Decretist

from The Collaborative International Dictionary of English v.0.48

Decretist \De*cre"tist\, n. [LL. decretista, fr. decretum: cf.
   F. d['e]cr['e]tiste. See {Decree}, n.]
   One who studies, or professes the knowledge of, the
   decretals.
   [1913 Webster]