By Elisabeth O'Leary
EDINBURGH (Reuters) - The governments of Scotland and Wales say they cannot consent to a UK-wide parliamentary bill on withdrawal from the European Union, arguing that the bill would strip back the powers of their devolved parliaments.
Their devolved powers do not allow them to stop the Brexit bill, currently going through the central UK parliament in London, where the pro-Brexit Conservative government has a working majority. But it could lead to a constitutional crisis.
The UK, a union of England, Scotland, Wales and Northern Ireland, has a central parliament at Westminster in London which legislates for the entire UK, and three devolved parliaments in Edinburgh, Cardiff and Belfast, to which different powers have been meted out under what is known as the devolution settlement.
The complex relationships between the four nations have been destabilised by the 2016 EU referendum, in which England and Wales voted for Brexit while Scotland and Northern Ireland voted to remain in the EU.
CAN SCOTLAND VETO BREXIT?
Scottish politicians acknowledge that it cannot, including Scotland's Brexit minister Michael Russell on Tuesday.
"This bill is not an opportunity to veto Brexit: such a legal power does not exist," he said.
SO WHAT'S THE PROBLEM?
Under Britain´s constitutional mechanisms, the UK parliament must seek consent from the Scottish parliament and the Welsh assembly when legislating on a policy area that overlaps with their domestic powers.
The Brexit bill does not directly concern devolution, but the Scottish and Welsh governments -- which are run by the opposition Scottish National Party (SNP) and the Labour Party respectively -- say it will erode their devolved powers and have described it as a "power grab".
"The EU (Withdrawal) Bill appears to represent a deliberate decision by the UK government to use the process of Brexit as cover for taking powers in areas of policy which are clearly within the responsibility of (the Scottish) parliament," said Russell.
The UK government denies this. It says that after the Brexit bill passes, there will be new discussions about which powers should be devolved and which should remain in London.
WHAT HAPPENS IF SCOTLAND AND WALES SAY NO?
For the UK parliament to seek consent and have it denied on such important legislation would mark a watershed in constitutional terms.
Britain's constitution is mostly unwritten and the devolution settlement is just 20 years old, with many of its fundamental features still evolving and being debated, so there is little clarity on where a constitutional crisis could lead.
The fear for those who want the bonds between the four nations to remain as strong as possible is that a constitutional clash could fuel the cause of Scottish independence. Scotland rejected independence in 2014 by a 10 percentage point margin, but the SNP, its dominant party, sees it as a long-term aim.
The fear on the part of the Scottish and Welsh governments is that it will leave them powerless to redress the economic and social impact of Brexit.
WHAT CAN SCOTLAND AND WALES DO TO INFLUENCE BREXIT?
Scottish First Minister Nicola Sturgeon and her Welsh counterpart Carwyn Jones have repeatedly insisted that the devolved administrations be given the opportunity to make meaningful contributions to the Brexit process.
Both have complained that British Prime Minister Theresa May has largely kept them in the dark and marginal to policy development. May has denied she is ignoring their voices.
Despite these frictions, the Scottish and Welsh governments are holding bilateral meetings with senior UK government officials to discuss specific aspects of Brexit.
They are also due to hold this year´s second joint ministerial committee meeting with the UK government in London in the autumn to discuss their policy needs.
(Reporting by Elisabeth O'Leary; Editing by Gareth Jones)