Preventive police action is necessary to avert cognizable offences and protect public order, but it must operate within constitutional limits. This paper examines Sections 168–172 of the Bharatiya Nagarik Suraksha Sanhita, 2023, which address prevention of cognizable offences, communication of information, preventive arrest, protection of public property and compliance with lawful police directions. It distinguishes these powers from preventive detention under separate legislation. The paper analyses Articles 14, 19, 21 and 22 of the Constitution and considers judicial decisions concerning arbitrary arrest, fair procedure, custodial safeguards and peaceful assembly. It argues that preventive action must rest on credible grounds, be necessary and proportionate, and remain subject to documentation, accountability and judicial review. Effective prevention of crime and protection of personal liberty are complementary obligations in a constitutional democracy.