things, of course I’ll return them. Until then, finders keepers, and if you want to study artifacts, get out there and find them yourself.
I don’t, however, approve of dealer types who will mine an entire site just to sell the stuff. If that’s inconsistent, too bad.
Frankly I despise the “you MUST hand over any little scrap of artifact from a battle site”, or anything found on “federal” land including paleontological fossils.