The Collaborative International Dictionary of English v.0.48:

Discretional \Dis*cre"tion*al\, Discretionary
\Dis*cre"tion*a*ry\, [Cf. F. discr['e]tionnaire.]
   Left to discretion; unrestrained except by discretion or
   judgment; as, an ambassador with discretionary powers.
   Discretionally

WordNet (r) 3.0 (2006):

discretional
    adj 1: having or using the ability to act or decide according to
           your own discretion or judgment; "The commission has
           discretionary power to award extra funds" [syn:
           discretionary, discretional]