The Hexabiblos

The essay's closing move on Byzantine law: six books distilled by a judge in Thessalonica in 1345, still the working civil law of Greece in 1946.

That claim checks out, with qualifications the essay does not have room for. The Hexabiblos was directed to be applied by Greek courts from 1827 and served as the civil law of the new state from 1835 until the Greek Civil Code took effect on 23 February 1946. It did not govern the whole territory: Crete, Samos, the Ionian Islands and the Dodecanese had separate regimes, and the Dodecanese did not come under the new code until 1948.

Worth noting for the essay's argument that this was a private compilation by a working judge, not an act of state. What survived nine centuries of Byzantine legal history was a book someone wrote to be useful.