How did dispositive documents create legal acts?

In the field of diplomatics, documents are classified based on their legal function. Unlike evidentiary documents, which merely record a legal act that has already been performed orally, a dispositive document is one where the act of issuing the document itself constitutes the legal act.1

By creating and issuing the document, the authority—such as an emperor, king, or pope—brings the legal transaction into existence or effect. This distinction emerged in Roman practice as early as the 3rd century CE. While the use of such documents fluctuated after the early Middle Ages, they regained prominence by the late 11th and early 12th centuries, when sealed charters from high secular or ecclesiastical dignitaries were again recognized as having this dispositive power. In this context, the document serves as the primary instrument for establishing legal rights or permanent obligations.1