The discovery of fragments of the lost Codex Gregorianus, one of the oldest known law books, was announced today. I'm guessing it will receive a lot of press coverage, but for the full story I recommend going to the UCL web site, and hearing the report of those that discovered it: Fragmenta Londiniensia Anteiustiniana by Simon Corcoran and Benet Salway
The codex was compiled by a private individual named Gregorianus, but soon became a reference book for Roman law. It dates from the 3rd century or reign of Constantine. More info at Lacus Curtius.