law: The Prevention of Terrorism Act, 2002
  51. Officers
  
  competent to investigate offences under this Act.-
  Notwithstanding
  
  anything contained in the Code, no police officer,-
  a.  
  
    in
  
  the case of the Delhi Special Police Establishment, below the rank of a Deputy
  
  Superintendent of Police or a police officer of equivalent rank;
  b.  
  
    in
  
  the metropolitan areas of Mumbai, Kolkata, Chennai and Ahmadabad and any other
  
  metropolitan area notified as such under sub-section (1) of section 8 of the
  
  Code, below the rank of an Assistant Commissioner of Police;
  c.  
  
    in
  
  any other case not relatable to clause (a) or clause (b), below the rank of a
  
  Deputy Superintendent of Police or a police officer of an equivalent rank,
  
  shall investigate any offence punishable under this Act.