If the UK and the EU-27 do not agree on a free trade agreement by the end of the transition period, Britain will find itself in a “no deal” situation, but with the possibility that Northern Ireland will remain under the Northern Irish backstop (and agree to stay). While a “no deal” would have a huge impact on Britain, the possibility of Northern Ireland remaining in the backstop would lead to an extremely complex outcome in trade between Britain and Northern Ireland. In July 2019, Theresa May resigned and Boris Johnson became prime minister, with Boris Johnson saying he wanted to replace the Irish backstop as part of the withdrawal agreement.  On August 19, in a letter to the President of the European Council, the Prime Minister described the agreement as “undemocratic and incompatible with the sovereignty of the United Kingdom.”  He stressed that it was “incompatible with the final objective desired by the United Kingdom” for its relations with the EU. Its third reason why the backstop is not enforceable is that it could “weaken” the Good Friday Agreement and the peace process in Northern Ireland. Tusk replied that those who opposed the arrangement without “realistic alternatives” supported the re-establishment of a hard border on the island of Ireland. That`s the reality, “even if they don`t admit it,” he added. “The backstop is an insurance policy to avoid a hard border on the island of Ireland unless an alternative is found,” Tusk tweeted.  Irish government sources have held that “the real purpose of the backstop is to maintain the status quo by guaranteeing freedom of movement and not a hard border on the island of Ireland; which is of paramount importance to the GFA.
The reality is that Brexit itself poses a threat to the GFA.  Paul Bew, a crossbench counterpart, noted that the top-down nature of the backstop reverses the ascendant character of the Good Friday Agreement, risking that “the current deterioration in North-South relations could intensify in unpredictable and dangerous ways.”  The Irish backstop (formerly the Northern Ireland Protocol) is a non-existent annex to a draft Brexit withdrawal agreement drawn up by the May government and the European Commission in December 2017 and finalised in November 2018, aimed at preventing an obvious border (with customs controls) between the Republic of Ireland and Northern Ireland after Brexit. On 14 November 2018, after a five-hour meeting, Prime Minister May announced that her cabinet had approved the draft withdrawal agreement with the EU.     On the same day, the government issued a statement on the agreement on the withdrawal of the United Kingdom of Great Britain and Northern Ireland from the European Union, stating that negotiations on the future relationship between the United Kingdom and the EU had not yet been concluded and that the (binding) withdrawal agreement would not be concluded without an agreed (non-binding) political declaration on the future relationship. On the basis of the fact that nothing has been agreed until everything has been agreed.”  Despite this, the EU and the UK are determined to conclude a future trade agreement and the transition period can be extended for up to two more years (if extended by two years, it would end in December 2022). .