The Codex Gregorianus, or Gregorian Code, was compiled by an otherwise unknown man named Gregorius at the end of the third century A.D. It started a centuries-long tradition of collecting Roman emperors' laws in a single manuscript.
The Codex Gregorianus covered the laws of Hadrian, who ruled from A.D. 117 to 138, to those of Diocletian, ruler from A.D. 284 to 305.
Later codices excerpted the laws that were still relevant and added new ones, so only parts of the first codex survived as passages in other editions. All copies of the original collection of laws were thought to have been lost.
Luckily, in the 16th century it was common to use scraps of parchment to reinforce the bindings of new books.
Seventeen such fragments—each smaller than 2 square inches (13 square centimeters)—were recovered from a set of books decades ago. The scraps were eventually acquired by a private owner, who recently loaned them to Roman-law experts at University College London.
A preservation librarian who examined the scraps told the researchers that the shapes of the pieces and the patterns of wear suggest the ancient parchment had been wrapped around cords that went over the books' spines.
"We saw a couple key phrases and realized this was a kind of legal text," said study leader Benet Salway. "We matched it against the database of legal pronouncements we had, and found it didn't match anything."
But a few of the phrases matched passages in the Justinian Code, compiled in the sixth century, leading the team to conclude that the unfamiliar sections were from a source text: the Codex Gregorianus.
The fragments themselves are not from the original codex, but they could be from a copy that dates back as far as A.D. 400, the researchers said.
Only the fragments containing text that overlaps with known parts of the Justinian Code could be translated, and that text deals with appeals and the statute of limitations for an unknown matter.
But the fragments were annotated between the lines in Greek, a commonly spoken language by the end of the fifth century, implying that this particular copy of the Codex Gregorianus was used heavily, Salway said.
"The language of the law was Latin, but a lot of users of this text [would have been] Greek speakers, and they'd need to be able to understand it."
Since the pieces were found inside an unrelated book, the find doesn't increase the researchers' chances of locating the rest of the Codex Gregorianus. But "what I would hope is that it raises awareness of the possibility of this still being out there," Salway said.
"I'm not advocating that all [16th-century] books' bindings be ripped off—though we might find all sorts of interesting things in there—but when these books are conserved, care should be taken to see what is inside."