The Collaborative International Dictionary of English v.0.48:

Warrantable \War"rant*a*ble\, a.
   Authorized by commission, precept, or right; justifiable;
   defensible; as, the seizure of a thief is always warrantable
   by law and justice; falsehood is never warrantable.
   [1913 Webster]

         His meals are coarse and short, his employment
         warrantable, his sleep certain and refreshing. --South.
   [1913 Webster] -- War"rant*a*ble*ness, n. --
   War"rant*bly, adv.
   [1913 Webster]