The Collaborative International Dictionary of English v.0.48:

federated \fed"er*at*ed\, adj.
   United by compact under a central organization, as
   governments or commercial organizations.

   Syn: federate.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

federated
    adj 1: united under a central government [syn: federate,
           federated]