The Collaborative International Dictionary of English v.0.48:

Facto \Fac"to\, adv. [L., ablative of factum deed, fact.] (Law)
   In fact; by the act or fact.
   [1913 Webster]

   De facto. (Law) See De facto.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

FACTO. In fact, in contradistinction to the lawfulness of the thing; it is
applied to anything actually done. Vide Ex Post Facto.