Guernsey was a part of the Duchy of Normandy from early in the 10th century.
When the Duke of Normandy (William the Conqueror) conquered England in 1066 and became King of England as well as Duke of Normandy, Guernsey became annexed to the English Crown. When Normandy was reclaimed from the English Crown by King Philippe Auguste of France in 1204, Guernsey was not reclaimed, and accordingly Guernsey remained annexed to the English Crown as successor of the Duke of Normandy.
The fact that Normandy was lost to King Philippe Auguste did not mean an end to Norman culture and law in Guernsey. Guernsey “customary” law continued to evolve through practical custom over the course of the years, occasionally being reduced into books documenting these customs (known as “coutumiers”), and commentaries on the coutumiers by various authors, most notably Terrien.
Some areas of Guernsey law still retain their roots in customary law. However, other areas, for example criminal and commercial law, are heavily influenced by English law, with the legislation passed in these areas being very similar to English legislation.
Guernsey has its own Court structure, with the judicial committee of the Privy Council generally being the court of last resort. The Bailiff is Guernsey’s chief judge, and is assisted in exercising judicial functions by his deputy (the Deputy Bailiff), and other Judges, Magistrates, Lieutenant Bailiffs and Jurats. The Jurats are a body of elected lay persons, who primarily sit as arbiters of fact in civil and criminal cases.
Other islands in the Bailiwick have their own separate Court structures and judges.
Only persons sworn as advocates by the Royal Court of Guernsey have rights of audience before the Courts.