Irish Sea border

The Irish Sea border is an informal term for the trade border between Northern Ireland and Great Britain. It was specified by the Ireland/Northern Ireland Protocol of the Brexit withdrawal agreement (February 2020), was refined by the Joint Committee in December 2020,^[1] and came into effect on 1 January 2021 following the end of the Brexit transition period. As a result of the Agreement, Northern Ireland remains aligned to the European Single Market in a limited way for goods,^[2] whilst remaining part of the United Kingdom customs territory and the UK internal market. Its effect is that the need for customs checks on the Irish border has been avoided, and a hard border has not been re-established.^[3]

This Irish Sea border was the option taken by Prime Minister Johnson in October 2019 to break the impasse of the "Brexit Trilemma" (of three competing objectives: no hard border on the island; no Irish Sea border; and no British participation in the European Single Market and the European Union Customs Union: it is not possible to have all three.^[4])

Under the terms of Article 18 of the protocol, the Northern Ireland Assembly has the power (after 31 December 2024) to decide whether to terminate or continue the protocol arrangements. "The Withdrawal Agreement doesn’t state how Northern Ireland should give consent [to continue] – it is for the UK to determine how that decision is made" but the UK Government has already declared that the decision will be made by a simple majority of Assembly members.^[5] In the event that consent is not given, the arrangements would cease to apply two years thereafter. The Joint Committee would make alternative proposals to the UK and EU to avoid a hard border on the island of Ireland. If consent is given, then the question may be put again after a further four years.^[5]

At the 2022 Northern Ireland Assembly election, parties favouring continuance of the protocol won 53 of the 90 seats.^[6]