Consider the following sequence of events:

  1. In March, the UK fails to reach an agreement with the EU and exits with no deal.
  2. The UK leaves the British side of the Irish border open, to comply with the Good Friday Agreement (and to comply with the UK's repeated and strenuous assurances that there would be no hard border). No customs personnel are placed there, there are no immigration checks, etc.
  3. Ireland begins the process of placing customs and immigration along the Irish side of the border, to comply with EU customs laws.
  4. The UK accuses Ireland of violating Good Friday, and demands that Ireland keep the border open.
  5. Ireland is thus forced to either violate Good Friday or leave the EU customs union.

Does anything specifically prevent the UK from doing this? If not, why is Theresa May not using the threat of this outcome as leverage against the EU? Based on the failure of the Chequers deal, it's obvious she is in dire need of some kind of leverage. Of course, such a threat need not be explicit; she could just as easily say something like this in a public statement:

Although [the latest round of negotiation] was discouraging, the people of Ireland and Northern Ireland need not worry. The UK is fully committed to an open border, even in the unlikely event we do not agree on a deal with the EUC. We trust that Ireland shares our commitment.

(Later, when journalists start asking questions about the boldfaced sentence, state that it is not UK policy to comment on future actions of other countries and that the journalists must consult Ireland.)

Presumably, the UK would eventually want to negotiate a trade deal with someone other than the EU, and an open border with the EU would make that difficult or impossible, but that's not nearly as immediate a problem as (5). The question is whether the UK has already made some agreement that prevents this state of affairs, not whether the UK might have a hypothetical future reason to do so.

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    Comments deleted. Please don't use comments to answer the question. Write a real answer instead.
    – Philipp
    Commented Sep 23, 2018 at 18:24
  • This sort of possibility has occurred to me, especially on those occasions when Brexiters have said something like "We would have no intention of establishing a border in Ireland. It would be a matter for the EU to decide if they were to establish one". It is, of course, an entirely disingenuous rationale. If there were tariffs in both directions (the inevitable consequence of a "no deal") then it would be as much in Britain's interest to prevent goods entering Northern Ireland without the duty being paid, as it would be for the EU to prevent British goods entering the Republic.
    – WS2
    Commented Sep 24, 2018 at 8:00
  • I'm afraid the problem is even more complex. For both UK and EU to respect WTO rules there would need to be some kind of border enforcement and the "most favored nation" principle (see, for example, this fact-check). There have been indeed some threats running around but it's mostly for popular consumption. They do not reflect the real difficulty of the problem and it would likely be interpreted by the EU as an empty threat. Further it could potentially be damaging politically for May.
    – armatita
    Commented Sep 24, 2018 at 8:24
  • The UK took Ireland once...
    – SCFi
    Commented Sep 24, 2018 at 11:58
  • The UK has already begun its post-Brexit WTO negotiation of schedules, so what you allude to in the last paragraph is already happening. And regarding your #5: it's not that dichotoumous see politics.stackexchange.com/questions/32340/… Commented Sep 24, 2018 at 17:18

5 Answers 5


This argument is pure sophism. No-one would think that breaking the Good Friday Agreement by the EU establishing a hard border was entirely the EU's fault. They would blame the UK for failing to find a solution, and for backing out of the backstop solution that it has already signed a legally binding commitment to.

It would also bring down the UK government as it is reliant on the DUP for a working majority in parliament, and the DUP would never accept such a situation and rightly blame the Tory leadership for allowing it to happen.

  • (+1) user is talking about the almost forgotten Dec 2017 agreement. Commented Sep 24, 2018 at 17:03
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    This is what the BBC have to say about the Dec 2017 agreement: "But EU negotiations always work on the principle that nothing is agreed until everything is agreed, and that raises the prospect that if the second phase runs into trouble, then what has been agreed so far could, in theory, unravel." Commented Oct 10, 2018 at 18:04
  • It may be sophistry but the talking point that it will be all the EUs fault if a border is installed in Ireland is everywhere. Something doesn't need to stand up to scrutiny to be widely accepted, all it takes is people wanting it to be true.
    – Eric Nolan
    Commented Oct 18, 2018 at 9:30
  • @EricNolan It would scupper any kind of trade deal with the EU so the UK would have much bigger problems than the Irish border at the time anyway. With the economy falling into deep recession and companies fleeing the UK I can't see the UK government lasting long enough to get their narrative out, and whoever replaces them would be under great pressure to deal with the problem to open up trade with the EU again.
    – user
    Commented Oct 18, 2018 at 9:42

Skipping your first question (I don't know of one) and going directly to

If not, why is Theresa May not using the threat of this outcome as leverage against the EU?

