Herve, my opinion is that you can sue anyone for anything (think America) but a case against a member of the EC wouldn’t succeed unless you could prove negligence, fraud or other ‘bad faith’ actions by that EC member.
As the onus of proof is on the person bringing the action, knowing a person did wrong and proving it are often worlds apart.
I have seen a lot of people start legal cases on ‘principle’ and then realise the financial realities are that they just should have accepted that they were duped and that as hard as it was they should have just moved on.