What I do find is this:

EUR-Lex - C2010/083/01 - EN - EUR-Lex

Article 130

(ex Article 108 TEC)

When exercising the powers and carrying out the tasks and duties conferred upon them by the Treaties and the Statute of the ESCB and of the ECB, neither the European Central Bank, nor a national central bank, nor any member of their decision-making bodies shall seek or take instructions from Union institutions, bodies, offices or agencies, from any government of a Member State or from any other body. The Union institutions, bodies, offices or agencies and the governments of the Member States undertake to respect this principle and not to seek to influence the members of the decision-making bodies of the European Central Bank or of the national central banks in the performance of their tasks.

Article 131

(ex Article 109 TEC)

Each Member State shall ensure that its national legislation including the statutes of its national central bank is compatible with the Treaties and the Statute of the ESCB and of the ECB.

And this:

The Statute of the European System of Central Banks and of the ECB

Article 14
National central banks
14.1. In accordance with Article 131 of the Treaty on the Functioning of the European Union, each Member State shall ensure that its national legislation, including the statutes of its national central bank, is compatible with these Treaties and this Statute.

14.2. The statutes of the national central banks shall, in particular, provide that the term of office of a Governor of a national central bank shall be no less than five years.

A Governor may be relieved from office only if he no longer fulfils the conditions required for the performance of his duties or if he has been guilty of serious misconduct. A decision to this effect may be referred to the Court of Justice by the Governor concerned or the Governing Council on grounds of infringement of these Treaties or of any rule of law relating to their application. Such proceedings shall be instituted within two months of the publication of the decision or of its notification to the plaintiff or, in the absence thereof, of the day on which it came to the knowledge of the latter, as the case may be.

14.3. The national central banks are an integral part of the ESCB and shall act in accordance with the guidelines and instructions of the ECB. The Governing Council shall take the necessary steps to ensure compliance with the guidelines and instructions of the ECB, and shall require that any necessary information be given to it.

14.4. National central banks may perform functions other than those specified in this Statute unless the Governing Council finds, by a majority of two thirds of the votes cast, that these interfere with the objectives and tasks of the ESCB. Such functions shall be performed on the responsibility and liability of national central banks and shall not be regarded as being part of the functions of the ESCB.

But hey, it is all in the interpretation, and the EU has a lack of gunboats to enforce interpretations.

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