Nothing in this Chapter affects the power of the DPP—
(a) to file an indictment against a person for an offence if, on a committal proceeding conducted in relation to a charge for that offence, the Magistrates' Court ordered the person to be discharged on the charge; or
(b) to discontinue a prosecution under section 177, or not to take within the period prescribed by section 163 any step mentioned in that section, in relation to a charge on which a person was committed for trial.