It also seems to have been forgotten that the GCC ruled, among others, on something which is none of their business. They ruled that the buying of sovereign bonds in secondary markets on the part of the ECB was not compatible with EU-laws. That would be an issue for the European Court of Justice (ECJ) and I have written about that here. The GCC would have to transfer the issue to the ECJ and ask for a ruling.
It seems that the Irish member of parliament Thomas Pringle has jumped the gun on the GCC. Mr. Pringle has challenged the constitutionality of the ESM before the ECJ and a ruling is expected by the end of the year.