Additionally, a crisis management tool, the European Stability Mechanism, was created as an intergovernmental body outside the Treaties. At the same time, a banking union was set up with a single supervisor, a single resolution authority and a still-to-be-completed single deposit guarantee scheme.
According to an empowering clause included in the Maastricht Treaty activated by unanimity, the ECB received specific supervisory powers, albeit only for credit institutions. This transfer of sovereignty is still being challenged in the German Constitutional Court.