decretal
noun
de·cre·tal di-ˈkrē-tᵊl 
ˈde-kri-tᵊl
: decree
especially : a papal letter giving an authoritative decision on a point of canon law
Word History
Etymology
Middle English, from Anglo-French, from Late Latin decretalis of a decree, from Latin decretum decree
First Known Use
14th century, in the meaning defined above