The Collaborative International Dictionary of English v.0.48:

Arrogation \Ar`ro*ga"tion\, n. [L. arrogatio, fr. arrogare. Cf.
   Adrogation.]
   1. The act of arrogating, or making exorbitant claims; the
      act of taking more than one is justly entitled to. --Hall.
      [1913 Webster]

   2. (Civ. Law) Adoption of a person of full age.
      [1913 Webster]

WordNet (r) 3.0 (2006):

arrogation
    n 1: seizure by the government [syn: confiscation,
         arrogation]