Resolution 1540 is a notable development both in that it explicitly recognises non-state proliferation of weapons of mass destruction as a threat to peace and security in and of itself and in that it obliges member states to make internal legislative changes. Previous non-proliferation agreements all took the form of multilateral accords such as the Nuclear Non-proliferation Treaty or cooperation mechanisms such as the Proliferation Security Initiative, based on the consent of the parties. Resolution 1540, on the other hand, is obligatory for all UN members, whether or not they support its aims.