The Collaborative International Dictionary of English v.0.48:

Decitizenize \De*cit"i*zen*ize\, v. t.
   To deprive of the rights of citizenship. [R.]
   [1913 Webster]

         We have no law -- as the French have -- to decitizenize
         a citizen.                               --Edw. Bates.
   [1913 Webster]