The answer begins in 1921, when 26 of Ireland’s 32 counties gained independence from the United Kingdom.
Since then, the UK and the Republic of Ireland have pursued a degree of regulatory alignment to facilitate reasonably easy movement and commerce between the Republic and the six counties that make up Northern Ireland. Although political pressures have often meant that this easy movement has been theoretical rather than actual, there has always been a degree of regulatory alignment across the island of Ireland and between Ireland and the UK as a result.
In the 1950s, after the UK changed its immigration laws to restrict the rights of Commonwealth citizens to come to Britain, the Irish government followed suit to maintain the Common Travel Area (the free movement agreement comprising the UK, the Republic of Ireland, the Isle of Man and the Channel Islands, in which citizens of all four places can move and live freely in all four territories without restriction). The UK’s unwillingness to join the Schengen Area, which facilitates passport-free travel within 26 European countries, means that the Republic of Ireland remains outside it as well. And both countries joined the European Economic Community (EEC) at the same time, again for this reason.
So this is about the EU?
The shared regulatory framework of EEC membership, particularly after the creation of the single market, the customs union and the modern European Union across the late 1980s and early 1990s, meant that these arrangements largely ceased to be a bilateral matter between Ireland and the UK, and became a Europe-wide one: integration across member states facilitated the pre-existing alignment and integration between the island of Ireland and Great Britain. (The so-called east/west border.)
That regulatory alignment helped facilitate the political agreements reached in 1998 (the Good Friday Agreement) and across the rest of the decade, which largely ended the period of prolonged and extensive political violence in Northern Ireland and across the UK.
How did Brexit change things?
After the UK voted to leave the EU in 2016, the future of that regulatory alignment was thrown up in the air. Ireland remains in the EU and is highly likely to do so for the foreseeable future, but the UK is out of the EU and it is equally unlikely to be able to rejoin for the foreseeable future.
Both the law of the EU and that of the UK are ever-changing, which meant that the Brexit talks had to enshrine some kind of legal framework to keep Ireland and Northern Ireland’s regulatory frameworks aligned with each other.
What was Theresa May’s “backstop” solution?
Theresa May’s preferred approach was an “all-UK” one – the so-called backstop – which would have meant that the whole of the UK continued to have the same regulatory framework as the EU as far as goods (that’s tangible items sold to people, such as cars, computers and contraceptives) and phytosanitary standards (that’s the type of regulations that determine how to transport and treat plant, animal and human life – essentially: food, live animals and medicines).
The problem with May’s backstop, however, was that the EU disliked it because it took a big chunk out of the single market, and Conservative backbenchers disliked it because it involved a high level of rule-taking for the UK after Brexit. It was rejected by the UK parliament and there is no prospect of it being brought back: Conservative MPs are not going to ask for it and the EU is not going to offer it again.
What was Boris Johnson’s “Northern Ireland protocol” solution?
Boris Johnson opted to go via a different route: the Northern Ireland protocol, which keeps only Northern Ireland aligned on goods, phytosanitary standards and a handful of other areas.
Why did he do this? Well, there is a policy argument to be made that a regulatory “east/west” border already exists between Northern Ireland and Great Britain as far as agriculture and energy are concerned, so a little thickening of it is not a significant change. But there was also a political imperative. Johnson did not want to go to the country in the 2019 election as the candidate of a no-deal Brexit, and so he reached for the only other alternative: for Northern Ireland to remain within the regulatory orbit of the EU and Great Britain to leave.
What’s happening now?
In the present day, the protocol is creating political strain in Northern Ireland. People who want Northern Ireland to remain in the UK feel, not unreasonably, that the protocol incentivises closer economic links with Ireland and discourages them with Great Britain, putting a strain on the union between Northern Ireland and Great Britain. Doctrinaire Brexiteers, meanwhile, dislike that the protocol makes the European Court of Justice the ultimate referee of any breaches of it.
Can this be resolved?
The UK and the EU are currently in talks to tweak the arrangement. But whatever changes are made, the problem remains: that since 1921, relations between Ireland and Northern Ireland have involved a high degree of regulatory alignment. During the period of the United Kingdom’s membership of the EU, that was facilitated by a common set of European standards. Before the two states joined the European Union, the UK – the larger state – essentially set the terms of alignment.
Brexit means that it is now Ireland that is part of the larger bloc, and British politics has yet to adjust to that changed relationship.