Amidst the first wave of the coronavirus pandemic, the German Federal Constitutional Court rendered a little-noticed, but potentially far-reaching decision regarding European integration. When it declared the law ratifying the Unitary Patent Court Agreement unconstitutional, it did so because it is a treaty “supplementing or being otherwise closely tied to the EU”, in other words, a satellite treaty, inter-se agreement, or more generally: an international law agreement furthering European integration outside the EU law framework. This commonly used integration technique is therefore going to be a lot more difficult in future whenever Germany is involved. At the same time, the court order gives all German citizens a far-reaching right to have laws ratifying such treaties checked before the Constitutional Court, which is a significant extension compared to its earlier case-law. In future cases of disagreement, EU Member States may have to find different ways to proceed than resorting to international law, such as using the enhanced cooperation mechanism.