Why is it impossible to leave the Single Market without a hard Irish border?



I see a repeated assumption that puzzles me. From another well asked and answered question:

On one hand it is impossible for the UK to leave the Single Market while maintaining an open border with an EU member

The comments and answers point out that both the Irish and the UK do not want a hard border, so why is it impossible to leave the Single Market without one? I presume the EU cannot legally force a country that is not a member to enforce its border with them and it can't force the UK to remain an EU member if it decides on a soft border.

This question also includes the assumption and has an answer titled "They can't" but the reasons it gives aren't things that create impossibilities. For example, it claims:

any Brexit implies stricter borders

Maybe for Ireland/EU but the UK does not have to impose any border restriction. It seems to be assumed, and yet it's been a soft border for almost 100 years:

the border is essentially open, allowing free passage of people since 1923 and of goods since 1993

I'm looking for something of the ilk of a technical/legal reason, not one that is about negotiating stances or consequences or political inconveniences that go "against Brexit". I'll give 2 examples of things I'm not looking for and why because I want this to be a very strict question.

  1. Negotiating stance: The EU demands it or it refuses to sign a trade deal. That doesn't make it impossible even though the UK could concede to it, the UK could simply ignore it.
  2. Consequence: (From this answer) The UK would have to accept the free flow of EU citizens over the border. If foreigners can master the Ulster accent well enough to hide illegally then good for them! ;-) But, this also doesn't make it impossible.

It's an assumption so often made and rarely challenged that I'm very curious to find the answer. It appears to be the EU's problem entirely as it would threaten their customs union and that they are the ones that require a hard border after Brexit. However, maybe I missed something obvious or there's an international law I'm unaware of that makes it so?


Posted 2018-03-04T05:05:42.077

Reputation: 664

11By definition if the UK leaves the single market it'll end up with a border. The question revolves around how hard that border will be. At one end the UK is adamant about refusing freedom of movement and ECJ jurisdiction - i.e. it'll necessarily end up being a hard border. At another respecting the Good Friday agreement mandates a soft border in Ireland. And yet another the UK wants no border in the Irish Sea. Having all three at the same time is unlikely if not possible. – Denis de Bernardy – 2018-03-04T07:44:18.743

@DenisdeBernardy How would refusing ECJ jurisdiction affect the hardness of the border? – iain – 2018-03-04T16:22:08.530

4@iain: Because the Council, the EC, and the EP all made it clear that ECJ jurisdiction was a sine qua none condition to getting a soft border. – Denis de Bernardy – 2018-03-04T16:46:20.183

1"I presume the EU cannot legally force a country that is not a member to enforce its border with them" – While true, the EU can just enforce the border on its side of the border. – Daniel – 2019-08-09T22:43:37.943

@Daniel That could be true, but as Ireland's Taoiseach has repeatedly said (in the Irish parliament and beyond) Ireland will not put up a hard border. I'm wondering how the EU (as a separate institution to the Irish government) would do it in those circumstances? – iain – 2019-08-10T08:23:10.240

@ian, The Republic of Ireland is still part of the EU and as such has to respect decision of the ECJ. The EU could simply take Ireland to court to force them to implement a border (court sanctions could be fines or economic sanctions until the matter is resolved). Ireland would have only a few choices ... pay the fines forever, implement the border, or also leave the EU ... – Hoki – 2019-09-12T11:31:28.517

@Hoki They could go that route, though that would undermine the statements the EU has made about putting up a border and make them to "blame" for it, which would be politically unpalatable. I'm sure they'd prefer the UK to take the rap for a hard border. – iain – 2019-09-12T12:39:55.117



I'm looking for something of the ilk of a technical/legal reason, not one that is about negotiating stances or consequences or political inconveniences that go "against Brexit". I'll give 2 examples of things I'm not looking for and why because I want this to be a very strict question.

  1. Negotiating stance: The EU demands it or it refuses to sign a trade deal. That doesn't make it impossible even though the UK could concede to it, the UK could simply ignore it.

Actually, there is a technical/legal reason why that's backwards. If there is no trade deal, World Trade Organisation rules effectively require there to be a hard border. I suppose you could say that it's still possible because both the UK and the EU could leave the WTO or drop all tariffs on imports, but that would be deep into the ridiculous.

