The various Institutions
of the European Union owe their existence to the existing European Treaties - principally the Treaty on European Union (TEU) - see the Consolidated versions of the Treaties. The powers and the duties of each Institution are also to be found in these Treaties.
Thus, the basic role of the Commission is to promote the general interest of the Union and take appropriate initiatives to that end" and to "ensure the application of the Treaties" - TEU Art 17. The general role of the Court is set out in TEU Article 19(3) - "The Court of Justice of the European Union shall, in accordance with the Treaties: (a) rule on actions brought by a Member State, an institution or a natural or legal person; (b) give preliminary rulings, at the request of courts or tribunals of the Member States, on the interpretation of Union law or the validity of acts adopted by the institutions; (c) rule in other cases provided for in the Treaties."
Hence, the role of the Institutions is not only defined by the European Treaties but is limited by those Treaties and it would be unlawful for an Institution to operate beyond the powers granted to it by the Treaties.
The interesting question arises - may a new compact between EU member States other than the UK confer additional powers on the EU Institutions without amendment of the European Treaties?
The procedure for amending the existing European Treaties is to be found in TEU Art 48. There is an ordinary revision procedure and a simplified revision procedure. The latter applies to Part 3 of the Treaty on the Functioning of the EU (TFEU). (Part 3 TFEU deals with the internal policies and actions of the EU).
Amendments to the Treaty on European Union (TEU) would require use of the "ordinary revision procedure" which requires that amendments enter into force after being ratified by ALL member states in accordance with their respective constitutional arrangements - Art 48(4). (My emphasis]. Hence, amendment of the TEU appears to be impossible without the agreement of the UK and the TEU is, of course, the source of the powers of the EU Institutions.
However, Article 48 provides that if, two years after the signature of a treaty amending the Treaties, four fifths of the Member States have ratified it and one or more Member States have encountered difficulties in proceeding with ratification, the matter shall be referred to the European Council.
Hence, may the new compact (once concluded) confer additional powers on the EU Institutions without amendment of the European Treaties? Given that the powers of the Institutions exist only because of the EU Treaties, my very tentative answer would be "NO". Amendment would have to be ratified by all member states including the UK and without this, the purported amendments would not be in compliance with TEU Art 48.
Of course, I am not suggesting that the UK will necessarily refuse to go along with any amendments put forward in the compact. Perhaps the UK government will opt to consider each and every proposed amendment to the existing treaties on its merits. A further issue is that amendments to existing treaties might trigger the referendum requirement in the European Communities Act 2011.
There are already some situations - e.g. Schengen Accords - where not all EU member States are fully aligned. However, all the EU states have been prepared to go along with these arrangements. They seem to differ markedly from the position reached at Brussels on Friday 9th December where one member state (UK) is completely at odds with the others.
This "interesting question" may prove to be difficult and the above is a very tentative view. How things will develop will be a major issue in the next few weeks and months. Comments as ever are welcome.
Addendum 13th December: According to an item in The Guardian, the UK will not seek to prevent other EU member States using the EU's institutions in relation to the compact - "EU summit veto recriminations mount within coalition" - The Guardian 12th December. The Telegraph took a look at the financial situation following the UK's opt out - "City not shielded by Cameron's veto, EU insists"