This volume, the third in the series dedicated to the figure of Iulius Paulus who was an authoritative exponent of Severian legal science. It reconstructs the content of a work that we would be wrong to consider minor, comparing it with the Libri ad Edictum: the commentary on the Lex Iulia et Papia, a normative measure of the Augustan age. The examination of his texts, transmitted to us by the Justinian compilation, allows us to take a look at the methods and techniques of the jurist that, elsewhere, Pauline writing rarely proposes. His commentary on the Lex Iulia et Papia gives readers an unusual point of view on the relationship between jurisprudential tradition and the lex. The commentary on a normative measure - which only a hasty glance could lead us to believe to be an activity subordinate to political power - enables us to perceive the extent to which Paul, at the height of the 3rd century AD, assessed the weight of his own scientific authority towards the other exponents of his discipline and, at the same time, the princes themselves.