Arkansas Board of Corrections could not overturn the existing policy of accepting books from approved distributors, because it had been enacted by the Arkansas state legislature. Therefore, the state legislature had to approve any changes. No date has been set for the legislature to consider the ban, which would require 30 days for public comment before a vote. Meanwhile, the current policy, that "Inmates may receive publications from recognized commercial, religious, or charitable outlets", remains in place.
tl;dr - Old policy still in place until they decide how best to fuck everyone.