The Northern Ireland Protocol has been at the heart of UK politics for the past couple of years.
Since the Brexit transition period ended on 31 December 2020 the protocol has been a point of friction between Westminster, Belfast and the EU.
Now, nationalist party Sinn Fein has make history by becoming the first nationalist party to win the most seats in Northern Ireland Assembly elections, with the unionist DUP experiencing big losses.
The protocol is being blamed for much of that turnaround in votes, with the DUP threatening to not take part in government unless the protocol is abandoned or replaced.
What is the Northern Ireland Protocol?
The UK and EU agreed to put the protocol in place after Brexit to avoid the introduction of a hard border between Ireland and Northern Ireland.
Lorries can continue to cross the border from Northern Ireland into the Republic without having paperwork and goods checked – as they did when the UK was in the EU.
Because Ireland remains in the EU, a new arrangement was needed to reflect the EU’s strict food rules and border checks.
The protocol states that Northern Ireland will remain part of the UK’s customs territory – so if the UK signs a free-trade deal with another country, Northern Irish goods would be included.
However, Northern Ireland has to stick to some EU rules to allow goods to move freely into the Republic and the rest of the EU.
Goods moving from Great Britain to Northern Ireland are not subject to a tariff unless they are “at risk” of being moved into the EU afterwards.
How does it work in practice?
Products from Great Britain entering Northern Ireland have had to undergo EU import procedures at the ports.
To carry out those checks, an Irish Sea border has effectively been imposed – which Boris Johnson promised would not happen.
This has resulted in delays and sometimes sparse supermarket shelves as some suppliers have decided to stop selling to Northern Ireland due to the new cost and difficulty.
There have also been problems with “medicines, on pets, on movements of live animals, on seeds, on plants and on many others”, former Brexit negotiator Lord Frost said last year.
Not all checks specified by the EU have been fully implemented, such as paperwork for supermarkets which was reduced during a temporary “grace period”.
However, those grace periods have been extended by the UK, which has resulted in a row with the EU as it says it is a breach of international law.
What do the unionists think of the protocol?
All three unionist parties – the DUP, Ulster Unionist Party and Traditional Unionist Voice – are very much opposed as they argue the Irish Sea border threatens Northern Ireland’s place in the United Kingdom.
The DUP’s Paul Givan resigned as first minister over the matter in February.
DUP leader Sir Jeffrey Donaldson said before the elections his party would not re-enter the Stormont Executive – which requires both nationalists and unionists to function – until Westminster acts to “protect Northern Ireland within the United Kingdom”.
The party said it will only enter into a power sharing government if other parties agree the protocol must be removed or replaced.
He has claimed the protocol has led to higher prices than in the rest of the UK, particularly for dairy products and chilled convenience foods.
What do nationalists think of the protocol?
The two main nationalist parties, Sinn Fein and the SDLP, back the protocol.
Sinn Fein is in favour of the protocol as it prevents a hard border on the island of Ireland, and they want the island to be one nation.
Its vice-president Michelle O’Neill, who is set to become first minister after the party’s election victory, said it is also a “mitigation against Brexit”.
With Sinn Fein becoming the largest party in Stormont, nationalist views are likely to be bolstered on either side of the Irish border which could mean further resistance to changes to the protocol.
Can Northern Irish parties do anything about the protocol?
The Assembly can vote on whether to continue with the protocol in 2024, but would require cross-community support to extend the deal by eight years.
With the unionists very much opposed, this seems unlikely at the moment.
However, a simple majority vote in favour could extend the arrangement for a minimum of four years.
What is Article 16?
Article 16 is a clause intended to be used when the protocol is leading to serious “economic, societal or environmental difficulties that are liable to persist, or to diversion of trade”.
It allows either the UK or the EU to act unilaterally to suspend parts of the Brexit treaty to avoid such difficulties.
Invoking the article is considered a last resort when the parties have been unable to agree a joint approach to solving the problems.
Foreign Secretary Liz Truss said in January that if a negotiated solution could not be reached she is willing to trigger Article 16, which Brussels said would “lead to instability and unpredictability”.
This could prompt the EU to respond with retaliatory measures such as imposing import taxes on some areas of trade.