There is a concern that infrastructure, such as cameras or border posts, could become a target and cause political instability. 29 Brexit could not only pose a threat to the peace process, but also be a source of instability for the border between Northern Ireland and the Republic. Thanks to EU membership (including the establishment of the single market in 1992) and the implementation of the peace process, the border between the two states has become a soft border. Since the abolition of customs controls, there have been virtually no physical manifestations of the border.65 This soft border was a symbol of successful peace-building and practical importance, as it guarantees free movement between the two states. This certainly explains why this theme was considered crucial by researchers. For example, the report published by the Northern Ireland Committee stressed that „regulation that maintains a soft land border … the absence of restrictions on travel within the UK should be a priority in the event of Brexit.” Indeed, Brexit could theoretically break down a hard border, because Northern Ireland, unlike the Republic of Ireland, would no longer be part of the EU. The border between Northern Ireland and the Republic would become an external border of the EU and should be managed to avoid the immigration of EU nationals to Britain. Therefore, border controls should be put in place. Some clauses will end parts of the Northern Ireland protocol, which was agreed last year, and pave the way for a return to a hard border.
In a February 2019 Sky Data poll, 79% of respondents voted in favour of a legal guarantee from the Irish government that there will be no hard border, even if it risks a Brexit without a deal on 29 March. In the same poll, 81% of respondents supported a reduction in economic relations with the UK if they were forced to choose and 19% supported a reduction in relations with the EU in favour of the UK in favour of maintaining open borders.  17 Prime Time Special – Ireland`s Call, RTE News, November 2015: www.rte.ie/news/primetime/2015/1104/739633-prime-time-cross-border-poll-test-page/ [August 6, 2016]. This means that, in order to meet EU requirements, certain controls will be required for certain products entering Northern Ireland from Great Britain (England, Scotland and Wales) and will create a regulatory and customs border in the Irish Sea. The Guardian reports that ” (British Prime Minister) Boris Johnson is preparing legislation that heralds the Brexit withdrawal agreement on Northern Ireland, a step that threatens the collapse of the crisis talks which the Prime Minister said were to be concluded within five weeks.” 34 Alasdair McDonnell, „McDonnell Brexit Address,” SDLP, 10 June 2016: www.sdlp.ie/news/2016/mcdonnell-brexit-address/ [5 August 2016].