Has there ever been a time when the EU has devolved power back to the nations within it?
I can't ever recall something like that happening. But every decade or so there's a new EU treaty that transfers more power to the EU, eventually you end up with something that looks like the EU as the country and the old nation states as the provinces, but it happens so slowly over time that nobody really stops and asks if that's what everyone wants.
In France they did ask.
In 1992 there was a referendum about Maastricht, where the 'yes' had a tiny lead over the 'no'. In 2005 the French people voted a resounding 'no' to the European consitution , so did the Dutch if I remember well.
EU then modified minor things and renamed it the Lisbon treaty, which has been ratified by parliamentary procedure.
So even when people opinion is being asked, it's completely circumvented.
It is very clear that EU has never been about building a democracy, those that believe that are very naive.
I can't ever recall something like that happening. But every decade or so there's a new EU treaty that transfers more power to the EU, eventually you end up with something that looks like the EU as the country and the old nation states as the provinces, but it happens so slowly over time that nobody really stops and asks if that's what everyone wants.