Brexit: Leaving may need consent of Scotland, Wales and Northern Ireland

The UK referendum vote was decisively won, but for Scotland and Northern Ireland it raises a multitude of questions. It may also be a legal struggle.

Exit first requires the repeal of the European Communities Act 1972 which allowed the UK to join the (then) European Economic Community.

The House of Lords report The Process of Withdrawing from the European Union quotes Sir David Edward, a former judge of the Court of Justice of the European Union.

In his view, Scottish Parliament consent would "be required" before the extinguishing of EU law since section 29 of the Scotland Act binds Scotland's Parliament to act in manner compatible with EU law. Further, given how the legislation is entrenched in Northern Ireland and Wales's devolution settlements, the Lords committee said it "has no reason" to believe that legislative consent is not needed from them, also.

If this is correct – and it will almost certainly be tested legally – the exit process is in trouble before it has started.

If the Leave campaign had considered the role of the devolved parliaments and assemblies, their thinking was based upon the blithe assumption that Westminster sovereignty carried all before it.

Second referendum

This may turn out to be the case but if there is conflict between national law and European law, the UK courts have to give priority to European law.

If European law is judged by those courts to be integral to the devolved institutions, things become awkward. Consent for an EU exit will certainly not be forthcoming from Scotland, let alone the other devolved institutions.

In the Scottish Parliament, only eight of the 129 members backed withdrawal. The Welsh National Assembly contains seven Ukip members and a sprinkling of anti-EU Conservatives, but the vast bulk of its 60 members oppose Brexit.

In Stormont, exit would be supported by about a third of its 129 members; the DUP, TUV, perhaps a few from the UUP (against leadership policy) and possibly People Before Profit. Scotland may choose an alternative strategy to a legal challenge by holding a second referendum on independence leading to a new membership application. It would surely be granted.

The Scottish National Party, with Green Party support, could get a referendum through Holyrood even if all the unionist parties were opposed. The UK government could refuse to accept its legitimacy. Such a reaction is probable. Or it could gamble on a second unionist triumph. A Westminster plea that a referendum is "non-binding" may fail to impress.

Northern Ireland opponents of EU withdrawal can use the Good Friday agreement to impede Brexit. The 1998 deal pledges close co-operation over its contents as “partners in the European Union”.

It pledges the North-South Ministerial Council to "consider the EU dimension of relevant matters, including implementation of EU policies". Its views must be "taken into account and represented appropriately at relevant EU meetings". Withdrawal means the UK cannot do this and would be in breach of international law if reneged. The Irish Government could legitimately take the matter to the UN.

Change of mind

Even if the Irish Government agreed to renegotiate the 1998 agreement – and why should it? – it might have to be put to the Irish electorate. If the Irish Government fails to act to uphold the agreement, it is inconceivable that political parties will not move. This might be abetter route for Sinn Féin than calls for a Border poll. That would not be granted by the Northern Ireland Secretary of State

Theresa Villiers

. And it would obviously be lost if confined to the North.

If all the above fail, perhaps the main hope for the many upset by the extraordinary events is there is nothing to stop the UK changing its mind. Jonathan Tonge is professor of politics at the University of Liverpool