The issue is that the WTO restricts discrimination. The first principle of the WTO trading system is

Most-favoured-nation (MFN): treating other people equally

Under the WTO agreements, countries cannot normally discriminate between their trading partners. Grant someone a special favour (such as a lower customs duty rate for one of their products) and you have to do the same for all other WTO members.


Some exceptions are allowed. For example, countries can set up a free trade agreement that applies only to goods traded within the group — discriminating against goods from outside. Or they can give developing countries special access to their markets. Or a country can raise barriers against products that are considered to be traded unfairly from specific countries. And in services, countries are allowed, in limited circumstances, to discriminate. But the agreements only permit these exceptions under strict conditions. ...

On a narrow technical level, it would be possible for the UK to leave the Single Market and the Customs Union and have a customs union similar to the EU-Turkey one but more comprehensive: i.e. complete free movement of goods but not people or services. The obstacles to such a deal are more political and practical (lack of time) than legal, and any legal issues could in principle be fixed were there political will and time. Absent such a comprehensive trade deal, both parties will be required to levy tariffs (or drop tariffs for the entire world), which means having a mechanism to levy them, and that means having a border.

Peter Taylor

Posted 2018-03-04T05:05:42.077

Reputation: 3 482

Hi Peter, thanks for answering, that's really interesting. Do you have a link to the WTO rules that specify this? (or know where I might look?) – iain – 2018-03-05T14:22:06.030

@iain, I'll expand with a quote from a WTO web page. – Peter Taylor – 2018-03-05T14:37:27.360

5Additionally, this trade deal would probably likely be almost completely reliant on the UK's acceptance of rules made within the EU - politically unacceptable to many if not most brexiteers. – Miller86 – 2018-03-05T16:16:01.720

@PeterTaylor I'm going to look into that, thanks for adding that. I know you're far behind on votes here but this is by far the best answer given the parameters I set. Thanks for making that effort too. – iain – 2018-03-05T17:50:43.987

I think that even if MFN didn't apply (and having read up on it, it's possible it wouldn't, exemptions are made, legal challenges are mounted etc) this still answers the question best, and I hope in the long run it garners more votes than the others, which seem to be attracting votes because of the topic itself rather than the quality of question. Which is sad to see on a Stack site. – iain – 2018-03-06T13:58:12.223

9For what it's worth, I'm not sure if you've seen global politics lately, but knee deep (or neck deep) in the ridiculous is sort of par for the course these days... – corsiKa – 2018-03-06T15:34:23.043

The WTO has said that there is nothing in its rules that would force either the EU or UK to erect a hard Irish border after Brexit. https://www.irishtimes.com/news/ireland/irish-news/wto-says-its-rules-would-not-force-eu-or-uk-to-erect-hard-irish-border-1.3710136

– trapper – 2019-02-27T04:26:17.333

4@trapper That's not a fair summary of the article. What it's saying is that the WTO won't actively enforce its rules, but will wait for another WTO member to make a complaint. Which will happen almost immediately, when other countries see Irish exporters to the UK getting more favourable treatment than their own countries' exporters. – Mike Scott – 2019-02-27T14:07:26.710

@MikeScott there is no WTO rule requiring a hard border though. The lack of hard border doesn’t mean Ireland will get any favourable trade terms - so no problem. – trapper – 2019-02-27T14:31:58.457

3@trapper How can you charge tariffs without checking at the border to see what tariffs are due? You can have trusted trader schemes and pre-submission of paperwork, but without border checks you can't stop lorries crossing the border without having done that paperwork. The WTO rules don't say "there shall be a hard border", but it's hard to see how you can follow them without having one. – Mike Scott – 2019-02-27T14:39:18.243

1@MikeScott I do agree it will be difficult to prevent all smuggling, but this is generally the case anyway. My point was just that WTO rules do not require a hard border, and there isn’t going to be one – trapper – 2019-02-27T14:48:31.537

@MikeScott MFN (now I've had the chance to read up on it:) is about favouratism, not hard borders, so you have to match how you approach trade with others. That does not necessitate a hard border, especially when checks are low (figures on imports to Ireland, for example, show they check between 2-6% of goods). That's still a lot of goods but if there were fewer/no tariffs, more automation in paperwork etc then it's certainly possible. Possible doesn't make it so though… it'd be good if it was sorted out soon! – iain – 2019-02-28T00:36:29.540

Why is dropping tariffs completely such a ridiculous idea? – Vikki - formerly Sean – 2020-04-28T00:47:21.513


In the strictest sense, it is of course possible; but it doesn’t make any sense, unless Brexit is only for symbolism.

