Few court cases in the history of European integration have been more controversial than the decisions of the Court of Justice of the EU and the German Federal Constitutional Court on the European Central Bank's public sector asset purchase programmes. This article regards consistency and coherence in the case law as uncontroversial minimum conditions that have to be satisfied for the decisions to gain legitimacy. It assesses the case law against this benchmark and determines the limits of asset purchase programmes under a consistent and coherent application of the legal tests developed by the courts.