John of Ibelin

Also known as the Old Lord of Beirut, Jean d'Ibelin le Vieux

Lord of Beirut, regent of the kingdom, and author of the Livre des Assises — the defining figure of 13th-century baronial politics and the principal architect of the Ibelin party that opposed Frederick II.

John of Ibelin was the eldest son of Balian of Ibelin (the defender of Jerusalem in 1187) and the dowager queen Maria Komnene. He was bailli of the kingdom for the young queen Maria of Montferrat (1205–10), lord of Beirut from 1197, and the leading figure of the great Ibelin family throughout his long life.

His central historical role came in the long War of the Lombards (1228–43), the constitutional crisis between Emperor Frederick II — who claimed the kingdom in right of his wife Yolande — and the local barons led by John, who insisted that imperial power was constrained by the kingdom's customary law and the consent of the Haute Cour. John defeated Frederick's imperial bailli Filangieri in the field, drove him from Cyprus, and consolidated the practical independence of the local nobility from imperial direction.

His Livre des Assises, completed shortly before his death, is the longest and most ambitious surviving treatise of the Assises de Jérusalem. Written from the standpoint of a 13th-century baronial constitutionalist, it is at once an attempt to record the kingdom's customary law and a statement of the political theory by which that law constrained kingship — and it has shaped every subsequent reading of the kingdom's political life.

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