ignorance of copyright law won't save you here. i can't legally torrent a copywrited music file just because "no tos to agree to" when i listen to it.
> If you download some copyright material somehow and don't share it with anyone, there is no caselaw that says anything about it.
this is still a violation of the law. you cannot download copyrighted material against the terms of the copyright holder (like downloading a movie or album).