Although the serfdom of state-owned workers had been abolished long before, the abolition itself was not a momentous revolutionary action.
The state-owned serfs were gradually introduced into their new status, partially by a system of graduate payments to the government and partially by a system of state-employment commissions.
Since the status of state-owned serfs was not abolished at once, their emancipation was happening step by step (and not at equal pace everywhere along the Russian Empire).
Hence, the term refers to the same thing as before: state-owned serfs.
UPD: It has just come up to my mind that the term could refer to a former status of the serfs - that is, 'a serf who originates from the state-owned class'; 'a descendent from the class', provided that there was no new name for the emancipated serfs. The meaning of the Genitive case in this phrase could be similar to that oif Exessive in Votian, Finnish and Estonian. The ultimate solution should be based upon the context of the Imperial Decree, iI guess.