law: The Delhi Municipal Corporation Act, 1957
  144. Permission of the Commissioner to become void in certain cases.-
  The permission granted under section 143 shall become void in the following cases, namely:-
  (a) if the advertisement contravenes any bye-law made under this Act;
  (b) if any material change is made in the advertisement or any part thereof without the previous permission of the Commissioner;
  (c) if the advertisement or any part thereof falls otherwise than through accident;
  (d) if any addition or alteration is made to, or in the building, wall, hoarding, frame, post or structure upon or over which the advertisement is erected, exhibited, fixed or retained if such addition or alteration involves the disturbance of the advertisement or any part thereof; and
  (e) if the building, wall, hoarding, frame, post or structure over which the advertisement is erected, exhibited, fixed or retained is demolished or destroyed.