The whole point of Brexit (beside the symbolism) and of leaving the single market and the customs union is to allow Britain to act independently from its former partners – at least in trade issues. On the other hand, one main point of a single market is to allow goods to be traded as seemlessly between, say, Madrid and London as they traditionally are traded between Manchester and London; there should be no trade barriers in a single market.

So let’s consider some scenarios where Brexit Britain starts doing its own thing while the Irish border remains fully open:

  • The British parliament and government decide, in order to protect the British strawberry growers from unfair (sunnier) competition, to introduce a 200% import duty on strawberries. (This is a tariff barrier.) The meaning is that strawberries bought for £ 2 a kilogram in Spain should cost at least £ 6 when reaching England. However, importers take their Spanish strawberries to Dublin (no import duty because single market), then across the Irish border to Belfast (no import duty because fully open border), then to England (no import duty because of the UK’s own internal single market), and sell for £ 3. The British strawberry growers and the government aren’t happy.

  • The British authorities decide to allow treating chickens with chlorine. This is not allowed in the EU, and chlorinated chickens aren’t supposed to be in circulation within the EU. (This new regulatory divergence between Brexit Britain and the EU amounts to a non-tariff barrier.) However, Northern Irish farmers take their chlorinated chickens to the Republic (possible because fully open border) and sell them to supermarkets there, and in other EU members. The EU and its remaining member states aren’t happy.

  • The president of the US, Donald Trump, likes Brexit Britain so much that he generously exempts it from his 25% import duty on steel. Belgian steel works transport their produce via Ireland and Northern Ireland to the US, avoiding the duty that is supposed to target them. President Trump isn’t happy.

Of course, Brexit Britain could refrain from utilizing its newly-found power to diverge, voluntarily keeping the rules that the EU has. That, however, would mean “a Brexit in name only”, i.e. pure symbolism.


Posted 2018-03-04T05:05:42.077

Reputation: 5 559

82And despite this being incredibly simple to understand, and having been repeatedly spelled out to the British public (both before the referendum and since), plenty of people still think it’s all just lies and somehow the realities of global trade can somehow be magicked away. – eggyal – 2018-03-04T15:30:52.080

Thanks for the response. Wouldn't the UK give subsidies to strawberry growers instead while reaping the benefits of cheap strawberries? Tariffs are not the only means of protectionism. As to the EU being unhappy, so what? I don't mean that callously, I mean that it's simply not a concern (or strong concern) of the UK, as I mentioned in my question. – iain – 2018-03-04T16:34:40.593

9@Iain Subsidies are more expensive than tariffs, though, and the government don't have a magic money tree! – owjburnham – 2018-03-04T16:49:06.690

22@iain: It may be true that Britain doesn’t care about the EU’s happiness, but I gave three examples specifically to show that Britain and the EU and even third parties may be negatively affected. (And the third party matters to Britain, too, because it will react like this: “If you can’t stop our generous trade agreement being exploited by EU traders, we’ll need to repeal it.”) – chirlu – 2018-03-04T16:56:00.310

6Note that the same arguments also apply to free movement of people as well as goods, meaning that no border in Ireland means effectively free movement between Britain and the EU (though it is easier to deport people back to their origin than chicken) resulting in some of the legal immigration being converted to illegal immigration. – Kaithar – 2018-03-04T19:01:01.303

2@Kaithar - There's nothing to stop the British authorities putting in place passport checks at the seaports in the western UK. The facilities are already there, they just need to be expanded somewhat. I suspect immigrants won't find the porous Irish border nearly as obvious or easy a route into the UK as you seem to think. – Valorum – 2018-03-04T20:33:41.347

