This article uses the term 'international legislation' to refer to the creation, by the Security Council, of norms by which the Council intends to bind all states, irrespective of their consent. The norms produced by the Council must in turn purport to modify some element of existing law, or to create new law, and they must be general in nature. Two resolutions of the Security Council emerge as 'legislative' under this definition: SCR 1373 of 2001 and SCR 1540 of 2004. Relying on the legal philosophy of Lon Fuller, this article will argue that these resolutions do not, in fact, produce law. Under Fuller's approach, the formal source of a norm is insufficient to determine that norm's legal status, as law is instead constituted by characteristics internal to the normative system. This article sets out these characteristics, analyses them and suggests how they might apply to the international setting. It argues that a practice of legality, in Fuller's terms, arises from three basic elements: reciprocity between the law-giver and those affected by the law; congruence between stated norms and exercises of public authority; and a respect for, and reliance on, the agency of those affected by the norms of the legal system. The article demonstrates that even formally valid activity has failed to attain the status of law because it has not followed these basic elements. It then argues that the Security Council is generally prevented by its very institutional structure from creating norms around which a practice of legality could emerge.