Section 211(5)(a) in The Tamil Nadu Building and other Construction Workers (Regulation of Employment and Conditions of Service) Rules, 2006
(a)the Government are of the opinion that the matter of the enquiry or any part of it are of such nature that it would be against the interests of national security to hold the enquiry in public and directs the said authority or the enquiry officer, as the case may be, to hold the enquiry in camera; or