law: 13. Restrictions respecting right to form association, freedom of speech, etc.
  (1) No person subject to this Act shall, without the previous sanction in writing of the Central Government or of the prescribed authority,
  (a) be a member of, or be associated in any way with, any trade union, labour union, political association or with any class of trade unions, labour unions or political associations; or
  (b) be a member of, or be associated in any way with, any society, institution, association or organisation that is not recognised as part of the Force or is not of a purely social, recreational or religious nature; or
  (c) communicate with the press or publish or cause to be published any book, letter or other document except where such communication or publication is in the bona fide discharge of his duties or is of a purely literary artistic or scientific character or is of a prescribed nature.
  Explanation.
  If any question arises as to whether any society, institution, association or organisation is of a purely social, recreational or religious nature under clause (b) of this sub-section, the decision of the Central Government thereon shall be final.
  (2) No person subject to this Act shall participate in, or address, any meeting or take part in any demonstration organised by any body of persons for any political purposes or for such other purposes as may be prescribed.