The Law of Citations and Classical Texts in the Post-Classical Period

One implication of the Valentinian Law of Citations which is important for the history of juristic texts in the post-classical period seems to have been ignored. This constitution made the works of the five jurists, Papinian, Paul, Gaius, Ulpian and Modestinus, primary authorities. The works of jurists cited by the five could also be produced, provided in this case that, because of the age of the works, what these jurists said was confirmed by collation of manuscripts. In the case of the five primary authorities no collation of manuscripts was demanded. Why was there this difference? There are, I submit, two possible explanations