Does Westminster really have control over staging an independence referendum?

Nicola Sturgeon is to seek a Section 30 order before Christmas from the new Prime Minister to enable a transfer of power from Westminster in order to allow a referendum on Scottish independence. But does she need to?

Her priority is to find a political agreement on the issue. But if the Section 30 request is refused, the First Minister and her Constitutional Affairs Secretary Michael Russell have hinted that a legal challenge could be looming.

Ms Sturgeon told radio listeners yesterday that the matter has "never been tested in court."

It is widely acknowledged that control over the constitution is reserved to Westminster, but would this prevent Holyrood from staging a legally sound vote on the matter?

Nicola Sturgeon wants an independence referendum next year

The Scotland Act, which brought about devolution 20 years ago makes no mention of referendums. Following the principle that any issue not clearly reserved is, by default, devolved it could be argued this falls into Holyrood's realm. Particularly given that the legislation, at roughly the same time, which brought about the devolved assemblies in Wales and Northern

Ireland did make it clear that the authority of Stormont and Cardiff to hold such votes was restricted.

If a court took the view that any referendum was only a test of public opinion which did not materially or legally affect the union itself - and did not therefore breach the terms of the Scotland Act - Ms Sturgeon may have a case.

This is indisputably reserved and would require co-operation from Westminster. It may then seem a futile exercise to stage a referendum under such a scenario. But it's worth remembering that all referendums are only advisory, not legally binding. This was the case with Brexit and even with the 2014 independence vote. The Edinburgh Agreement signed by David Cameron and Alex Salmond was only a political accord.

Legally, had Scots voted for independence, Westminster retained the legal authority to disregard the outcome.

If Nicola Sturgeon feels there is little prospect of making progress with an intransigent Tory Government on the prospect of a transfer of power for a second referendum, perhaps her hand will be forced to make something happen and appease hardline supporters.

And after the UK Supreme Court stepped into overrule the prorogation of the Commons earlier this year, a move spearheaded by the SNP's Joanna Cherry, resorting to legal challenge no longer seems an unprecedented approach to resolve political disputes.