It is unrealistic to think that Scotland will leave the Union without the consent of Westminster. This makes the key question a political one, which the courts cannot resolve.
Scotland’s only viable path to independence is by agreement with the rest of the UK. Therefore it all comes back to a political question: whether Scotland still has the right to leave the Union, and if so, how. As far back as 2002, in their masterly study of the modalities of Scottish independence, Jo Eric Murkens, Peter Jones and Michael Keating wrote of a ‘Catch 22 situation whereby the UK Government publicly recognises Scotland’s entitlement to independence and to hold a referendum but does not in practice provide the constitutional mechanisms to give effect to those rights, rendering them futile’.
Since then, Westminster has of course given effect to those rights with the 2014 referendum. But before the 2021 election, UK ministers were ruling out doing so again in any and all circumstances for decades to come. That approach has softened. But there is still no light shed under what circumstances a second vote could happen. The Secretary of State for Scotland, Alister Jack, seemingly invented some criteria in a late summer media interview, but it’s unclear as to whether this was interview rhetoric or a change in policy. (And since ridiculed by Johnson’s Downing Street Spads: Ed).
Fundamentally, there is a question which goes to the heart of whether the Anglo-Scottish Union remains one upheld by consent, which in turn is part of a wider question of what this redesigned, post-Brexit union is going to look like. This is a political question which not just should not be settled by the courts; it cannot be.