The relationship between EU law and German constitutional law, and the respective dialogue between the ECJ and the German Federal Constitutional Court (FCC), have considerably shaped the EU integration process by creating fields of tension and demarcating possible legal boundaries. The decisions of the German Federal Constitutional Court and the European Court of Justice concerning the European Stability Mechanism are only the most recent examples of this phenomenon. These developments have, of course, spilled over to other EU Member States. The German constitutional bases of, and limits to, EU integration—especially as articulated in the relevant decisions of the German Federal Constitutional Court—have therefore become a field of particular interest for EU and public lawyers. This article gives an up-to-date overview of relevant constitutional rules, court decisions, and the academic debate in Germany. It does so by systematically distinguishing between an analysis of the German constitutional foundations of EU integration (section B.), constitutional limits to the further transfer of powers to the EU through amendments of EU primary law (section C.I.), and the constitutional confines for the legal effects of EU secondary law in Germany (section C.II.).