French School, (14th century), French. Century. 'Decree of Gratian' is a collection of religious Canon Law of the Roman Catholic Church, compiled and written in the 12th century by the Italian monk and jurist known as 'Gratian'; the compilation remained in use by the Roman Catholic church until 1917. Materials: vellum. Provenance: Bibliotheque Municipale, Amiens, France / The Bridgeman Art Library.