It doesn't work so well as a threat. Consider the following possible actions:

  1. Ireland leaves the Good Friday deal.
  2. The European Union accepts Northern Ireland as a continuing part of the EU.

These have at least as many negatives for the United Kingdom as for (the Republic of) Ireland.

TL;DR: May won't do it because the threat is too likely to boomerang on her, given her government's reliance on Northern Irish MPs.

Northern Ireland secession

The general argument against the second option is that countries like Spain might see it as a bad precedent. But in this case, it's no longer separatists in Northern Ireland driving things but the UK. If Spain becomes more worried about the UK than the Catalans, they might drop their opposition and allow Northern Ireland to leave the UK and stay in the EU. They could describe this as the UK leaving Northern Ireland rather than Northern Ireland leaving the UK. I.e. it's the UK that is acting in bad faith, not the Northern Irish.

This does not require Ireland to annex Northern Ireland. Northern Ireland could simply secede from the UK. If the EU then allows it to join as a new country, Northern Ireland would be mostly back to the status quo. It would then be harder to travel from Northern Ireland to the UK or vice versa (or trade), but Northern Ireland maintains the same relationship with Ireland and the EU. Some of the Northern Irish may prefer this result to staying in the UK and leaving the EU even without threats to the Good Friday deal.

If Northern Island were to secede, what could the UK do? Invade? Blockade? It would have to blockade all of Ireland, which would be unlikely to receive United Nations approval. It would be sorely short of allies in that situation. Meanwhile, Northern Ireland would have the support of the EU in general and Ireland in particular.

It's not clear to me why you think this scenario would threaten the EU's legitimacy. It would be clear to everyone that the UK was not negotiating in good faith. Northern Ireland is currently part of the EU and voted to stay in the EU. If it were to choose to stay in the EU rather than in the UK, that would attack the legitimacy of the UK more than the EU. The only reasons that hasn't been considered anyway is that the UK opposes it and parts of the EU see it as a bad precedent. But in this scenario, it is only when a country leaves the EU that parts of it can stay. Since Spain is not planning to leave the EU, this doesn't really apply to them.

Political ramifications of the end of the Good Friday deal

We also should consider who the biggest proponent of the Good Friday deal in the UK is. It's basically the Northern Irish. And on whom is Theresa May relying to add just enough votes to allow her to survive a "no confidence" vote? The Northern Irish. So this threat may make it more likely that she would stop being Prime Minister. While she would technically still be a Member of Parliament (MP), this would likely end her career in leadership. As such, this threat may hit her worse than anyone else.

Of course, perhaps that result would be best for the Conservative party. May would be out as Prime Minister. Labour would likely win the resulting election. Labour would be stuck trying to negotiate with the EU. Currently, the Conservatives are split between those for and against Brexit, while Labour is united against compromise. But if Labour had the government, then those against Brexit would be against Jeremy Corbyn, who is pro-Brexit. So it would be Labour that would be splitting, while the Conservatives can criticize from the sidelines.

It's even possible that neither Labour nor the Conservatives would be able to form a government. It might be that the Liberal Democrats and Scottish National Party take enough votes to prevent either side from forming a government without them and demand an end to Brexit as their price for joining a government. That might cause both Labour and the Conservatives to split into pro- and anti-Brexit factions. The UK might end up with a pro-Brexit or anti-Brexit government that will dissolve again as soon as Brexit is resolved (terminated, negotiated, or whatever).

I remain unconvinced that Chequers has any constituency. I think that most Chequers supporters are really anti-Brexit. That's why I think it would take two elections. In the first one, Labour paints over these problems by being not-May. But then they can't find a compromise that anyone likes. Second election has people realizing that the real choices are no-deal Brexit or staying in the EU. There is no compromise that the EU will make that is preferable to both those options for most people. Eventually I think that people have to choose between the available if extreme options.

The fundamental problem is that pro-Brexit has claimed benefits that are simply unobtainable. If you ask most people if they would prefer the Chequers deal to staying in the EU, it seems unlikely that they would choose Chequers. Chequers basically keeps the unpopular policies of the EU while giving up things like a vote in EU policy.

The problem here is that neither the Conservatives nor Labour are really pro-Brexit. So there are a bunch of people who would prefer no Brexit instead negotiating Brexit, thus Chequers. To come to a real agreement, they are going to have to choose Brexit or not. The only Brexit deal that a UK government can definitely deliver is no deal. Until they realize that and vote on what really matters to people, this is going to be a political turkey.

