The Collaborative International Dictionary of English v.0.48:

Irenarch \I"re*narch\, n. [L. irenarcha, irenarches, Gr. ?; ?
   peace + ? to rule.] (Gr. Antiq.)
   An officer in the Greek empire having functions corresponding
   to those of a justice of the peace. [Written also
   eirenarch.] Irenic