The international peace and security problems traditionally occupy a central position in the modern IR agenda. Current international system is still characterized by the presence of hundreds unsolved armed conflicts which have a direct influence on the international security. Another challenge is the so-called frozen international conflicts with potential to fire up again. One of the notable examples of this kind of conflicts is the situation in Northern Ireland. The conflict between Great Britain and Ireland finished with the creation of Republic of Ireland and Northern Ireland which remained in the UK. Formally conflict was solved in 1998 with signing of the Belfast Treaty. But de-facto the Good Friday Agreement was only a starting point in the peaceful resolution, forming the basis for further progress. Still the situation in Northern Ireland is far from being stable and the conflict in cannot be counted as finished. The absence of war does not provide full and accepted by all peace, as the rivalry is going on. The street upheavals and riots continue, the discontent of the population is growing. Political and social landscape of Northern Ireland is being changed and this influence the implantation of Belfast Treaty. Another important factor which influence the peace process in Northern Ireland is Brexit. The majority of population of Northern Ireland is strongly against Brexit. Besides any other political consequences of Brexit, the restoration of hard border between Northern Ireland and Ireland might profoundly worse the situation and provoke the conflict escalation.