Section 5 in The Chennai Metro Railway (Carriage and Ticket) Rules, 2014
5.
Notwithstanding anything contained in these rules, the members of the Armed Forces of the Union Government, the State Police, the Para-military forces, the National Cadet Corps, and other uniformed forces of the Central Government, State Governments or the Union Territories, while on metro railway in the course of their duty, may carry the authorized weapons, arms and ammunition.
