The Collaborative International Dictionary of English v.0.48:

Arrogate \Ar"ro*gate\, v. t. [imp. & p. p. Arrogated; p. pr. &
   vb. n. Arrogating.] [L. arrogatus, p. p. of adrogare,
   arrogare, to ask, appropriate to one's self; ad + rogare to
   ask. See Rogation.]
   To assume, or claim as one's own, unduly, proudly, or
   presumptuously; to make undue claims to, from vanity or
   baseless pretensions to right or merit; as, the pope
   arrogated dominion over kings.
   [1913 Webster]

         He arrogated to himself the right of deciding
         dogmatically what was orthodox doctrine. --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

arrogate
    v 1: demand as being one's due or property; assert one's right
         or title to; "He claimed his suitcases at the airline
         counter"; "Mr. Smith claims special tax exemptions because
         he is a foreign resident" [syn: claim, lay claim,
         arrogate] [ant: forego, forfeit, forgo, give up,
         throw overboard, waive]
    2: make undue claims to having [syn: arrogate, assign]
    3: seize and take control without authority and possibly with
       force; take as one's right or possession; "He assumed to
       himself the right to fill all positions in the town"; "he
       usurped my rights"; "She seized control of the throne after
       her husband died" [syn: assume, usurp, seize, take
       over, arrogate]