I'm not a layer but I play one on TV. Aren't torrent sites (ie PirateBay) arguing that what they are doing is NOT illegal because they only host the torrent file that has the tracker location with the peers and do not host the actual copyrighted content?
Technically you'd have to go get a court order against the torrent site to release IP information on the seeders/trackers of the content and then go DMCA the ISP and upstream of the person (thousands/millions of them) who are hosting your file for sharing.
http://en.wikipedia.org/wiki/BitTorrent