Sui generis
A similar case that led to the use of the label "sui generis" is the relationship of New Caledonia relative to France, because the legal status of New Caledonia can aptly be said to lie somewhere between a French overseas collectivity and a sovereign nation. Although other examples of such status for other dependent or disputed territories may exist, this arrangement is unique within the French realm.
History of Sussex
Borough-English was the custom that lands should descend to the youngest son or daughter, or, in default of issue, to the youngest brother of the deceased. The name originated from a case in Nottingham in 1327 when the English borough, or part of the town, held to ultimogeniture, the French (Norman) part to primogeniture. In Sussex, inheritance by Borough-English, could still be found on 134 manors after 1750.