How did customary law encourage the creation of forged written records in medieval Europe?

In the context of diplomatics, the study of documents, customary law encouraged the creation of forged records primarily because of the transition from oral traditions to a system that increasingly demanded written substantiation.

During the early Middle Ages, frequent wars and social disturbances often disrupted property possession and legal titles. While many individuals held rights that were perfectly valid under long-standing, unwritten "customary" law, the evolving legal environment necessitated formal written evidence to protect those claims. Consequently, many forgeries were produced to provide this required written proof for legitimate existing rights, leading to a practice where some falsifications were considered "intentionally honest" by their creators.1

Furthermore, the lack of critical judgment by those responsible for certifying copies often facilitated the validation of forged records. When forged documents were included in new, formally certified instruments—such as transumpts—they gained legal legitimacy, effectively embedding the fraud into the official record. This environment, combined with inadequate knowledge of historical documentary forms, allowed forgeries to proliferate until more rigorous philological and technical methods of detection were developed during the Renaissance.21