El Fuero Juzgo, the Jurisdiction, is a set of laws that were used to govern a region, whose origin dates back to the Middle Ages, during the time of the Visigoth kings, a series of kings those came from the Germanic zones.
"After the agreement of Tudmir, in 713, by which the Visigothic king Teodomiro yields to the Muslim conquerors the territories of the Valley of the Segura, Abderraman II in 825 founds the city of Murcia like administrative capital of the former Cora of Tudmir. The Muslims would govern the city during the next four centuries until by a new pact, agreement of Alcaraz, in 1243, the Muslim kingdom of Murcia was incorporated to Kingdom of Castile. The year 1266 would still have to come to the Castilian government, after Jaime I of Aragon, to quell the Mudejar revolt. The 14 of May of 1266, Alfonso X sends to Murcia the privilege by which it grants the Law of Seville, like legal document founding to create the council and to organize the government of the city and its municipality."
"The great interest of this book for the study of history, law, philology, the birth and evolution of the Castilian language (Spanish language), the paleography ... can be verified in the abundant and excellent studies carried out by researchers, especially of the University of Murcia, whose review is easy to find for those interested."
"This codex, compendium of Visigothic laws, will be the basis for organizing, governing and administering this Council and its vast territory, and today it is preserved virtually intact, except for the covers and some pages, in the Municipal Archive of Murcia."
You can find any general information about Fuero Juzgo at wikipedia.