law: 27. Members not to vote on matter in which they are interested.
  No member shall vote at a meeting of the Council or of any Committee thereof on any question relating to his own conduct or vote or take part in any discussion on any matter (other than a matter affecting generally the residents of New Delhi) which affect his pecuniary interest or any property in respect of which he is directly or indirectly interested, or any property of or for which he is a manager or agent.