I spent a long time doing reasonably deep dives into the legal nature of tokens, blockchain-based ownership and so on. Nevertheless, I'm not a lawyer, this is not legal advice.<p>Most "digital art" NFTs do not confer any particular rights in relation to the artwork in question. Unless you have a written agreement which states otherwise, you do not have any rights at all, except for rights over the NFT. The NFT does <i>not</i> give you the right to make copies of the artwork, to claim royalties from others who make copies, or to issue DMCA takedowns or similar. This is for the simple reason that the copyright in the artwork is retained by the original artist unless agreed otherwise. This is, of course, true of physical art too: I can buy a physical Banksy, but Banksy keeps the copyright and can decide to deny or permit the making of copies.<p>When I buy the physical artwork, what I'm buying is the fact that the artist personally created it. I could buy a print, but even if it is a perfect reproduction it lacks the direct connection to the artist's physical involvement. Because people value authenticity, my authentic artist-created copy is worth more than a print.<p>NFTs work by creating a connection to the artist, albeit a fairly minimal one: the artist's digital key was used to sign a record on the blockchain, and now I own that record (loosely speaking). It is, I suppose, more like owning an autographed copy of a print. However, since this is the most authentic connection we _can_ achieve with respect to digital art, it is deemed (in some cases) to have significant value.<p>In more concise terms: NFTs are not artworks, they are not copies of artworks, they are signed digital records which refer to an artwork, which are valuable because they are (believed to be) signed by the artist.<p>To the original question, then: what happens when someone copies an NFT on to another blockchain? It's not obvious to me how someone would do this. Of course, anyone can create a "fake" NFT just like anyone can create a fake autograph. But "copying" here is very difficult, because you can't create a duplicate of a transaction that was signed by a particular private key unless you have a copy of the private key yourself. So, either the artist is minting multiple NFTs for the same artwork, or someone has stolen their private key.<p>If the artist is minting multiple NFTs, a question we need to ask is whether they ever committed to _not_ doing this. If they did not, then it's hard to see what reason anyone has to complain. If they did commit to this, then the owner of the NFT may have some claim against them (again, this is not legal advice). If there is a social norm against minting multiple NFTs, then the artist's reputation may suffer and the value of all of their current and future artworks will decline. Since some NFTs give the artist a cut of all future re-sales, they do have some economic incentive to avoid doing this. If someone has stolen the private key then we have a very interesting conundrum!