The decision by Germany’s Federal Constitutional Court on May 5 hit the Eurozone institutions like a bomb. The European Central Bank (ECB) had just started to ramp up its purchase of sovereign debts to fight the coming COVID-19 economic crisis when Germany’s highest court questioned the legality of the ECB’s main asset purchase program — the Public Sector Purchase Programme (PSPP) that started in 2015.

Specifically, the court asked the ECB to justify its program to the German government and parliament within three months. The ECB must demonstrate that the economic impact of the bond purchases is proportionate to the objectives set out in the ECB’s founding treaties. If German political institutions believe that the ECB is exceeding its prerogatives, then the Bundesbank (the German central bank) is obliged to withdraw from the PSPP. All German government bonds purchased under it would then have to be sold again.

With their ultimatum, the German judges are not just questioning the ECB’s previous rationale for its bond repurchasing programs. They’re also contradicting the assessment of the European Court of Justice (ECJ), which had found the programs to be in conformity with European treaties. This raises two questions: Has the ECB exceeded the scope for action set by these treaties? And who is authorized to judge its actions? The answers to these questions will determine the ECB’s ability to deal with the coming economic crisis — and maybe whether European integration even has a future.