That's why I'm saying that both the Conservatives and Labour will have to split into new parties. Because currently, there is no one representing the anti-Brexit opinion in either the government or the opposition. Only small parties like the Liberal Democrats and SNP are openly anti-Brexit.

The hardline no-deal people seem to think that they would win another Brexit election. They may be right. But the current system means that no-deal Brexit is inevitable, because there is no way to get enough votes for an unpopular compromise. Labour opposes any deal, because they want a new election that they can win. The Liberal Democrats and SNP also want the chance to make gains in a new election. Some of the Conservatives prefer a new election, because they think that Chequers is too EU-friendly. How does a deal get a majority?

Many Conservatives are anti-Brexit but stuck supporting the referendum results. However, if they lost the government, then they could use that to go back to their natural preferences. Clearly if the referendum were supported, May would have won the election. If she doesn't win, then that means that the May position, negotiating any Brexit deal that retains the free trade agreement, is not supported.

There are basically three options:

  1. No deal Brexit.
  2. Cancel Brexit and stay in the EU.
  3. Accept EU regulation without any say in it.

I suspect that pretty much everyone prefers at least one, if not both, of the first two options to the third option. Some people may prefer the third option to the first option. But those people will almost always support the second option to either of the others. I don't believe that anyone really supports the third option over the second option. So the only real chance for the third option, a Chequers-style deal is that party loyalty holds enough Conservatives that enough Labour people can switch and vote it into effect. That seems unlikely.

The problem is that if Labour (or the Liberal Democrats or the SNP) politicians vote for a compromise Brexit, they are then vulnerable to someone running against the compromise who gets both the pro-Brexit and anti-Brexit vote in the next election. Perhaps they would survive, but it wouldn't seem likely going into the vote. All the feedback would be against the compromise.

The result of this may be to empower no-deal proponents. But it's hard to see how to counter that. Beyond that, it's not necessarily so. Many people who voted Leave expressed remorse later. Remain might win a second referendum. Remain might become even more popular if the choices were Chequers and Remain. Because Chequers gives neither side anything that it wants. It's not Remain and it doesn't give the promised benefits of Leave.

Similarly, Remain versus No Deal might drop on the side of Remain. Some of the people who voted Remain didn't think through what No Deal might involve, because Leave promised that the EU would negotiate. Now that it's clear that they won't, maybe people change their minds.

Of course, it is also possible that UK pro-Brexit politicians again convince people that Leave is better than Remain. After all, who want to stay in a union with a bunch of people who won't negotiate?

I don't think that it is clear who would win a new Leave/Remain election. I'm just saying that the Conservatives are currently losing. The question may not be if Corbyn will be Prime Minister, but when and how long. For Conservatives, sooner would be better. Because they want Labour to bear as much of the burden of governing as possible while offering them as few actual benefits as possible.

Implicit threats

Even if May makes only an implicit threat, she could very well be forced by the Northern Irish MPs to then make an explicit promise to work out a deal that supports the Good Friday provisions. Because this will be really important to the Northern Irish and the opposition there is likely to use it to argue that they made a mistake when they agreed to prop up the May government in the first place. That's what political opponents do. They construe any statement as negatively as possible.

This is really the whole problem with Leave again. They took an option with the expectation of compromise. But what if the other side doesn't compromise? This is a bad bluff. And if it's not a bluff, the consequences are as negative to the UK and especially May as to the EU. She could easily end up with less leverage, as everyone would then know that she needed a deal on at least that one area.

Things might be different if the Good Friday deal was unpopular in Northern Ireland. Or if Brexit were popular in Northern Ireland. But that's not how it is. The Good Friday deal is very popular in Northern Ireland and not very important in Great Britain. And Northern Ireland voted against Brexit. It wouldn't take so much to split Northern Ireland from Great Britain.

This seems like something that May would be very careful to avoid even suggesting. It's not much of a threat to the EU except that it could lead to a situation where Ireland wasn't enforcing the customs union properly. It's far more of a threat to her. Because if she doesn't make the threat explicit, then it seems unlikely that the EU will take it seriously. But internal opponents may choose to take it seriously even if they don't believe that she will follow through. So she gets all the disadvantages of the explicit threat with none of the advantages.

If she can't even make the threat openly, how would she ever carry through on it?

