The Collaborative International Dictionary of English v.0.48:

disqualify \dis*qual"i*fy\ (d[i^]s*kw[o^]l"[i^]*f[imac]), v. t.
   [imp. & p. p. Disqualified (d[i^]s*kw[o^]l"[i^]*f[imac]d);
   p. pr. & vb. n. Disqualifying.]
   1. To deprive of the qualities or properties necessary for
      any purpose; to render unfit; to incapacitate; -- with for
      or from before the purpose, state, or act.
      [1913 Webster]

            My common illness disqualifies me for all
            conversation; I mean my deafness.     --Swift.
      [1913 Webster]

            Me are not disqualified by their engagements in
            trade from being received in high society.
                                                  --Southey.
      [1913 Webster]

   2. To deprive of some power, right, or privilege, by positive
      restriction; to disable; to debar legally; as, a
      conviction of perjury disqualifies a man to be a witness.
      [1913 Webster]

WordNet (r) 3.0 (2006):

disqualifying
    adj 1: depriving of legal right; rendering legally disqualified;
           "certain disabling restrictions disqualified him for
           citizenship" [syn: disabling, disqualifying] [ant:
           enabling]