Notwithstanding anything contained in the Code of Criminal Procedure, 1973 (2 of 1974), no police officer below the rank,--
         (a) in the case of the Delhi Special Police Establishment, of an Inspector of Police;
         (b) in the metropolitan areas of Bombay, Calcutta, Madras and Ahmedabad and in any other metropolitan area notified as such under sub-section (1) of section 8 of the Code of Criminal Procedure, 1973 (2 of 1974), of an Assistant Commissioner of Police;
         (c) elsewhere, of a Deputy Superintendent of Police or a police officer of equivalent rank,
shall investigate any offence punishable under this Act without the order of a Metropolitan Magistrate or a Magistrate of the first class, as the case may be, or make any arrest therefor without a warrant:
     Provided that if a police officer not below the rank of an Inspector of Police is authorised by the State Government in this behalf by general or special order, he may also investigate any such offence without the order of a Metropolitan Magistrate or a Magistrate of the first class, as the case may be, or make arrest therefor without a warrant:
     Provided further that an offence referred to in ¹[clause (b) of sub-section (1)] of section 13 shall not be investigated without the order of a police officer not below the rank of a Superintendent of Police.