THE crucial hearing in the UK Supreme Court on whether the Scottish Parliament will keep devolved powers after Brexit begins tomorrow, and the core of the Scottish Government’s case has already been put in writing by Lord Advocate James Wolffe QC.

In his 75-page written submission to the two-day hearing by seven judges, the Lord Advocate states that the UK Government law officers are “wrong as a matter of domestic constitutional law” that Brexit will “return to the sovereign (UK) Parliament the areas of competence which had been, under the treaties, assigned to the province of the EU institutions”.

The case has been brought by Theresa May’s Government following the Scottish Parliament’s passing of the Continuity Bill which aims to preserve devolved powers after Brexit. If the Scottish Government loses, Westminster will be able to impose laws even on currently devolved matters – what the First Minister Nicola Sturgeon has called a power grab”.

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The UK Government case centres on four questions. The chief of which is “whether the Scottish Bill as a whole is outside the legislative competence of the Scottish Parliament”.

Wolffe’s submission states that the Court should answer all the question “in the negative” because the Continuity Bill does not relate to reserved matters, nor is it incompatible with EU law. The core of the Scottish Government’s case is stated as: “The underlying principle of devolution reflected in the Scotland Act 1998 is that everything which is not explicitly reserved to the UK Parliament is a matter for the devolved institutions.

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“In relation to such matters – subject to the other limits on the legislative competence of the Parliament – questions of executive policy are exclusively for the Scottish Government, and questions of legislative policy are primarily for the Scottish Parliament. Consistent with that principle, the Scottish Bill makes provision, in a way which does not relate to any reserved matter, for the domestic law consequences of withdrawal from the EU.”

Wolffe wants the case thrown out right at the start. While accepting questions on the “legislative competence of the Scottish Parliament”, he argues that “neither the Scottish Bill, nor any of its provisions, is susceptible to review on common law grounds.”

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The Lord Advocate says the UK Government law officers “are also in error” with their objection that the effect of the Scottish Bill “… to purport to confer on the Scottish institutions the power to determine, as a matter of legislative policy, what the substantive content of EU-derived Scots law should be after withdrawal.”

Wolffe states: “Except insofar as matters are reserved to the UK Parliament, it will be the responsibility of the Scottish institutions to determine, as a matter of legislative policy, what the substantive content of EU-derived Scots law should be after withdrawal.

He adds: “EU law is not a reserved matter; and will not become a reserved matter by reason of the UK’s withdrawal from the EU. If the UK Parliament wishes to make EU law a reserved matter, then it must do so expressly.”

Later in his submission Wolffe argues: “Further domestic measures may well be required at some future time, to implement a future treaty on the future relationship between the UK and the EU. The Scottish Bill does not pre-empt any future treaty arrangements; nor could it. Nor does it preclude future measures to give effect in domestic law to any obligations undertaken in such a treaty.”

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In what is effectively a rebuke to the UK Government ministers, Wolffe adds: “In light of the passage by the Scottish Parliament of the Scottish Bill, and the refusal of consent by the Scottish Parliament to the UK Bill, it would have been open to the UK Government to bring forward amendments to the UK Bill to make express provision for the interface between the two pieces of legislation ... the UK Parliament has power to amend, or indeed repeal, the Scottish Bill. The UK Government chose not to seek to address the issue by express provision.

“Any uncertainty, confusion or ambiguity arising from the presence on the statute book of these two Bills will be a consequence of that legislative choice.”

Neither the Scottish Government or UK Government are adding to their original statements in advance of the hearing.