The Collaborative International Dictionary of English v.0.48:

disestablishmentarianism \dis`es*tab`lish*men*ta"ri*an*ism\, n.
   The doctrine or political position that advocates abrogating
   the establishment of a church as the official state
   religion..
   [PJC]

         Prior to the Puritans, very few earlier believers
         contended for any form of disestablishmentarianism.
                                                  --David. W.
                                                  Hall (Savior
                                                  or Servant?
                                                  Putting
                                                  Government in
                                                  Its Place: The
                                                  Covenant
                                                  Foundation,
                                                  1996)