The way the law is written in the US - and in many other parts of the world - only the uploader has the capacity to infringe. Not everyone realizes it, and rightsholders say that downloaders are also culpable. But, the US law does not specifically declare receiving a copy to be an infringing act.

For a downloader to be infringing, they would have to be culpable for uploading as well as downloading. The downloader would have to conspire with the uploader to commit infringement. Rightsholders have tried to make this argument with public trackers, but they have never succeeded. As far as I know, this argument has never been tried with private trackers. The process and requirements of joining and participating in a private tracker may very well be enough to support a conspiracy charge.