The Collaborative International Dictionary of English v.0.48:

Unlawful \Un*law"ful\, a.
   Not lawful; contrary to law. -- Un*law"ful*ly, adv. --
   Un*law"ful*ness, n.
   [1913 Webster]

   Unlawful assembly. (Law) See under Assembly.
      [1913 Webster]

WordNet (r) 3.0 (2006):

unlawfulness
    n 1: the quality of failing to conform to law [ant:
         lawfulness]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "unlawfulness":
   aberrance, aberrancy, abnormality, anarchy, anomie, criminalism,
   criminality, delinquency, deviance, deviancy, illegality,
   illegitimacy, illicit business, illicitness, impermissibility,
   improperness, impropriety, inappropriateness, incorrectness,
   indecorousness, indecorum, inequitableness, inequity, infraction,
   iniquitousness, iniquity, injustice, lawlessness, legal flaw,
   outlawry, sinfulness, technical flaw, undueness, unfitness,
   unfittingness, unjustness, unmeetness, unrighteousness,
   unseemliness, unsuitability, violation, wickedness, wrong,
   wrongfulness, wrongness