Last week the top Scottish court allowed a selection of MSPs, MPs and MEPs to ask an important question. The question, in short, is: where a member state has served notice of intention to withdraw from the EU, can that notice be unilaterally revoked and, if so, on what conditions and with what effect? They needed the permission of a court to ask that question of the Court of Justice of the European Union (“CJEU”). That permission was granted.

The case (Wightman MSP and others v Secretary of State for Exiting the European Union [2018] CSIH 62) discusses a number of important points about the relationship between the courts and parliament, and whether the courts will address hypothetical questions. It is compulsory reading for lawyers. For everybody else, why does this case matter?

The answer is this: there is real, and apparently increasing, support for a second referendum on whether Brexit should happen. Whatever your views, it is an issue that won’t go away. Or will it?

If the CJEU comes back and says that, yes, the UK can withdraw its application to leave, and does not need anybody else’s permission, then it may give encouragement to supporters of another referendum.

If, however, the CJEU comes back and says the opposite - no, the UK cannot withdraw its application unilaterally, then that will be a game-changer. As we now know, getting the 27 states, or even a majority of them, to agree on anything is at best a long process, at worst impossible. If their consent is needed, then the realpolitik is that seeking a second referendum to persuade the UK public to change its mind becomes almost pointless.

The process would require (a) the agreement of the UK Parliament to hold a second referendum, against an already tight deadline of 29 March 2019; (b) holding a second referendum, with the uncertainty, delay, expense and ill-feeling that might involve; (c) recognising that the second referendum may result again in a “leave” vote, thereby wasting that time and expense; (d) accepting that a “remain” result is not the end of the process. If, after all that, consent of the EU is needed (in whatever form that may take), then the chances of successful revocation prior to the Brexit deadline appear to be vanishingly small.

The CJEU is the final judge of questions of EU law. This question could not be finally answered by a UK court. The Scots have set the ball rolling.  Whether the ball can be caught by the CJEU and thrown back in time for it to make a political – and not just a legal – difference is entirely another matter.

First published in The Times on 25 September 2018.