What is The Decrees And The Decretals?

Legal Definition
The decrees are ecclesiastical constitutions made by the popes and cardinals. The decretals are canonical epistles written by the pope, or by the pope and cardinals, at the suit of one or more persons, for the ordering and determining of some matter of controversy, and have the authority of a law. As the decrees set out the origin of the canon law, and the rights, dignities, and decrees of ecclesiastical persons, with their manner of election, ordination, etc., so the decretals contain the law to be used in the ecclesiastical courts. Jacob.
-- Black's Law Dictionary