11@Valorum That could prevent people from going to Scotland/Wales/England from Northern Ireland. But don't forget that if you're in NI, you're already in the UK. Besides, I don't think the legal citizens that have to cross the Irish sea regularly would be too happy about suddenly having to go through passport checkpoints. – Jorn Vernee – 2018-03-04T21:39:53.873

@JornVernee - Self-check-in (done via the internet) could be done by the overwhelming majority of travelers. More than two thirds of travelers have a UK passport that could be checked before they even leave for the ferryport, done when they purchased their tickets. That leaves just a few thousand per day, a number which could be handled by just a handful of border guards. – Valorum – 2018-03-04T22:13:23.890

@JornVernee - You might also want to note that illegal immigrants sneaking in through N.Ireland are probably quite easy to spot on the Mainland ferry since 98% of the population are Caucasian and have broad Northern Irish accents. – Valorum – 2018-03-04T22:24:20.267

@chirlu Yes, but those 3 examples are outside of the parameters of the question and frankly, I don't think they hold up - but we're all allowed our opinion. However, your first line addresses it completely "In the strictest sense, it is of course possible" so right now you're on course for the tick :) – iain – 2018-03-04T23:39:20.760

@owjburnham There is no magic money tree. However, there would be massive savings (at least) because there are no customs checks, which would more than pay for any subsidy (and that's just one way it would benefit the UK). It's best not to look at these things in isolation. – iain – 2018-03-04T23:49:48.553

@JornVernee "I don't think the legal citizens that have to cross the Irish sea regularly would be too happy about suddenly having to go through passport checkpoints." Maybe they would if they know the alternative is a hard border with Ireland. Chance of bombs vs a quick scan of your passport - which would you choose? – iain – 2018-03-04T23:51:08.563

9@iain Passport control isn't just an inconvenience; it's a political symbol generally associated with borders, particularly since the UK is not otherwise known for internal ID checkpoints. Many people firmly believe that a trip from Belfast to London should be no different than one from Manchester to London. – Zach Lipton – 2018-03-05T04:15:12.697

1@ZachLipton I agree. How many of those people a) Want to invalidate the Good Friday Agreement? b) Want violence to break out again? c) Are living in NI? d) Want to leave the UK? I'd wager it's a very, very low number. I also think it's a low chance passports will be checked much more than they are now. – iain – 2018-03-05T04:52:25.093

37"There's nothing to stop the British authorities putting in place passport checks at the seaports in the western UK." <--- and thus you make a hard border in the Irish Sea :) This particular configuration leads to NI feeling like a second class citizen within the UK and triggers complications further down the road. In the short term, the DUP will say hell no and May will need to find more votes from Labour to get things passed. – Kaithar – 2018-03-05T07:05:36.243


Regarding putting passport checks in the Irish Sea (i.e., from NI to Mainland UK) - It's worth pointing out that the people who would be vehemently opposed to this (the NI Unionists) are currently the only thing keeping Theresa May's government in office (by forming a coalition with the minority Tory party). Good luck with riling them... http://www.parliament.uk/mps-lords-and-offices/mps/current-state-of-the-parties/

– Oscar Bravo – 2018-03-05T09:30:47.120

5Another point is that no EU country is allowed to have its own individual trade agreements - all member states must abide by EU wide regulations. This means that the EU will not allow Ireland to have its own non-standard border rules with Northern Ireland, which could be seen as an individual rule that is beneficial just to Ireland. – Qwerky – 2018-03-05T10:31:01.760

4@Valorum That 2% of not caucasian will be hard to spot and what you suggests will prompt racism issues. Also will the (unknow)% of illegal caucasian immigrants slip through? – jean – 2018-03-05T11:14:19.290

@iain "Wouldn't the UK give subsidies to strawberry growers". Maybe. that has it's own problems. Say the UK starts heavily subsidizing an industry and exporting to the EU through ireland. Competing firms in the EU get no subsidy and eventually get driven out of business. Then the UK ends the subsidies and raises prices.


Currently the EU has rules that bind member states to prevent them from doing things like this to each other. Hard brexit would leave no replacement.

