Contrary to popular belief, downloading any sort of copyrighted material is illegal regardless of current ownership, it's almost the same as the delete after 24 hours myth. If you own the actual media in question, then you can make a backup like everyone else. There is zero reason to download something you already own and it's quite a contradiction when you can easily make a legal backup.
Furthermore, there is no way to actually prove you own the original media and pictures can easily be faked on the internet.
Furthermore, there is no way to actually prove you own the original media and pictures can easily be faked on the internet.