The UK Supreme Court has resoundingly held that the UK Government may not serve the Article 50 notice withdrawing from the European Union without an Act of the UK Parliament giving the necessary parliamentary authorisation.
However, the decisive result (8:3 of the full 11 judge panel) may have limited political fallout in practical terms, given the position taken by Theresa May last week when she confirmed that the UK Parliament will have a vote on the terms of any Brexit deal negotiated. The likely outcome is a short-form Act, although the political theatre will no doubt be interesting.
However, buried in the detail, there are some interesting points. First, the court proceeded on the assumption that, once served, the Article 50 notice is irrevocable. This point was conceded by the UK Government. The reason for this concession was primarily political, as the legal question of whether or not the notice is revocable is a question of European law which would have to be decided by the Court of Justice for the European Union (CJEU). It would not be politically palatable for this UK Government to be seeking a reference to the CJEU!
Meanwhile, proceedings have been commenced in Ireland to seek a reference to the CJEU on precisely this point. A finding that the Article 50 notice was revocable by a Member State serving it, would change the negotiating dynamic. The UK could then, theoretically, say if it did not like the exit terms offered that it would revoke the notice and remain a member of the EU after all. Any such volte face would require a profound change in the political climate, but stranger things have happened. It remains to be seen whether, and at what speed, these Irish proceedings will progress.
The other point of Irish interest is the treatment of the various cases commenced in Northern Ireland. The court found that it did not need to express a view on whether the Northern Ireland Act separately required primary legislation to authorise service of the Article 50 notice. This is because of the conclusion it reached on the main question requiring primary legislation by the UK Parliament.
However, the court unanimously rejected the argument that the terms of the Northern Ireland Act required the consent of the Northern Ireland Assembly to any withdrawal from the EU. This view flowed from the clear terms of the Northern Ireland Act itself, which gives a right to the people of Northern Ireland to decide by poll whether they should cease to be part of the United Kingdom and form part of a united Ireland, but does not give them any rights in relation to membership of the EU.
The court also went on to hold unanimously that the Sewel Convention on the interaction between the UK Parliament and the devolved Assembly in Northern Ireland did not create legally-enforceable obligations because it was a convention only. The Sewel Convention provides that the UK Parliament "would not normally legislate" with regard to devolved matters except with the agreement of the Assembly. The devolution legislation stipulates that the devolved government of Northern Ireland must not act in breach of EU law, and therefore a change to that position (by withdrawal from the EU) is probably fairly regarded as legislation with regard to devolved matters.
However the court's view is that the consequence of ignoring the Sewel Convention by the UK Government must be political and not legal. It will be interesting to see the political consequence in Northern Ireland if the UK Government decides simply to ignore the operation of the Sewel Convention or contend that this is 'not a normal' situation.
Perhaps the most pointed comment in the majority judgment was the reference to proceedings before the House of Lords Select Committee in the period from 2009-2011. In its twelfth report, the Committee included the following recommendation:
"Because of the sovereignty of Parliament, referendums cannot be legally binding in the UK, and are therefore advisory. However it would be difficult for Parliament to ignore a decisive expression of public opinion".
The UK Government's response, as recorded in the Committee's fourth report of the session in 2010/2011 (then David Cameron's Government), was:
"The Government agrees with this recommendation. Under the UK's constitutional arrangements Parliament must be responsible for deciding whether or not to take action in response to a referendum result".
The UK Government's position in relation to these proceedings has of course been directly contrary to the position taken before the House of Lords Select Committee at that time. It has now been found to be wrong by its own court of final resort.