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    I find your option #2 highly implausible without the UK's permission. Given that the UK would be completely outside the EU treaty system, this would essentially amount to Ireland+EU annexing NI. Can you elaborate on what that process would look like and how the EU would maintain its legitimacy?
    – Kevin
    Commented Sep 24, 2018 at 0:05
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    In your last paragraph, if no government can be formed, isn't that just playing into the hands of those in favour of hard-brexit? After all, they get what they want if there's no government to make a deal. I don't think a pro- or anti-brexit coalition is likely, since it's not really that simple. There are different flavours of exit deals and I don't see MPs joining forces with other parties to achieve something they don't want (e.g. hard brexiteers backing a Chequers-like deal or those who want to stay in the customs union backing a no-deal brexit).
    – JJJ
    Commented Sep 24, 2018 at 1:10
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    Northern Ireland is one of the most economically deprived areas of the UK, I think many in the UK would be quite happy to see it secede from the union. Describing Ireland annexing the north is a poor choice of words, re-unification is more accurate. Annexation is a term usually used in which a larger or colonial power incorporates territory that does not belong to it into its own territory, usually through military conquest. The process in which Ireland was initially incorporated into the UK would be more appropriately labeled as annexation. Not the reunification of north and south.
    – Icarian
    Commented Sep 24, 2018 at 6:29
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    As a English person I would love NI to leave, as I see the Irish problem as a problem for the Irish people maybe with a UN pease keeping force. Commented Sep 24, 2018 at 17:05
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    @IanRingrose those places don't contain a majority (or, lately, plurality) of people descended from British settlers who wish to remain in the United Kingdom. And many of those places are far from "sorted out."
    – phoog
    Commented Sep 25, 2018 at 12:07

The premise of the question is flawed, because the Good Friday agreement doesn't say anything about the border. It is not clear that instituting customs checks would imply a violation of the agreement.

Furthermore, there will be no immigration checks. EU law would not require it, since Ireland is not in the Schengen area. The common travel area predates the EU by several decades, and it will survive the UK's departure from the EU.

  • I could almost upvote this but "Since 1997, the Irish government has imposed systematic identity checks on air passengers coming from the United Kingdom and selective checks on sea passengers, and occasional checks on land crossings." Commented Sep 24, 2018 at 17:00
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    @Fizz hm, good point. Maybe there will be immigration checks. But that just undermines the premise of the question even more, since the current situation is already asymmetrical such that it is possible to enter the UK by air from Ireland without a passport check but not vice versa. There's no reason to think that extending the existing air travel situation to the land border would violate the Good Friday agreement.
    – phoog
    Commented Sep 24, 2018 at 17:03

The UK leaves the British side of the Irish border open, to comply with the Good Friday Agreement (and to comply with the UK's repeated and strenuous assurances that there would be no hard border). No customs personnel are placed there, there are no immigration checks, etc.

Under WTO rules, the UK must then also leave all other borders open, as far as customs checks are concerned. Without special trade deals, the UK must treat all other WTO members the same. This option therefore implies that the UK does not have any tariffs on any imports from anywhere. This has been described as the Singapore option (see The Telegraph or The Guardian), and it would severely disrupt large sectors of the British economy. For example, British agriculture would be history.

Immigration checks are likely to remain absent even in a no-deal scenario, as the UK and the ROI are in the Common Travel Area.


This sort of possibility has occurred to me, especially on those occasions when Brexiters have said something like "We would have no intention of establishing a border in Ireland. It would be a matter for the EU to decide if they were to establish one".

It is, of course, an entirely disingenuous rationale. If there were tariffs in both directions (the inevitable consequence of a "no deal") then it would be as much in Britain's interest to prevent goods entering Northern Ireland without the duty being paid, as it would be for the EU to prevent British goods similarly entering the Republic.

So if Britain failed to establish a border, what would there be to prevent Mercedes, BMW, Renault and Citroen routing all their car deliveries to Britain, duty unpaid, via Crossmaglen, County Armagh? Cars are obviously not a good example (since they are readily identifiable and need to be registered, making it easy for HMRC to control the situation in conjunction with DVLA) but I use them to make my point. But the argument applies to vast numbers of things from paper clips to beef cattle.

Moreover I cannot think of any way that the British government could better re-ignite trouble in Ireland than to mess around in the way you suggest. And remember this. The future will not be about GREAT Britain and LITTLE Ireland, as it has been in the past. Ireland is now part of the world's largest economic entity, with a population of 480 million. Britain will have to get used to the idea that, in future Ireland negotiations, it will be the junior party.

  • Even without tariffs, the problem exists. To abolish customs checks, you need a customs union. With a free trade agreement and non-unified customs, you have to inspect goods crossing the border to ensure that the proper tariffs have been paid on those goods that originated somewhere else.
    – phoog
    Commented Sep 24, 2018 at 17:16

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