Earlier quoted context omitted.
It wouldn't have any value for lack of actual provenance (you can test this by trying to sell your own copy of Fidenza, please report back).
What part of the NFT protocol verifies provenance? And why did this not work for Davidson Carvalho, who hasn't seen a cent of the money made by someone selling NFTs of his work? If there was no provenance, why did anyone pay $170,000 for them? [1] Could it be the case that the NFT market doesn't give two figs about provenance? [1] https://twitter.com/colorblindmess/status/145059819884259328...
e.g. if your Art Blocks NFT is on the Art Blocks contract, it's authentic. If it's the same image on a different contract, it's inauthentic.
Just saw your edit: now that it's known that the art is stolen from a different artist, I would expect the original NFTs to lose most if not all of their value. The convention of authenticity is a social one. If an artist misrepresents art as their own then it seems authentically theirs until shown otherwise. Same as e.g. selling prints of someone else's work.