10. Matters not subject to investigation.

(a) any matter in respect of which a formal and public inquiry has been ordered with the prior concurrence of the Commission;
(b) any matter which has been referred for inquiry, under the Commissions of Inquiry Act, 1952 (Central Act 60 of 1952) [* * *] ;
(c) any complaint made after the expiry of five years from the date on which the matter complained against is alleged to have taken place: