The Collaborative International Dictionary of English v.0.48:

nonindulgent \nonindulgent\ adj.
   1. not indulgent. [Narrower terms: austere, forbidding,
      stern ; {blue(prenominal), puritan, puritanical ;
      {corrective, disciplinary, disciplinal ; {monkish ;
      {renunciant, renunciative, self-abnegating, self-denying
      ; {self-disciplined ; {spartan, strict ] Also See
      {abstemious. Antonym: indulgent.
      [WordNet 1.5]

   2. unpermissive. Opposite of permissive.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

nonindulgent
    adj 1: characterized by strictness, severity, or restraint [syn:
           nonindulgent, strict] [ant: indulgent]