The ideas of the culture of justification – according to which it is the role of the courts to ensure that every act of the state that affects a person is substantively justifiable – and the related right to justification – which claims that every person possesses a moral and, ideally, constitutional right to the justification that the culture of justification recommends – are intuitively powerful and widely discussed ideas in public law scholarship, but their moral foundation is not yet well understood. This paper presents the moral case for these two concepts which centres on the status of every person as a justificatory agent. It argues that under conditions of reasonable disagreement in politics, this status requires that any law or act be justified not only procedurally (for example, in terms of a democratic vote) but also substantively, and it further demonstrates the necessity of the judicial protection of the right to justification as a matter of principle.