This week’s supreme court hearing in London about article 50 of the Lisbon Treaty considered fundamental arguments about the centuries-old balance of power between the executive and Parliament.
It also heard arguments about how devolution may have shifted sovereignty away from Westminster and about the implications of Brexit for the constitutional settlement in Northern Ireland.
The supreme court justices avoided, however, what could be the most politically significant question about article 50: whether it is irrevocable once Theresa May triggers it, as she has promised to do before the end of March next year.
Both sides in the argument before the supreme court accepted that article 50 could not be revoked, and the court operated on that assumption.
Experts are divided on the issue, however, with John Kerr, a British diplomat who helped to draft the article, insisting that it can be revoked if the British government changes its mind about leaving the EU.
“It is not irrevocable. You can change your mind while the process is going on. During that period, if a country were to decide, actually, we don’t want to leave after all, everybody would be very cross about it being a waste of time. They might try to extract a political price but legally they couldn’t insist that you leave,” he told the BBC last month.
Brexit secretary David Davis suggested this week that MPs will get a vote on the final deal that emerges after withdrawal negotiations with the EU, which could take two years.
No deal
Such a vote would be of little value, however, if article 50 cannot be revoked, as MPs would have to choose between accepting the deal or allowing Britain to leave with no deal at all.
The legal stratagem chosen by Jolyon Maugham QC and others to establish whether article 50 is irrevocable is, at first sight, bewildering. By accusing the Irish State, the European Commission and the European Council of breaching EU law, they hope to force the issue onto the agenda of the European Court of Justice.
An Irish court could baulk at the prospect of being used as an instrument to resolve what might be seen as an internal political dispute within Britain. But Maugham argues that Ireland’s interests will also be served by having the terms of article 50 clarified.
“This is not a good moment for anybody. There are people over here who want to leave the EU who care very much about the impact upon the Republic. There are people who want to remain who care very much about the impact upon the Republic. We all are mindful of the need to secure that the interests of the people of Ireland are affected as little as possible,” he said.
‘Breach of treaties’
“But if there has been a breach of the treaties by the
Irish Government
, and I’ve been advised by Irish senior counsel that there has, then I have to say it’s perfectly proper for me to seek a remedy for that breach in the Irish courts.
"And if it should happen to deliver a situation where our parliament is better able to secure a Brexit that helps the United Kingdom and helps Ireland, then that's something that people should welcome."