The Bailiwick of Guernsey is one of three Crown Dependencies.
Separated from the Dukedom and Duchy of Normandy by and under the terms of the Treaty of Le Goulet in 1204, the Bailiwick comprises a number of islands in the English Channel which fall into three separate sub-jurisdictions: Guernsey, Alderney and Sark. Herm is administered as a part of Guernsey.
A bailiwick is a territory administered by a bailiff. The bailiff of Guernsey is the civil head and presiding officer of the States of Guernsey, but not of Alderney or Sark. He is the head of the judiciary of the Bailiwick.