The Collaborative International Dictionary of English v.0.48:

Fecial \Fe"cial\, a. [L. fetialis belonging to the fetiales, the
   Roman priests who sanctioned treaties and demanded
   satisfaction from the enemy before a formal declaration of
   war.]
   Pertaining to heralds, declarations of war, and treaties of
   peace; as, fecial law. --Kent.
   [1913 Webster]