Northern Ireland's politicians are expected to say no to Brexit by refusing to agree to the UK's withdrawal from the European Union. But Secretary of State Theresa Villiers has firmly rejected suggestions that either Stormont or Holyrood can veto the referendum result - insisting Westminster has the final say.
Scotland's First Minister Nicola Sturgeon has suggested that her parliament in Edinburgh could vote against a legislative consent motion to change the law there to reflect the result in the country.
MLAs here could be set to take the same course by blocking the motion to reflect the vote in Northern Ireland, where a majority (56%) opted for Remain.
All but one of the main Stormont parties - the DUP - campaigned against pulling out of the EU.
SDLP leader Colum Eastwood has claimed that the Assembly could vote down the Brexit motion.
But Leave advocate Mrs Villier made clear that Westminster held the ultimate authority in regard to enacting the UK's formal departure from the European Union.
"In the weeks and months ahead we will be working with both the Scottish Government and the Northern Ireland Executive on all these matters," she told BBC's Sunday Politics show.
"But ultimately it is parliament's decision whether we repeal the 1972 European Communities Act or whether we don't."
However, Mr Eastwood provided a different interpretation.
"We have been studying this for the last number of days - I don't think the Leave campaign have thought this through," he said.
"I don't think they expected to win and now they are in a situation where they don't know how to deliver this.
"We believe that the Northern Ireland Assembly and the Scottish parliament have the opportunity to say no."
He added: "We will not be about to give the Brexit campaigners the opportunity to ride roughshod over the democratic process in Northern Ireland."
Alliance Party deputy leader Naomi Long, who campaigned for Remain, said the devolved administrations could protest against Brexit, but she conceded Mrs Villiers' point that primacy rested in London.
She said Westminster could take back power from Holyrood and Stormont, therefore its authority was overriding.
"So let's not kid ourselves - if parliament sets its face to do this, whilst we can put up a strong argument against it, ultimately parliament remains in primacy," she added.
Ulster Unionist leader Mike Nesbitt, who supported Remain, called on First Minister Arlene Foster to make an urgent statement on Northern Ireland's future in the wake of the referendum result.
He said: "We have entered an era of uncertainty. The First Minister's first responsibility is to clarify that she will represent and reflect the will of the majority in Northern Ireland who voted to Remain, and not abuse her position by prioritising her party political stance.
"We have sought to bring an urgent oral question to the Assembly tomorrow."
The DUP's Sammy Wilson hit out at the "hysteria" following the referendum result.
The MP claimed: "Over the next weeks we can be sure that in their fit of bad-tempered pique, all the elements of the rejected Euro political, business and media elite will pour out their bile on the people of this country with a continuation of scare stories, threats and selective news coverage."
Sinn Fein warned it would not trust Mrs Villiers over negotiations on the withdrawal from the EU.
Finance Minister Mairtin O Muilleoir said he had never heard a Secretary of State "so out of touch" with the ordinary people on the ground.
Meanwhile, the Executive is set to meet imminently, perhaps as early as today, to discuss the fallout from Thursday's vote.
Mr Nesbitt said the Executive and Assembly needed to meet as soon as possible to "form an opinion" on the way forward.
Mr Eastwood insisted there was no need for a border poll - as demanded by Sinn Fein in the aftermath of the vote and firmly rejected by Mrs Villiers.
The Secretary of State said that, as a Brexit supporter, there was no difference in her continuing in office and Mrs Foster, a fellow Brexit supporter, staying on as First Minister.