Politicians need to know all their options on Brexit, including whether the UK can unilaterally halt the process, a lawyer has argued in the European Court of Justice.
Aidan O’Neill QC is representing a cross-party group of politicians who launched the action to determine whether the withdrawal process triggered under Article 50 can be halted by the UK on its own, without prior consent of the other 27 EU member states.
Those who brought the case argue unilateral revocation is possible, while legal representatives for the UK Government said the case is inadmissible as it deals with a hypothetical situation.
The court also heard from lawyers representing the Council of European Union and from the European Commission, who both argue revocation is possible but would require unanimous agreement from all member states.
Giving evidence at the court in Luxembourg, Mr O’Neill said it is “fundamental” to the treaties of the EU that an individual member state can unilaterally revoke the decision to withdraw.
He said: “It cannot be in the interest of the union as a whole to force a member state to leave the union against the wishes of the people.
“The union’s wider interest lies with member states remaining in the EU when their peoples wish to do so.”
He accused the Council of the European Union and the European Commission of inviting the court to act “unconstitutionally and in contravention of the rule of law by reinterpreting the treaties”.
Mr O’Neill said the commission “misunderstands” and the UK Government “misinterprets” UK constitutional law.
He said the politicians who brought the case, “need to know the options for revocation, which are open to withdrawing member states now, to allow them, properly and in a fully informed way, to carry out their duties as democratically elected representatives, accountable to the people.”
Advocate General for Scotland Lord Keen QC, representing the UK Government, argued the question of whether or not Article 50 can be unilaterally revoked should be ruled inadmissible as it is a “hypothetical validity challenge” and asked the court not to open “this Pandora’s box”.
He said the UK Government does not intend to revoke Article 50 and later confirmed it has no position on revocation.
Mr Keen said what those bringing the case seek is “political ammunition to be used in and to pressure the UK Parliament”.
It was brought forward in February by a group Scottish politicians – Labour MEPs Catherine Stihler and David Martin, Joanna Cherry MP and Alyn Smith MSP of the SNP, and Green MSPs Andy Wightman and Ross Greer, together with lawyer Jolyon Maugham QC, director of the Good Law Project
Lord Keen added: “In short, they seek to co-opt this court into their ongoing political campaign in regard to an issue of almost unparalleled political controversy and sensitivity.”
He said this would be a constitutional anathema that would pose an unprecedented threat to parliamentary privilege.
Hubert Legal, representing the Council of the European Union, said allowing unilateral withdrawal could lead to “disaster”, of which “the main victim could be the European project altogether”.
He said Article 50 is “not ambiguous”, adding: “The prerogative of acting alone will have been exhausted by putting the notification letter on the council’s table.”
The ECJ is the highest court in Europe regarding EU law and a written judgment on the case is expected in the coming weeks, with the president of EJC saying it will happen “quickly”.
Scotland’s most senior judge Lord Carloway ruled in September to refer the question to the ECJ after the case was heard at the Court of Session in Edinburgh, Scotland’s highest civil court.
UK Government attempts to appeal against this ruling were rejected by the Court of Session and the Supreme Court.
In its ruling last week, the Supreme Court stipulated the Court of Session will have to reach a judgment on the matter after the ECJ has given guidance.
Alyn Smith MEP said the court would provide “important clarity which only they can give” and he is “very optimistic” about the outcome.
He said: “I think it paves the way for other ways out. I think the People’s Vote is one of those things.
“A second EU referendum, a meaningful vote in the House of Commons instructing Theresa May to revoke Article 50 letter – there’s other ways in which this could be fixed, it’s not about a false choice between Mrs May’s deal or chaos. There are other ways out this.
“What this ruling will give when we see it, and I think today was very positive for that, will be identifying the road map out of Brexit.”