The Aligarh Police has invoked the stringent National Security Act against four people arrested in connection with anti-CAA protest in the city in February, officials said on Saturday. Aligarh SSP Muniraj G. said the NSA order was handed over to the four in jail on Friday night. The four have been identified as Imran, Anwar, Sabir and Faheemuddin. They are presently in jail and their bail application is pending before a sessions court.