The Collaborative International Dictionary of English v.0.48:

Cognizable \Cog"ni*za*ble\ (? or ?), a. [F. connaissable, fr.
   conna[^i]tre to know, L. cognoscere. See Cognition.]
   1. Capable of being known or apprehended; as, cognizable
      causes.
      [1913 Webster]

   2. Fitted to be a subject of judicial investigation; capable
      of being judicially heard and determined.
      [1913 Webster]

            Cognizable both in the ecclesiastical and secular
            courts.                               --Ayliffe.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cognizable
    adj 1: capable of being known [syn: knowable, cognizable,
           cognisable, cognoscible] [ant: unknowable]