According to the EU Parliament, the ECB "does not have the competence to adopt the Addendum because it defines mandatory legal rules of a general purpose applicable to all banks supervised directly by the ECB".
Brexit, EU Parliament approves resolution

The joint motion, which sets the benchmarks for the United Kingdom's exit from Europe, was supported by the groups of the EPP, S&D, Alde, Greens and the United Left - Among the priorities of the negotiation are the rights of European citizens, the protection of agreement of…