Source : Webster's Revised Unabridged Dictionary (1913)

Canonist \Can"on*ist\, n. [Cf. F. canoniste.]
   A professor of canon law; one skilled in the knowledge and
   practice of ecclesiastical law. --South.

Source : WordNet®

canonist
     adj : pertaining to or characteristic of a body of rules and
           principles accepted as axiomatic; e.g. "canonist
           communism"
     n : a specialist in canon law