– Murphy – 2018-03-05T14:26:37.403

@Jean - Profiling is very effective in detecting potential illegal immigrants when more than 98% of travelers across that border are white Britons. White non-Britons with a right to be in the UK can usually be detected by their not speaking English natively but invariably traveling with a valid passport. This means that the "hard border" will be undetectable by more than 99% of travelers – Valorum – 2018-03-05T14:52:17.237

16@Valorum I do wonder what the DUP (and the rest of the world) will make of a system with two passport queues, one of which says "White with Ulster Accent Only" – pjc50 – 2018-03-05T15:33:54.480

26As for passport controls: that presumes everybody has a passport or an ID card, which is not the case in the UK. It's perfectly possible not to have a passport, and if that would exclude one from travelling in one's own country, that would not be popular. – Oliver Mason – 2018-03-05T15:37:20.487

3Putting passport checks on the NI-Great Britain crossing would force Northern Irish people to get a passport, which they currently don't need. Overall the effect is to make more Northern Irish people think "Maybe I'd be better of being part of a country I could drive to and gives me access to the whole of Europe than one where I have to take a ship and get my passport checked." – DJClayworth – 2018-03-05T15:43:21.923

3@Valorum Wrong again. It will, at best, detect imigrants, not ILLEGAL imigrants and the racism issues will be not worth it – jean – 2018-03-05T16:19:27.697

1@Jean - You seem to be conflating sensible border controls with racism. – Valorum – 2018-03-05T17:42:08.697

1@pcj50 - Alas, we live in a world where people want to get into our country because it's nicer than theirs. At some point you have to have a border. At the moment it's nicely tucked away in Turkey and so forth but with Brexit, Britain will need it's own border. – Valorum – 2018-03-05T17:44:12.287

@Murphy I think that's possible but unlikely as the market would be global without the protectionism of the EU around the UK. Still, I'm against subsidies in principle, I just find it a bit vexing that in all these answers people are setting up what amount to straw men by not being willing to look at the range of possibilities, so I pointed it out. – iain – 2018-03-05T17:54:41.647

7@Valorum You seem to deny profiling based on skin color is racist – jean – 2018-03-05T18:40:16.043


@jean - Profiling on the basis of skin colour is an excellent way of detecting illegal immigrants from Africa and the middle-East. Or should every little old Irish granny on the ferry be subjected to the same checks just to satisfy political correctitude?

– Valorum – 2018-03-05T18:52:51.287

14@Valorum Besides being racist, it's ineffective (what about illegal immigrants from Europe who won't be detected by your profiling?) and over broad (what are you going to do to, say, a British citizen of Asian heritage who doesn't have a passport and wants to travel between two parts of his own country?) – Zach Lipton – 2018-03-05T19:08:41.320

@ZachLipton - Taking your straw(Ulster)man at face value, I suspect the only solution you'd be happy with is unrestricted travel between Europe (e.g. Eire) and Northern Ireland. Since that policy led to a colossal rise in both illegal and legal immigration, I suspect that restricting entry requirements will prove to be a popular move with most who voted to leave (e.g. the majority of voters). – Valorum – 2018-03-05T19:11:29.873

11@Valorum You seem to want to impose a passport requirement for people with dark skin but not for Irish grannies, but we'll gloss over the fact that you didn't address either of the practical difficulties I cited with your profiling plan. As has been pointed out above, a hard border across the Irish Sea is not an acceptable option to the DUP, which is the party in coalition maintaining the current government. It may be popular with you, but the DUP's opposition poses a political problem...and this is the politics StackExchange after all. – Zach Lipton – 2018-03-05T19:24:45.430

@ZachLipton - There may be other ways to satisfy the requirement for border control without the need for a passport such as the presentation of a birth certificate at a post office. Also, you seem to be ascribing opinions to the DUP that they don't hold. They're aware that a border (of some kind) will be needed and they're not daft enough to imagine that it'll be wide open – Valorum – 2018-03-05T19:26:11.703


@Valorum Is there a requirement to present a birth certificate at a post office to travel from Manchester to London? No. Which makes this precisely the kind of measure that is unacceptable to the DUP, and they will stop supporting the government.

