As far as Brexit is concerned, a „hard border“ means a limited number of authorized (and physically controlled) crossing points, occupied by customs officers and police and supported by military personnel in times of tension.  Drivers of vehicles crossing the vehicle must report goods during transport, commercial carriers must submit bill of lading and prove that the goods meet the minimum standards of the area concerned. Tariffs (in the form of tariffs) may be due.  This was the position at the border between 1923 and the Single European Act of 1993.  (In this context, a „hard border“ does not mean a fortified border, but during the unrest British security forces blocked many unauthorized crossing points for security reasons. In accordance with the provisions of the Common Travel Area, British and Irish citizens are free to cross the border without passport control. Under the withdrawal agreement, Northern Ireland has a different customs and regulatory regime than the rest of the UK, unless a free trade agreement removes disputes. This condition is due to the need to avoid the re-establishment of a hard land border that would sabotage the Good Friday agreement. Given that Johnson`s preferred Brexit model takes Britain out of the internal market and customs union, the legal requirement for a border in the Irish Sea comes into force.
This is something that the UNITED Kingdom has decided for itself. The Irish government supported this proposal.  It was strongly rejected by the Democratic Unionist Party as a weakening of Northern Ireland`s place in the UK and is seen as the main reason why Theresa May`s withdrawal agreement was never approved by the British Parliament.  The British government had rejected the original proposal. When Boris Johnson replaced May last July as prime minister, he pledged to review the Brexit deal. Last week, he agreed with EU heads of state and government to withdraw the backstop and replace it with a revised protocol for Northern Ireland4, which will come into force at the end of the transition period (currently scheduled for 31 December 2020). Northern Ireland will remain on UK customs territory and VAT territory, but will be in line with EU rules in these areas. It will also remain largely in line with EU product rules. Four years after the end of the transition, the Northern Ireland Assembly will vote on the continuation of these agreements.5 With the exception of the approval mechanism, the protocol is similar to the one originally proposed by the EU and rejected by Theresa May only in Northern Ireland. Some congressional leaders have pointed to the cost of a no-deal Brexit for Northern Ireland.
House of Representatives spokeswoman Nancy Pelosi sounded the alarm last April as she and several colleagues travelled to London, Dublin and Belfast to warn that Congress would not support an American United Kingdom. 30 The co-chairs of the House`s Friends of Ireland caucus, MPs Richard Neal and Peter King, made a similar bipartisan promise.31 The congressional debate took on more partisan nuance in the letter from Senator Tom Cotton and 43 Republican colleagues to Prime Minister Johnson, who defended a trade deal „regardless of the Situation of Brexit.“ 32 The aim of this document is to show that in order to find a solution to the Irish border issue arising from Brexit, we must go beyond the simple economic, social and economic threats posed by Brexit in Northern Ireland and in the cross-border relations between Ireland and Northern Ireland. The current problem of the Irish border is fundamentally political and constitutional and not socio-economic. But as a political and constitutional issue, the persistent problem of the Irish border is not just a consequence of Brexit. It is above all the result of the unfinished Belfast/Good Friday Agreement (GFA).