The European Court of Justice could overrule any Brexit deal made between the UK and Brussels, MPs have been told.
Konrad Schiemann, who formerly represented Britain on the court, told the Commons Brexit select committee yesterday that if even if both sides reached an accord they could still be forced back to the negotiating table by the ECJ.
The court may also insist on a continuing role in policing any future agreement between the EU and the UK, he noted, which would cross one of the critical red lines set out by the government.
“Any agreement that is made between the EU and parliament is subject to challenge in the European Court of Justice on the subject of powers of the parties who have made that agreement,” Schiemann said.
“The Commission and the people negotiating on behalf of the EU are faced with this problem: they can’t just do what they think is good. They have got to remain within their powers.”
Schiemann said the ECJ could "certainly" challenge withdrawal terms "so far as they touch on the role of the ECJ", noting that for non-ECJ matters it was less clear-cut.
"If you exclude the ECJ altogether and for example try and set up a different tribunal — this has been done in various other draft treaties — sometimes the ECJ has said yes that will work and other times it has said it won’t," he said.