The Collaborative International Dictionary of English v.0.48:

Extrajudicial \Ex`tra*ju*di"cial\, a.
   Out of or beyond the power authority of a court or judge;
   beyond jurisdiction; not valid as a part of a judicial
   proceeding; as, extrajudicial oaths, judgments, etc., are
   null and void. -- Ex`tra*ju*di"cial*ly, adv.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

extrajudicial
    adj 1: beyond the usual course of legal proceedings; legally
           unwarranted; "an extrajudicial penalty"