When it comes to the EU, there are various theoretical paradigms, including federalism, (neo)functionalism, (neo)institutionalism, intergovernmentalism.
Which theoretical model best describes the organization and functioning of the EU?
as you answered, I would differ the organization and the function of the EU. as the economic crisis has shown, and the immigration crisis is now showing us, the liberal intergovernmentalism is still alive from the functional perspective.
on the other hand, the question of institutionalism and constitutional set up, we can say that post-functionalism (see Schimmelffening) is a prevailing concept in the organizational understanding.
There is another book by Antje Wiener and Thomas Diez "European Integration Theory". I have not read it but Antje is very respected on the subject (and the same is probably true for Prof. Diez but I don't know him personally).
I'd propose a pragmatic approach, but be aware that both federalism and intergovernmentalism are misleading. In intergovernmentalism the European Council, hence the Member States, have the decision power. In issues for which the Commission and/or the European Parliament have the decision power we would talk about federalism. Hence the EU is something like a hybrid.
Thank you all for your valuable suggestions. As I can infer, when it comes to the EU the most difficult aim is to define it and theoretically label the organization.
The question you mentioned and described by the prism of federalism umbrella in pure EU context is very interesting perception. By its side 'foedus' is very complex, multidimensional phenomenon and concept.
If we perceive its essentials it seems clear that the very core of this paradigm fit the attempt to ensure the art of accommodation of the different cultures and identities. To my understanding, the EU is not pure explicit but implicit exemplar. In this insight, I will offer you some to my perception, valuable sources and literature to rethink about intergovernmental federal dimension in the European reality.
Intergovernmental Cooperation Rational Choices in Federal Systems and Beyond
NICOLE BOLLEYER COMPARATIVE POLITICS SERIES Oxford University Press 2009
Federalism and the Market Intergovernmental Conflict and Economic Reform
in the Developing World ERIK WIBBELS University of Washington Cambridge University Press 2005
I conducted research on European Regional Integration Theory and I am quite familiar with various approaches to the occurrence of this phenomenon. I can assure that they all have their merit and there is not one single approach that explains all the caveats, mechanisms, institutions and development of the EC/EU.
Having said that, two of the most used and debated theories are Liberal Intergovernmentalism and Supranational Governance. The former was mainly developed by Andrew Moravcsik and you can read the whole of the theory in his major book "The Choice for Europe". The latter was developed by Alec Stone Sweet, Wayne Sandholtz and Neil Fligstein, and you can read their theory in two books: "European Integration and Supranational Governance" and "The Institutionalization of Europe".
There are also shorter articles that explain their theories in various journals, specially the Journal of Common Market Studies.
So you can get familiarised with the theories, I also recommend you to read "European Integration Theory" by Antje Wiener and Thomas Diez. (On a personal note, I met Antje once when she came to the University of Birmingham to deliver a talk on the book. She's a great scholar! Thomas Diez also worked at some point at the University of Birmingham, where I studied. Finally, in a strike of luck, Wayne Sandholtz works at USC, where I am currently a Postdoc) :)
I recommend you to look for and use this book as an introduction to the theories, and once you have familiarised with them, look for journal articles written by Moravcsik, Stone Sweet, Sandholtz, Fligstein and Rosamond. And if you're very keen on European Integration Theory, go on to the quite heavy books I mentioned above.
I hope you find these theories of your interest. They all seem quite complex at the beginning, but you'll see that their core mechanism to explain the functioning and evolution of the EC/EU can eventually be summarised in some paragraphs. It's all quite exciting really! My whole PhD was about those theories.
I hope this was helpful. Do not hesitate to contact me if you have any other questions.
In the light to perceive the very recent developments in the field of Federalism and Regionalism I also recommend you the newest publication of International Idea.
Annual Review of Constitution- Building Processes: 2014 Lead writers and editors:
Melanie Allen, Elliot Bulmer, Tom Ginsburg, Jason Gluck, Yasuo Hasebe
Yuhniwo Ngenge, Roberto Toniatti,
Contributors: Richard Albert, David Landau, Kimana Zulueta-Fülscher
International Institute for Democracy and Electoral Assistance 2015
I hope you find some interesting case studies and materials here regarding recent trends worldwide.