while there is nothing that prevents you from making copies. there can be a certificate of original purchase issued to you and registered/signed to a specific u

while there is nothing that prevents you from making copies. there can be a certificate of original purchase issued to you and registered/signed to a specific user's public key in a cloud database. upon sale of the electronic item, you can re-sign/update the cloud cert with the new owner's key. so if a it came to proving that you own the music, you can reference a cloud database and decrypt the signature. it's really the only way forward that comes to mind without being invasive but still allowing enforcement.