The cornerstone of the EU has been the open border agreement. The Schengen agreement is how they eliminated the need for passports to cross every border in the EU. But now they aren’t happy with that because folks on the exterior – specifically Greece – are not enforcing border security. So no one has border security. Greece is back at the heart of EU’s existential crisis with threatened expulsion from Schengen
Greece is being threatened with expulsion from Schengen. That is, you would no longer be able to travel from Greece to any other EU country without a passport.
This is in response to their refugee crisis.
Britain is trying to renegotiate their agreement with the EU, and if they can’t the Prime Minister is threatening to lead the campaign to get the UK out of the EU.
The dream of European unity seems to be shattering at its weakest points.