The constitutional justification for the principle of legality has been transformed. Its original basis in a positive claim about authentic legislative intention has been repudiated. The contemporary dominance of statutory law exposes descriptive error in supposing any improbability in legislative intentions to abrogate common law rights. Two rival justifications for the principle have emerged in response. One is a refined positive claim: legislatures do not intend to abrogate ‘fundamental’ rights. Another is a normative claim: courts should attribute an intention not to abrogate rights in order to improve the political process. Distinguishing these justifications answers the vexed question of which rights engage the principle of legality. Fundamentality, in the first claim, takes content from its justificatory function. The normativity of the second claim implies engagement not by ‘fundamental’ rights, but by ‘vulnerable’ rights. ‘Vulnerable’ rights may originate not only in the common law but also in statutes.