This chapter examines the debate held in the early to mid-2000s on the remit of the United Nations Security Council to mandate legislative measures under Security Council resolution 1540 and how implementation of the resolution by states since has shed further light on such a remit. It argues that the General Assembly and Security Council consultative debates prior to adoption of resolution 1540 assured the legitimacy of resolution 1373 and suggest that the Security Council had evolved for its quasi-legislative role to become accepted by member states. The absence of war and military conflicts amongst states does not in itself ensure international peace and security. The non-military sources of instability in the economic, social, humanitarian and ecological fields have become threats to peace and security. Additionally, the Security Council has increasingly conducted thematic debates over the past few years, often featuring initiatives by monthly rotated Security Council presidencies.