I think this is the point. All of these arrangements are ultimately by consent. Holyrood agrees to recognise Westminster's power, just as the UK agrees to recognise the ECHR.
This idea of 'power' is a complicated one. What 'power' does England have over Scotland other than the power that Scotland has agreed to accept (see Northern Ireland for what happens when one of the devolved nations is conflicted over whether to accept that power)? What 'power' does the ECHR have over any of its signatories other than that which they've chosen to accept?
There's a well-written and detailed exploration of the negative consequences of withdrawing from the ECHR here, and what is power except the ability to impose negative consequences for not following instructions?
This idea of 'power' is a complicated one. What 'power' does England have over Scotland other than the power that Scotland has agreed to accept (see Northern Ireland for what happens when one of the devolved nations is conflicted over whether to accept that power)? What 'power' does the ECHR have over any of its signatories other than that which they've chosen to accept?
There's a well-written and detailed exploration of the negative consequences of withdrawing from the ECHR here, and what is power except the ability to impose negative consequences for not following instructions?
https://verfassungsblog.de/uks-potential-withdrawal-european...