After twenty-five years of bloody conflict, the Good Friday Agreement of 1998 established a durable peace in Northern Ireland. There are now generations who have lived there free of the terror and violence endemic during that time.

Yet, as the state marks the centenary of its foundation, serious problems remain unresolved, including sectarianism, dealing with the legacy of the past, and mediocre economic performance. This past April, tensions over the fallout from Brexit spilled over into week-long violent protests.

The 1998 Agreement brought the decades-long conflict to an end by establishing a power-sharing government that ensured the representation of both communities: one unionist, predominantly Protestant and primarily identifying as British; the other nationalist, predominantly Catholic and primarily identifying as Irish. The devolved government—known as the Executive—is led jointly by representatives of the two biggest parties, the Democratic Unionist Party (DUP) and Sinn Féin. It also provided that while Northern Ireland remains part of the United Kingdom (UK), a united Ireland would be established by a majority vote in a referendum.

The exit of the UK from the European Union (EU) is the most significant change to the complex political, social, and economic landscape of Northern Ireland since the Agreement came into place. The shared EU membership of the UK and Ireland was an important dimension of the peace process and offered a benign context for the Good Friday Agreement. A sense of a common European identity softened the binary division between the two communities, which in turn allowed for a shared identity of Northern Irish to begin to emerge, especially among younger people. Brexit, which was supported by the DUP but rejected by a majority of Northern Irish voters, has reignited tensions and fueled a divisive but unavoidable debate on the future of Northern Ireland. It is the feeling among many voters that they have been taken out of the EU against their will that has restarted the debate on Irish unity.

From the start, the Irish Government and some leading British figures saw that Brexit would destabilize Northern Ireland. The key issue was this: the land frontier between Northern Ireland and the Republic, which twists and turns for over 499km, would become an EU-UK border. This would require controls between North and South, a so-called hard border, reversing much of the recent progress and potentially threatening peace. Ireland persuaded the rest of the EU that this outcome had to be avoided, and avoiding the need for one became a key part of the EU approach to the Brexit negotiations.

The UK agreed with the EU that a hard border must be avoided, while preserving the integrity of the EU Single Market. However, it emerged that there were only three ways to do this, none easy: customs barriers between the island of Ireland and the rest of the EU, which was unthinkable for Ireland; the UK effectively remaining in the customs union and some of the single market, which was agreed to by Prime Minister Theresa May in late 2018, but strongly rejected by the UK Parliament and by many in her own Conservative Party; and the installation of some physical checks and controls on the movement of food, animals, and goods between Great Britain and Northern Ireland at Northern Ireland ports. This so-called Irish Sea border was anathema to unionists and many British members of Parliament. The stalemate was eventually broken in late 2019, when to avoid a no-deal Brexit the new British Prime Minister, Boris Johnson, effectively accepted such a sea border. The unionist sense of betrayal was strong, as Johnson had resolutely said he would never do this. He has exacerbated matters since by denying the full consequences of what he had agreed.

The rules were set out in a Protocol and took effect at the start of this year. The Protocol allows unfettered access to the British market for Northern Irish exporters. However, the controls operating between Great Britain and Northern Ireland are impacting both consumers and businesses. Some of the disruptions are likely to be growing pains and will be resolved in full or in part, but some negative consequences will inevitably persist.

While concrete problems are challenging, constitutional and political issues can be incendiary. Unionists argue that the differentiation of Northern Ireland from Great Britain is a breach of its constitutional status as guaranteed under the Good Friday Agreement. This is not so but the psychological and political effects are real and understandable. They are made worse by renewed high-profile debate about a possible referendum on a united Ireland, opposition to which is existential for unionists. Unionist anxieties are heightened by demographic and societal change which may soon mean that they no longer constitute a majority in Northern Ireland.

Unionists are now demanding that the Protocol be dismantled. Anger spilled over into rioting in April, the worst violence Northern Ireland has seen in years, and the mood remains tense. The controversy contributed to the recent removal of the DUP leader and First Minister, Arlene Foster, after a party revolt. Her successor, Edwin Poots, has maintained a hard line on overturning the Protocol. This is not a serious option, as it would re-open the whole Brexit deal. But the mood in much of unionism remains confrontational, with some prepared to threaten the continuation of the Executive and co-operation with the Irish Government.

However, while working with the EU on its practical implementation, the rhetoric of the UK government is also becoming increasingly aggressive in demanding more fundamental change. The EU is conscious of its own interests and can be distrustful of British good faith on this and, more generally, while open to improvements to the working of the Protocol, is not prepared to move beyond its legal parameters.

Some checks and controls are an inevitable consequence of Brexit, and their location between Great Britain and Northern Ireland was agreed upon by both sides in the Protocol. But the current political and economic instability can and should be mitigated.

The path forward is to push for the most pragmatic and flexible application of the Protocol possible. EU and UK negotiators have been making progress in trying to solve some of the practical problems. However, the potential for change is currently limited both by the need for the EU’s customs and single market rules to be applied and by the current strains in the EU-UK relationship, arising from the EU perception that the UK is not fully committed to implementing the terms of its Brexit deal.

Eventually, more creative approaches to the management of the sea border may be conceivable, given the unique political and geographical position of Northern Ireland. Some more moderate political and business leaders have also pointed out that by in a sense remaining within both the EU and UK markets, there is some potential for Northern Ireland to have the best of both worlds in terms of trade and investment, a concept that fully adheres to the spirit of the 1998 Agreement.

But if in the short-to-medium term the lid is to be kept on the situation, and the institutions of the Good Friday Agreement are to function, some demonstrable progress will need to be made for unionist leaders to point to, while finding a way to back off unrealistic demands that the Protocol be scrapped. This will require maturity and flexibility not just in Belfast but in London, Brussels, and Dublin, with each recalling its responsibility to protect the peace process and the gains that have been made for the people of Northern Ireland. However, the demons which have emerged from Pandora’s box will not be easily forced back into it.

Rory Montgomery was the Irish Permanent Representative to the European Union from 2009-2013, and from 2014-2019 had responsibility for Brexit policy at the Department of the Taoiseach (Prime Minister) and then the Department of Foreign Affairs. He is now an honorary professor at Queen’s University, Belfast, and a visiting fellow at Trinity College, Dublin, and writes on Northern Ireland and EU issues.