They have a copy, you through your action cause it to be duplicated to your machine. You make the copy, they present their copy to be duplicated without license. You both commit tortuous malfeasance unless you can claim an exclusion such as (in the USA) for news reporting or certain educational uses (http://en.wikipedia.org/wiki/Fair_use#Fair_use_under_United_...).
I'm going to make a bit of a ridiculous scenario here, but I'm curious. What happens if a site has a fixed number of copies and then transfers them to the downloaders? Does it being digital matter as opposed to a run of pirate discs?
Do I still have fair use rights for the ephemeral buffers used to play a file even if I got it illegitimately?
>a site has a fixed number of copies and then transfers them to the downloaders //
It's a kind of interesting question in technical terms. However the law gets interpreted practically and judges are very good at seeing through these sorts of "clever" ideas: if the site doesn't have a license to distribute then they're acting unlawfully. If they purchased copies and then transferred them, destroying their own copies then there's nothing in copyright law generally - that I know of - that is a problem. Lending an e-book to a friend is allowed under copyright as much as lending a paper bound book. It is highly likely however that the seller has attempted to add contractual obligations in your use of their e-reader and at your purchase of the e-book ... whether those terms are legal or not is a whole heap of legal spaghetti that I'm not really competent to pronounce on.
Jurisdictions vary on the difference between holding and using a copy but pretty much it's like receiving stolen goods (though of course copyright is not theft, I'm making an analogy); if you know they're stolen then you're guilty, if you don't know then you're still guilty but the courts don't tend to punish you and you are likely only going to have to return the goods (or in copyright terms pay actual damages).
The media in which a work is created is not especially important. So a digital work in general terms should be treated the same as others - however the nature of the media means there is movement and some stretching of the law. For example with e-books you could automate sharing so that you buy in to a pool of books that are shared whenever you wish to read; you get a contention factor (like when using broadband) and effectively you may only have to pay a-hundredth of the cost of the book (plus the service charge) in order to read the book whenever you wish ... this is not illegal AFAICT [I'm not entirely up on US copyright though] but it's probably contrary to the spirit of the law and unlikely to have been in mind particularly when 100+ year old international treaties were first drafted.
>fair use rights [...] illegitimately //
These are contradicting terms.
If you have a fair use right to a copy then you didn't get it illegitimately you got it within the legal bounds of the copyright law. I imagine you're thinking if you use bit-torrent to download a work that you have a fair-use "license" to use. Well of course the people uploading to you probably are infringing, though you'd never know if they have a license or not, and you don't have a license to upload. You might fall foul of provisions against derivative works, for example if the work was edited to remove attributions or copyright notices, but I don't see why you'd be judged to have committed a tort provided you have a genuine fair-use right to duplicate the work and you ensure you're within the lines on the above mentioned issues.
Gah. Got carried away there. Verbosity is a weakness of mine.
