Point: One view is that devolution has put the Union at greater risk by giving Scotland the political base from which to push for independence.
Example: The Scottish independence referendum in 2014 returned a 55-45 No vote, the closest the Union has come to formal break-up in modern times.
This shows: Critics argue that without devolution there would have been no Scottish Parliament from which to launch a credible independence campaign.
However... However, the headline outcome of the referendum was a clear No.
Counter example: Scotland voted to remain part of the United Kingdom by ten percentage points. In the eleven years since, no further independence referendum has been held, and no UK government has approved one.
This shows: This shows the headline test of the Union - whether it survives a direct popular vote on independence - has been passed.
Interim judgement: On the test that matters most, devolution has not put the Union at greater risk: when asked directly in 2014, Scottish voters chose to stay.
Point: Some argue that devolution to Northern Ireland creates fresh constitutional risks because the NI Assembly has been repeatedly suspended.
Example: The NI Assembly was suspended from 2022 to 2024 over disputes about the Northern Ireland Protocol, with the DUP refusing to nominate a deputy First Minister.
This shows: Critics argue that an institution that does not function for years at a time cannot be called a success.
However... However, the test of NI devolution is not whether the Assembly always works.
Counter example: Throughout the 2022-24 suspension, there was no return to the violence of the Troubles. The Assembly was restored under the Stormont Brake compromise without significant political damage to the wider Union.
This shows: This shows that the basic settlement created by the Good Friday Agreement 1998 has absorbed the post-Brexit constitutional shock without breaking.
Interim judgement: On the most important test - whether Northern Ireland remains peaceful and part of the UK - devolution has not put the Union at greater risk.
Point: A linked argument is that asymmetric powers, including Scotland's ability to set its own income tax, create divergence that pulls the Union apart.
Example: Under the Scotland Act 2016 Scotland has used its tax-setting power to maintain a slightly higher rate on higher earners and to fund free university tuition.
This shows: On this reading, growing policy divergence makes the Union increasingly hard to hold together.
However... However, divergence is what the settlement was designed to allow.
Counter example: The Scotland Act 2016 was passed by Westminster after the 2014 referendum specifically to deepen devolution rather than reverse it. The political bargain was that increased autonomy would reduce independence pressure, and on the headline measure it has.
This shows: This shows divergence is not a sign that the Union is failing: it is how the Union was designed to work after 1999.
Interim judgement: Far from putting the Union at greater risk, the Scotland Act 2016 demonstrates that the Union can flex to absorb new demands without breaking up.
Point: A strong case for the risk argument is the use of Section 35 in 2023 to block the Scottish Parliament's Gender Recognition Reform Bill.
Example: In 2023 the UK government used a Section 35 order for the first time to block a Scottish Bill, escalating the dispute into a constitutional confrontation between Holyrood and Westminster.
This shows: Critics argue that Section 35 has shown how easily devolved disputes can become Union-level constitutional crises that fuel independence sentiment.
However... However, the political consequence has been modest.
Counter example: The Section 35 order was challenged but ultimately accepted. The Scottish Parliament did not respond by leaving the Union or by holding another independence referendum. SNP support did not rise as a result.
This shows: This shows that even the sharpest constitutional collision between Holyrood and Westminster has not converted into renewed independence pressure.
Interim judgement: Section 35 is a strain on the settlement but not a strain on the Union itself: the political risk has not materialised.
Point: Finally, some argue that the unenforceable Sewel Convention shows the settlement is hollow and that the Union is held together only by Westminster goodwill.
Example: The Sewel Convention - that Westminster will not normally legislate in devolved areas without consent - has been overridden in practice on Brexit-related legislation and is not enforceable by the courts.
This shows: On this reading, the legal weakness of the convention shows the Union rests on shaky foundations.
However... However, what looks like weakness is also flexibility.
Counter example: No Westminster government has used its legal sovereignty to abolish the devolved bodies, and no devolved body has tried to declare independence unilaterally. The convention has held politically even when it has bent legally.
This shows: This shows the settlement runs on political restraint rather than legal rigidity, which is the normal pattern in a quasi-federal system.
Interim judgement: On balance, devolution has not put the Union at greater risk: the absence of legal entrenchment has been a feature, not a flaw, allowing the settlement to absorb shocks without breaking.