– Zach Lipton – 2018-03-05T19:30:41.227

@ZachLipton - As I said, any political or practical solution will be unwelcome to those who don't want a solution. – Valorum – 2018-03-05T19:32:49.747

6@Valorum Everybody wants a solution but not everybody will risk harass decent innocent people based in skin color/religion/gender/heritage/etc. Also there are flaws in your plan others have pointed out – jean – 2018-03-05T19:50:16.903

1@jean - There are always flaws in every plan. The present passport system in use at airports clearly discriminates against poor people since it acts as a £7 a year surcharge on flying. If you wait until a plan is perfect before enacting it, you'll be waiting a very very long time. – Valorum – 2018-03-06T00:04:23.737

13@Valorum A hard border between NI and the UK breaks the Good Friday agreement against the Unionists. A hard border between Ireland and NI breaks the Good Friday agreement against the Republicans. Those arrangements are part of a larger settlement agreed in good faith and which largely stopped decades of violence from both sides. Neither side will accept that agreement being broken now - especially if it is just their half that gets broken - but as pointed out above it's also impossible to Brexit without breaking one side or the other. Yet another warning the brexiteers ignored... – Tim B – 2018-03-06T09:26:15.810

6@iain what possibilities? You don't seem to have provided any. You just keep sorta going "naaaahhh I don't think that matters" every time someone points out glaring, massive problems. You seem to be only looking for confirmation of what you want to believe rather than any honest answer. Your definition of "properly" seems to simply be "that confirms what I want to believe regardless of reality" – Murphy – 2018-03-06T11:45:58.893

4@iain: it’s worth bearing in mind that chirlu’s examples also apply in reverse, so while you may not care about the EU being upset by the second example, what if the EU were to permit chlorinated chickens that Britain do not want (or any other goods the U.K. wishes to control)? An open Irish border prevents the U.K. from controlling the flow of such goods into its markets, thereby undermining the whole “taking back control” argument underlying Brexit. – eggyal – 2018-03-06T12:22:53.087

@eggyal There was I thinking that the UK was going to lower standards across the board and that the EU did everything better, or so I'm told. I'm also told that the UK will stay in very close regulatory alignment. In either case, your the reverse position is moot. – iain – 2018-03-06T13:55:01.407

3@iain: if by “very close regulatory alignment” (or certainty that EU regulations will always be more stringent than British ones) you mean that the U.K. will continue to abide by all EU regulations, then you are quite right but as chirlu said that would be “Brexit in name only”—no different to the U.K. pre-Brexit except it would lose all influence over EU decision-making. – eggyal – 2018-03-06T14:32:42.240

@eggyal I think you need to spot the sarcasm and irony in my comment ;-) Anyway, I'm not here for a debate, feel free to upvote the answer you think is best. It's not this one IMO. – iain – 2018-03-06T14:44:30.337

@Valorum Plans are not perfect but must at least work for some extend your will not work and also can backfire because you are just being unfair to a perfect legal group of the population and once you broke justice for one citizen the law's empire broken. Also theres something above law on dealing with illegal immigrants called ethics and moral. You just cannot close eyes to a humanitarian crysis. The bottom line is immigrants will find they way in and how you will deal with these people will reverbere in future for good or bad – jean – 2018-03-06T20:22:40.907

2@jean - The concept that vast levels of immigration are simply something that has to be accepted (like bad weather) is one of the reasons why the public voted to leave the EU. Immigration can be controlled if one has the political will to control it. – Valorum – 2018-03-06T20:25:26.837

1@Valorum Bad thing most people voted brexit because immigration and brexit will do nothing to stop it. In the end was only a lie was told to sell a ridicule move. And you don't have to accept immigration as you don't have to accept miserable british weather but if you live here you will have both =) – jean – 2018-03-06T21:16:41.997

4@TimB Just a wee note on terminology: When discussing the convoluted affairs of Northern Ireland, it's important to get the terms of address correct. The opposite of Unionist is not Republican. Those who argue from a legal, political perspective are called Unionist and Nationalist.Those who cross the line into armed conflict (i.e., paramilitaries) are called Loyalist and Republican. – Oscar Bravo – 2018-03-07T07:03:51.000

