How did feudalism change Germanic law from a personal system to a territorial system?

The transition from a personal to a territorial system in Germanic law was driven by the rise of feudalism following the disintegration of the Frankish kingdom in the 9th century.1

Originally, Germanic law was personal, meaning it applied only to individuals based on their tribal or national identity, regardless of where they lived. However, as central government decentralized, powerful lords gained independence and established control over specific regions. These lords held courts for all their vassals and tenants, applying the same local custom to everyone within their jurisdiction, irrespective of their racial or national origin.21

This shift replaced the old personal principle with the territorial principle, where the law was defined by the custom of the region. This feudal law was often a blend of Germanic traditions and Roman law, adapted to serve the interests of the feudal lords. Consequently, the legal focus moved away from the tribal affiliations of the individual toward the authority exercised by a lord over a defined territory and its inhabitants.1