References to settled case law permeate the decisions of the European Court of Justice. Legal literature commonly deems them elements of stability and constraint. By contrast, this article highlights their transformative effect. That effect occurs in the process of repetition, conceptualized as a process that permits alteration. The article identifies and explores three types of alteration, or three mechanisms of instability: (1) the substitution of cited cases in citation strings; (2) the alternation between expressions found in settled case law and alternative expressions; and (3) the un-anchoring or detachment of legal statements from cases in which they initially appeared. The analysis illustrates how substitution leads to diverging interpretive outcomes, how alternation unsettles the normative force and the relevance of the acquis, and how un-anchoring results in a loss of knowledge. From this perspective, references to settled cases result in complex changes to the law – changes which are multi-directional and lack a clear progression. The article contributes to a better understanding of legal change, and it illuminates the role of past cases in the Court’s decision making.