Would it really be so terrible if there were checks at the Irish Sea instead of at the border between Northern Ireland and Ireland? Such checks could be carried out without threatening the constitutional status of Northern Ireland as part of the UK.
Some say that there should be no differences between Northern Ireland and the rest of the UK but there are already differences of the most fundamental kind. The Belfast Agreement accepts that if the majority of people in Northern Ireland vote to join the republic then the UK government will not stand in their way. There is also a British-Irish Council which gives the Irish Government a role in policy making north of the border.
Northern Ireland already has special status and it is only because we in the UK have given it a unique position that additional checks at the border are necessary. When we leave the EU, the relaxed border will no longer mark the division between two EU members but between the EU and a third country.
Michel Barnier explained his fears in the clearest terms to the House of Lords Select Committee on the European Union on Tuesday 17 July 2018.

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