the only sources I would know of would be court cases where people have been fined or whatever. I can't think of any off the top of my head (in Canada the police have said they have better things to do than enforce corporate copyrights).
There are ways he probably could download it legally. If he downloaded it from a site where he payed for it, it's legal provided the site has the consent of the copyright owner.
I think your friend is confusing "legal" with "not enforced"