what happens if eu court of justice overturns eu council ruling?

Answer 1

I tried looking for a case where that happened, and the first one I could find was Brems v. Council, T-75/89. There the ECJ annulled a Council decision regarding the dependency status of an EU civil servant's child. The court basically remanded the matter back to the Council for reconsideration in light of the decision. I assume other cases follow the same route back to the Council for reconsideration.

Answer 2

Well, if the ECJ finds that the Council - or indeed any EU body has acted ultra vires (i.e. outside the powers conferred upon it contrary to Art 5 para 1 EC Treaty), or breaches the principle of subsidiarity in para 2 (that the EU should take action only when it cannot be sufficiently achieved by Member States and can therefore by reason of scale or effects of the proposed action be better achieved by the Community), or indeed breaches the principle of proportionality in para 3, or indeed breaches the general principles of Community law such as acting contrary to citizen's legitimate expectations, then the purported act, decision, or regulation etc. is annulled and void. It does not have legal effect. It is like any public authority that acts contrary to the legislation conferred on it- the act is annulled and declared void; it is of no legal effect.

Answer 3

The ruling of the EU Court of Justice will be binding since it is an appellate body.