In practical terms isn't there already a hard border of sorts between NI and Britain? I mean, is it actually possible to travel to/from NI legally and the rest of UK without carrying any sort of id at all? – Lembik – 2018-03-07T10:50:48.433

@OscarBravo Thanks, noted. It's too late to edit my comment now but I'll try and remember that for the future. – Tim B – 2018-03-07T11:49:43.073

2@Valorum I'm guessing you've never stopped to consider why these "vast" numbers (a few hundred thousand a year against a population of 65 million, LOL) of illegal immigrants are braving hazardous and often fatal treks in an attempt to reach the UK. Or what could be done to discourage them from doing so. After all, it's far easier to put the problem out of sight and out of mind, than it is to actually solve it. – Ian Kemp – 2018-03-07T12:05:00.807

2@IanKemp - I have greatest sympathy for asylum seekers. Most illegals arriving in the UK have, however, traveled through safe countries to get here. – Valorum – 2018-03-07T12:24:24.373


@IanKemp "I'm guessing you've never stopped to consider why these "vast" numbers (a few hundred thousand a year against a population of 65 million, LOL) of illegal immigrants are braving hazardous and often fatal treks" 1. "LOL" is not a dignified response to anyone on this subject 2. You've misquoted Valorum anyway. A straw man is also undignified. 3. If you'd researched it instead of considering it without evidence you'd realise it's because of EU law restricting safer ways. https://www.youtube.com/watch?v=YO0IRsfrPQ4&t=35s

– iain – 2018-03-08T00:41:34.727

@Lembik it's dependent on the company. Some require photo ID but each company can set itself what it needs. The important thing is that you'll likely find a company that just requires some sort of ID, which means they'll accept a birth certificate, which every citizen is entitled to and probably owns, and if they don't they can get a new one for a tenner. – Louise Davies – 2018-03-08T16:50:13.947

@Valorum There's nothing to stop the British authorities putting in place passport checks at the seaports in the western UK. There is. It's called the Democratic Unionist Party and it's the party that is keeping the current UK Government in power. There would be wigs on the green if you even hinted to them you were thinking about dreaming about maybe, perhaps, even possibly introducing any form of control between Northern Ireland and the Rest of the United Kingdom. Their entire reason for existence revolves around the concept that NI is the UK. – Oscar Bravo – 2019-08-27T14:30:22.023


The EU has customs at its borders. This allows it to, for example, collect tariffs on imports from the USA. So suppose the EU sets a 10% tariff on US cars. Now when a car moves from the US to Belfast, the UK collects a tariff. The UK can then re-export the car to Dublin, and there is no tariff because the UK and Ireland (the republic) are in a customs union.

Now suppose the UK leaves the customs union, and negotiates a trade deal with the US, which allows for free trade in cars between the UK and the US. If the Irish border remains completely open, then a US exporter could bypass EU tariffs by exporting to the UK and then re-exporting to the EU through Ireland. It would make a hole in the EU customs border.

International trade is a big enough deal that just "not enforcing" is not an option. Either Northern Ireland remains in a customs union, or the EU would have to impose some form of customs control at the border.

There has to be a customs border somewhere. The question is where:

  • In the Atlantic? (Not acceptable to UK government)
  • Between Northern Ireland and the Republic? (Breaks Good Friday Agreement; not acceptable to Ireland)
  • In the Irish sea? (Breaks Good Friday Agreement; absolutely unacceptable to the UK government)
  • In the English Channel? (Ireland leaves the EU, absolutely unacceptable to Ireland)

Every option breaks someone's red lines.

