Everyone who follows the IP business knows about RIAA v. Verizon -- the D.C. Circuit ruling that section 512(h) of the DMCA does not empower a copyright holder to lay a subpoena on an ISP demanding the identity of an unauthorized P2P music downloader, unless it has already filed formal legal action against an unknown "John Doe."
It turns out that the issue is not closed. RIAA subpoenas are also being litigated in the 4th and 8th Circuits, and in those venues the industry is arguing that the D.C. Circuit was wrong. The cases are still at the trial level, or at preliminary stages of appeal, so briefs are not yet available, but the crux of the RIAA's argument can be found in the opinion of the district court that was reversed by the D.C. Circuit. Also, the industry has not yet decided whether it will seek rehearing en banc or Supreme Court review of RIAA v. Verizon.
An analysis of the issues, written before the D.C. Circuit decision, is here. Many experts were surprised by the D.C. Circuit decision, so the other circuits could come to a different conclusion.