What is Decretales Gregorii Noni?

Legal Definition
The decretals of Gregory the Ninth. A collection of the laws of the church, published by order of Gregory IX. in 1227. It is composed of five books, subdivided into titles, and each title is divided into chapters. They are cited by using an X, (or extra;) thus "Cap. 8 X de Regulis Juris," etc.
-- Black's Law Dictionary
Legal Definition
A collection of ecclesiastical laws published under Gregory IX in 1227.
-- Ballentine's Law Dictionary