Henry III was King of England in succession to King John and is credited with establishing the Jersey legal system which still exists to this day, although he may, in fact, just have formalised the situation which was already in existence when the islands were retained by John after he lost control of the rest of Normandy
In 1221 Henry III wrote to the new Warden of the Isles Philippe d'Aubigné the younger "Rule the Islands by right and due custom, as they have been accustomed to be ruled at the time of our ancestors, Kings of England"
In 1248 Henry III called upon the people of the Islands to declare what these customs were which they claimed to be governed by. They declared that King John instituted twelve Coroners, sworn to hear law cases and rights pertaining to the Crown; and that for the security of the Island the Bailiff hold law cases without the King’s writ. This system of the 12 Jurats appears to have been in existence before the reign of King John; he merely formalised it. It was important for the Bailiff and Jurats to be able to try cases without the King’s permission because it was becoming increasingly difficult for the King to send Justices to the Island. This was because his English Justices knew nothing of the language or the laws of the Island. So in effect Henry III was creating a complimentary, parallel system to that of England to replace an earlier system lost with the Duchy.