[nlarew]

What would Taylor Swift do right now? I can rip all of her audio off of Spotify and use it in my movie without her permission even though she owns the music.

She would try to stop me - maybe send a cease and desist, sue, or otherwise seek remuneration for unauthorized use of her work.

Her proof of ownership is a signed contract with her recording company and any US copyright filings.

Your proof of ownership is an unambiguous cryptographic scheme (NFT), which you could use to secure a US copyright.