One clear indication of the increasing use of the written word in western Europe from the twelfth century onwards was the compilation of an unprecedentedly diverse and numerous body of legal texts. In part, the growing textualization of law built on earlier foundations. This was particularly true of Roman law, whose rediscovery in Italy in the late eleventh century led to a revival in the study of law. At the same time, the expansion of papal power from the second half of the eleventh century accelerated the production of new collections of canon law, whose compilers sought to impose order upon a mass of written law going back to the earliest councils of the church and also to integrate contemporary additions to that law resulting from conciliar and papal legislation.
Yet the diversification of legal writing also owed much to the compilation of texts of secular customary law, in both Latin and the vernacular. In some societies, such as Iceland and Scandinavia, these texts marked the beginning of written law; in others, including England, France, Germany, and, above all, Italy, where law and legislation had been written earlier in the Middle Ages, the custom of particular kingdoms or provinces was committed to writing in new forms with the compilation of coutumiers. Although their relationship to earlier Welsh legal writing is unclear, the lawbooks of medieval Wales provide a further instance of this textualization of secular custom.
The proliferation of compilations of customary law from the twelfth century onwards raises important issues about both law and literacy in medieval western Europe. In general terms, many of these compilations can be interpreted as reflecting an increasingly widespread conviction, stemming from acquaintance with the authoritative books of Roman and canon law, that law should be in written form. It has also been argued that the influence of the learned laws led to a greater emphasis in customary law on the use of written evidence and the keeping of court records, thereby helping to create a more literate and rational legal culture than that of the early Middle Ages.
Huw Pryce, “Lawbooks and Literacy in Medieval Wales” (2000)