This first official code was the basis of the second part of the Corpus juris canonici.
It includes the constitutions subsequent to were included in the edition of Jean Chappuis in 150o; they passed into the later editions, and are considered as forming part of the Corpus juris canonici.
Much of it, no doubt, was borrowed from the Corpus juris canonici and the English provincial canons.
Perhaps his edition of the Leges Visigothorum (1579) was his most valuable contribution to historical science; in the same line he edited the Capitula of Charlemagne, Louis the Pious, and Charles the Bald in 1588, and he also assisted his brother Francois in preparing an edition of the Corpus juris canonici (1687).
Gregory did good service, moreover, by his reform of the calendar which bears his name, by his emended edition of the Corpus juris canonici and by the creation of nunciatures.
