Liber Extra
Knowing Raymond's reputation in the juridical sciences, Gregory IX asked him to help in the rearranging and codifying of canon law. Canon laws, which were previously found scattered in many publications, were to be organized into one set of documents. In particular papal decretal letters had been changing the law over the course of the previous 100 years since the publication of the "Decretum" of Gratian. Being pleased with Raymond's efforts, the pope announced the new publication in a Bull directed to the doctors and students of Paris and Bologna in September 1234, commanding that the work of Raymond alone should be considered authoritative, and should alone be used in the schools. His collection of canon law, known as the "Decretals of Gregory IX", became a standard for almost 700 years. Canon law was finally fully codified by 1917.