What is the statute of limitations on internet piracy?

The owner of a copyright may file an infringement lawsuit up to three years after he learns, or as a reasonably diligent person should have learned, of the allegedly infringing conduct. Downloading “copy written materials from internet sources,” however, is very, very often not an infringement of the copyright in that material. A great many sources of published material include a “Print” function adjacent to the material in order to facilitate copying – which, as a legal matter, is the grant of a license to copy that material for personal use. Moreover, even absent that “print” function, making one digital copy of a work protected by copyright which is then stored solely for personal use in a home computer is also not an infringement of the copyright [under the de minimis copying doctrine]. In addition, the law expressly includes a “fair use” right to use others’ copyright-protected material without license when, essentially, the public benefit of that use outweighs the government-conferred, private right to manage how others use that material. Speak with your own copyright attorney if you have a real-world, present day issue to be resolved.

Your "friend" will probably soon receive notice from the ISP regarding the download with directions to the entity demanding payment. The statute of limitations within which the "entity" will have to act will likely vary from State to State but will probably be either 2 or 3 years from the date the "entity" discovers the download. See an intellectual property attorney or your friend can wait for the letter from the ISP and then contact counsel.

Three years from "accrual" [when known or should have been known by copyright owner] http://www.law.cornell.edu/uscode/text/17/507 Fair use or authorized downloading is not illegal, but I take it you are wondering as to illegal downloading. The vast majority of illegal downloads are never caught, but those caught are notified relatively promptly, usually within about three months.