(First, let me say here that I am an American, and therefore not fully versed on IRA / British conflict, definitely not enough to give an educated definition. On this issue, I look at the problems from a detached and decidedly American viewpoint.)
Question
Northern Ireland went through “the troubles” for over 30 years, until a peace deal was signed in 1998. “The troubles” is a regional name for the terrorist / civil war attacks by some militant Irish nationals against the English. Geographically and economically the Irish and English are intertwined and finally settled into stable political relationship. And yet, we hear rumblings of problems in the international relationship between Ireland and Great Britain as well as threats from the European Union. What is threatening the equilibrium now?
Background
Republic of Ireland is now a nation occupying about 3/4’s of the island of Ireland just west of England. And that rule was maintained for hundreds of years because it was economically beneficial for Great Britain.
Historically, the land was conquered and then ruled by the British. British rule from about 1701 included multiple systems designed to disadvantage Roman Catholics and Protestant Dissenters (i.e. protestants that were no part of the Anglican Church). The Irish rural economy was devastated by British ownership of the land and a two-year cycle of horrible weather that is known as the “Great Frost”. Irish antagonism towards Great Britain grew mightily during this time because what food was grown was sent to British’s landowners while the population in Ireland suffered.
In 1801 Great Britain brought Ireland into the United Kingdom as part of the United Kingdom of Great Britain and Ireland, partially to reduce violent protests for independence. It did not work. And relations deteriorated further when “Great Famine” or the “Irish Potato Famine” from 1845 – 1851 occurred. The famine renewed support for the fight for independence as profits for British landholders were valued more than the Irish people.
During the famine approximately one million people died from hunger and at least 1 million more emigrated, mostly to the United States and Canada. This established a large population of Irish in both countries. And the Catholic Irish thrived in both countries. This diaspora supported the drive for an independent Ireland both emotionally and financially.
The independence movement fought British forces, prevailing in 1919 – 1921. This was during World War II, with the British forces occupied on the continent. In 1921 the peace treaty between Great Britain and Ireland provided an opt out of the new nation for Northern Ireland, which was promptly used. Northern Ireland has stayed part of the United Kingdom since. The treaty itself planted the seed that led to the Roman Catholic Free Irish continuing the fight. Some Irish independence figures continued the fight, now against the Northern Irish region populated by a mix of Anglican and Catholic populations.
The Irish people that fought for independence continued a war against the British in Northern Ireland and terrorist attacks in London. That did not end until the peace deal in 1998, the “Good Friday Agreements”. This agreement has brought a sense of normalcy to the relations between the countries.
By 1998 both Ireland and Great Britain were in the European Union and the importance of the border between Ireland and Northern Ireland was greatly reduced. People and goods traveled freely between the various states in the EU. Movement of people and goods trade increased between the state of Ireland and the region of Northern Ireland. The impediments raised by geography and competing economics was greatly mitigated by mutual inclusion the the EU.
Brexit
Fast forward to Brexit, which saw Great Britain leave the European Union. One of the biggest issues during the Brexit negotiations was resolving the status between the Republic of Ireland and Northern Ireland – still part of the United Kingdom. Neither side (the Irish nor the British) wanted to return to the toxic and antagonistic situation that led to violence before EU membership for both countries. And so a compromise was agreed to during exit negotiations with the European Union. Northern Ireland was to stay within the European Unions Trading area, so as to prevent a hard border on the island itself. Introducing a customs and travel border on the Irish border was considered provocative and crippling to the economy of Northern Ireland.
Of course, this agreement was fraught from the start. The agreement meant that goods, primarily food stuffs, had to be inspected before delivery into Northern Ireland. The negative economic impacts were not limited to Northern Ireland – British internal trade. The agreement essentially put an international border within the singular country of the United Kingdom of Great Britain and Northern Ireland. Since Brexit, the British Government has tried to overturn or ignore this agreement. The European Union and Ireland have been steadfast in insisting on the agreement was signed as part of International Law.
The result is that most things traveling from Northern Ireland to Great Britain move freely. But goods traveling into Northern Ireland, even from Great Britain, must go through European Union’s inspection. This has kept the border between Ireland and Northern Ireland open but means that effectively Northern Ireland is still a part of the EU mechanisms, if not part of the European Union.
It is a compromise that cannot last indefinitely. It would be like having Hawaii as part of the "Comprehensive and Progressive Agreement for Trans-Pacific Partnership" with Japan although it still would be technically part of the United States. Companies on either side of the Irish Sea now face delays and different legal systems. Leaders in Northern Ireland and the British Parliament worry that this will lead to a Northern Ireland joining the Republic of Ireland, or a de facto situation where Northern Ireland drifts closer to the EU and farther from Great Britain.
Current Situation
Great Britain, under Boris Johnson, threatened to ignore the treaty. This position continues to be held by the current government. But introducing a hard border on the island might lead to a restart of the violence of the 1970s / 80s. The EU is willing to do some renegotiation on the treaty, but talks broke down repeatedly. Talks between the parties finally restarted in October 2022 but finding a good resolution will be extremely difficult.
And if that difficulty is not overcome, the situation has no good solution.