His nomination was the result of the right of La Rochelle to establish itself as a commune, granted by Guillaume X, Duke of Aquitaine, and upheld by his daughter Eleanor of Aquitaine. Guillaume was assisted in his responsibilities by 24 municipal magistrates, and 75 notables who had jurisdiction over the inhabitants.
This nomination arose from La Rochelle's right to self-governance, granted by Guillaume X, Duke of Aquitaine, and upheld by his daughter Eleanor of Aquitaine. Guillaume shared authority with 24 municipal authorities and 75 influential figures who governed the inhabitants.