The decision to reprint this study, which has always been almost impossible to find, is not only mine but also that of the author himself, who had prepared an edition in 2007, with the active collaboration of Saverio Di Bella. It was from him that I received the corrected copy of the work, so my only task is to respect the wishes of the Maestro and to make use of his handwritten notes in the margins, editing this second edition and ensuring that it is published on the first anniversary of his death. I hope that this will keep the bond with the Maestro alive and honour his memory.

This monograph continues only in part – in the last chapters – that on the Apostolic Legation1 with which, at only twenty-four years of age, Catalano had made a brilliant debut on the scientific scene, demonstrating his historical interests that anticipated his legal ones (religious freedom, the issue of concordats, Article 7 of the Constitution, etc.) which came shortly afterwards. These are studies to which Catalano remained attached throughout his life (the Legazia was reprinted in 1973, together with an article on its origins – 1088-1178 –2) and which he continued to cultivate.