A Bill to unilaterally amend the Northern Ireland Protocol will be introduced in Parliament on Monday amid controversy over whether the legislation will break international law.
The legislation will give ministers powers to override elements of the protocol, which was jointly agreed by the UK and European Union as part of the Brexit Withdrawal Agreement to keep the Irish land border free-flowing.
The arrangements instead require regulatory checks and customs declarations on goods moving between Great Britain and Northern Ireland.
Read more: Government to introduce controversial legislation to amend NI Protocol
The legislation will give ministers powers to override elements of the protocol, which was jointly agreed by the UK and EU as part of the Brexit Withdrawal Agreement to keep the Irish land border free-flowing.
The arrangements instead require regulatory checks and customs declarations on goods moving between Great Britain and Northern Ireland.
Unionists in Northern Ireland are vociferously opposed to the international treaty, claiming it has undermined the region's place within the United Kingdom.
The DUP has blocked the formation of a new power-sharing government at Stormont following last month's Assembly election in protest.
The Bill due to come before Parliament will see the Government move without the consent of the EU to change the terms of the protocol in a bid to reduce the checks on the movement of goods across the Irish Sea.
This could include allowing ministers to remove all customs processes for goods moving within the UK and enable the frictionless movement of agri-food goods staying within the UK.
It could also see businesses in Northern Ireland given the ability to choose whether to follow UK or EU regulations, depending on who they are trading with.
The EU has made clear that such steps would represent a breach of international law and could prompt retaliatory action from the bloc.
What is the NI Protocol?
The Protocol is an arrangement governing trade across the Irish Sea post-Brexit. It was negotiated between the UK and EU as part of the Withdrawal Agreement and how both sides overcame the main logjam in the Brexit divorce talks - the Irish land border.
To avoid disrupting cross-border trade and a return to border checkpoints, London and Brussels essentially agreed to move new regulatory and customs processes to the Irish Sea. That meant checks on trade between Great Britain and Northern Ireland, rather than on goods moving north and south within the island of Ireland.
Products shipped from Northern Ireland to Great Britain are largely unaffected by the protocol. The red tape instead applies on movement in the other direction.
Since the start of 2021, a range of regulatory animal and plant safety checks have been in operation, including physical inspections of a proportion of freight arriving at Northern Ireland ports. Customs declarations are also required for incoming commercial goods.
How does the NI Protocol work?
While the rest of the UK has left the EU, Northern Ireland has remained in the EU single market for goods and must also apply EU customs rules at its ports, even though it is still part of the UK customs territory.
The protocol also sees Northern Ireland follow certain EU rules on state aid and VAT on goods. Due to the extension of a "grace period" on a number of protocol provisions, some arrangements are not yet fully in force.
Why is the NI Protocol so controversial?
The post-Brexit checks on goods moving from Great Britain to Northern Ireland are fiercely opposed by unionists and loyalists in Northern Ireland, who argue that the creation of an "Irish Sea border" poses a threat to Northern Ireland's place in the UK.
The Protocol has been the subject of fierce criticism by unionists, prompting rallies and protests across the region in recent months. It has also been challenged in court.
Not everyone in Northern Ireland opposes the Protocol - businesses have taken issue with some of the fresh checks, but many also see a benefit in Northern Ireland having access to both UK and EU markets.
But Sinn Fein, the SDLP and Alliance say that while the Protocol is not perfect and can be tweaked, it is the best way to insulate Northern Ireland from the impact of Brexit.
How has it impacted on Northern Ireland politics?
Voters in Northern Ireland went to the polls on May 5, with Sinn Féin emerging as the largest party with 27 seats. The impasse and divisions of the Northern Ireland Protocol overshadowed the election campaign, with the DUP, led by Sir Jeffrey Donaldson, pledging not to enter the powersharing Executive until the issue of the protocol is solved.
The DUP had already pulled out of the Executive earlier this year ahead, citing opposition to the Protocol. The party lost a number of seats and saw its share of the vote fall.
The Alliance Party, which identifies as neither unionist nor nationalist, also had a very good election and surged to 17 seats - making in the third largest party in the Assembly. The result means that a majority of MLAs in the Assembly support retaining the protocol.
It was a historic result, with a nationalist party emerging with the most seats for the first time. Michelle O'Neill, the Sinn Fein leader in Northern Ireland, is in line to take the symbolic title of First Minister in the joint office of first and deputy first minister at the head of the Executive.
Sir Jeffrey, who would become deputy First Minister, has said that his party has a mandate not to enter the Executive until the UK Government addresses its concerns over the protocol, while also pointing out that every unionist elected to the Assembly opposes the protocol.
Parties in Northern Ireland have up to 24 weeks to nominate a First and deputy First Minister - if they fail to do so, Northern Ireland could remain without a Government until the end of the year.
What has the UK Government said?
The UK Government, alongside the EU, the Irish Government and the US administration, have urged the parties in Northern Ireland to form a powersharing Executive. In the days since the Northern Ireland election, the UK Government has made clear that it is willing to imminently take unilateral action that would scrap or override parts of the protocol.
What happens if the UK takes action on the NI Protocol?
Such a move would escalate the row between the UK and the EU, with warnings that it could result in a trade war.
Ireland's Foreign Affairs Minister has warned his British counterpart that introducing a Bill to unilaterally amend the Protocol will breach international law and "deeply damage" relationships.
Simon Coveney spoke by phone to Foreign Secretary Liz Truss at the request of the UK Foreign Office on Monday morning.
During the call, Ms Truss outlined her intention to publish legislation on Monday.
A spokesman for Mr Coveney said: "Far from fixing problems, this legislation will create a whole new set of uncertainties and damage relationships."
In Northern Ireland, the DUP has indicated that it would return to powersharing if the Protocol is resolved.
But DUP MP Sammy Wilson has said his party needs to see the final form of the Government's legislation before deciding whether to support it.
Mr Wilson told the BBC's Good Morning Ulster programme on Monday: "We are at the first stage; we are pleased that the Government at least is recognising there is an issue, that they are bringing forward legislation in the face of the EU's intransigence to deal with the problems."
Prime Minister Boris Johnson has insisted that resolving the Northern Ireland Protocol problems is "relatively simple".
Mr Johnson told LBC Radio he disagreed with claims that the move breaks international law, arguing that "our higher and prior legal commitment as a country is the Belfast/Good Friday Agreement and to the balance and stability of that agreement".
He also warned that a trade war over changes to the Protocol would be a "gross overreaction" by Brussels.
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