Without a provenance, an object has no history. It is merely an object of undetermined date from an undetermined geographic region.
This past summer, I was at the ruins of the ancient Mayan city of Calakmul just north of the Guatemalan border.
One hundreds years ago, the site had stelae that were masterpieces of ancient Mayan art.
Today, many of those stelae have nothing on their front except saw-marks made by looters in order to sell the sculpture fragments to private art collectors.
For an American perspective, imagine Frenchmen coming in the dead of night with chainsaws to cart off and sell pieces of Mount Vernon to Japanese historical artifact collectors.
So then why is Italy all up in arms about Getty? After all, if they dug it up, or purchased it from someone who did, why would Italy care. After all Italy was not planning to dig for it. Nor does it have a provenance, therefore it must be valueless.
This so called "provenance" seems like a code word for "our blessing".