Professor Gavin Barrett an expert in EU law at University College Dublin said that the EU could not function effectively without the supremacy of its laws being accepted.
He told The Telegraph: “Much of the power of the European Union derives from EU law operating uniformly and effectively right across the territory of all 27 Member States.
“Take that away and each Member State turns into a separate legal zone where the rules on say, the Single Market, and criminal justice cooperation differ from one place to the next.
“In other words, you end up with no unified legal system, no Single Market, and in effect a crippled European Union. In its own way this development is a crisis of greater significance than Brexit has ever been.
“The EU has survived Brexit. But if the view becomes widespread that supremacy no longer holds sway in national courts, then the EU won’t survive – at least not in its present form.”
All EU member states have to agree to a treaty provision that EU law overrides national law.
According to membership treaties the European Court of Justice (ECJ) in Luxembourg is the final arbiter.
Under the Romanian constitution the supremacy of EU law is accepted.
Referencing a similar dispute with Germany he said that the EU would have to go down the legal route if Bucharest couldn’t provide assurances that the supremacy of the EU would be accepted.
He said: “We have received a reaction from the Romanian government saying, ‘No, we want to have full respect of primacy… but in the framework of the Romanian constitution.’
“So, it’s not exactly the answer that we have received from the German government, without any conditions.”