James K

Posted 2018-03-04T05:05:42.077

Reputation: 70 324

1Could add that a border in the Irish Sea is not only unacceptable to the UK government, but also violates the Good Friday Agreement. – gerrit – 2018-03-04T14:30:10.963

"International trade is a big enough deal that just "not enforcing" is not an option." - why? If the UK says it won't raise tariffs then it's not enforcing by making them irrelevant to the UK. Which then obviates the "There has to be a customs border somewhere." bit. That's what I'm interested in finding out - what is the has to or must. – iain – 2018-03-04T16:38:05.730

23@iain borders are bidirectional. The UK can say what it likes about exporting to the EU, but the EU also has a say in what it imports from the UK. If the UK has a better trade deal with another country, that country might find better profit by exporting to the UK then taking it across the non-border to Eire. That's going to deprive EU states of import taxes. And if the UK doesn't have better trade deals, what's the point in "leaving so we can negotiated our own deals"? – Kaithar – 2018-03-04T19:07:36.213

2@JamesK That is simply not factually correct. – iain – 2018-03-04T23:40:15.800

@Kaithar There is more to life than money (or so I'm told) so to take trade deals as the only variable would probably end up with an incorrect analysis of that. – iain – 2018-03-04T23:42:10.693

3@iain There is more to life than money, but trade deals is one of the major rallying cries of the Leavers... that we'll be able to negotiate better trade deals for ourselves once we're out of the EU. – Kaithar – 2018-03-05T07:07:44.707

Very clear and concise explanation of the necessity and consequences. – Trilarion – 2018-03-05T09:22:16.897

@Kaithar I agree. It is also not the only reason given, and anyone doing an analysis that ignores this will almost certainly produce a wrong analysis. That's a general rule with any subject. – iain – 2018-03-05T10:03:43.740

@gerrit which part of the Good Friday Agreement would be violated by customs controls between Northern Ireland and the rest of the UK? I've read it a few times and I see nothing. James K the same is true of a customs border on the Irish land border. The GFA says nothing about it. – phoog – 2018-12-22T10:54:26.387

1@phoog I'm not sure. I've read it somewhere. I could be wrong. – gerrit – 2018-12-23T21:35:52.113


One of Theresa May's red lines is that the UK must be able to do its own trade deals with other countries. This is not compatible with a soft border in Northern Ireland, because those trade deals (like all trade deals) are certain to include a requirement that the UK controls the import of goods to make sure that goods shipped from the UK to the country in question are genuinely from the UK and haven't slipped into the UK from a country not included in the trade deal, such as Ireland. Similarly, the EU's existing trade deals with other countries don't allow it to let goods from the UK into the EU unchecked.

Mike Scott

Posted 2018-03-04T05:05:42.077

Reputation: 2 446


After brexit both the EU and the UK will have its own borders. In principle you should not think of this as a single border but as one border exiting the EU and another border entering the UK or vice versa. This actually used to be the case between most countries with a part of no-mans land in between. Each country has full control over its own borders unless otherwise negotiated or in violation of international law.

For practicality both borders are usually combined into a single border.

In the case of a hard brexit with the UK refusing to close its border the EU (of course all presumed) will presumable impose a hard border on all incoming goods and people while not caring about the outgoing. So in this way the EU can impose a one-way hard border on the UK. The UK of course can do similar thing with its own border.

D.J. Klomp

Posted 2018-03-04T05:05:42.077

Reputation: 71

But couldn't the UK and the EU have a border and still be in the same single market? – Trilarion – 2018-03-05T13:40:44.080

3Note that the NI border runs through the land and in some cases houses of quite a lot of people. – pjc50 – 2018-03-05T15:30:11.927

1@Trilarion If the EU and UK are in the same single market but not a customs union, there not only can be a border, there has to be. That's the situation with Norway and Switzerland, which both have a hard border with the EU (for goods; people just get waved through, since both countries are in Schengen). It requires both a single market and a customs union for there to be no border controls on goods. – Mike Scott – 2019-02-27T14:01:40.310


Having no hard borders is the very definition of the single market. If the UK leaves the single market, then it would require consent from both the UK and the EU not to implement a strict border. This mutual consent would take the form of a treaty, e.g. with Switzerland being a member of Schengen, yet not being an EU member.

So, in theory it would be possible for the UK to leave the single market and having no hard irish border, if the UK and the EU agree to do so. However, this would only work as long as the UK's economic regulations remained compatible to the EU's single market.

Dohn Joe

Posted 2018-03-04T05:05:42.077

Reputation: 2 365

3The Swiss model will not work because (1) it has a guillotine clause that forces the Swiss to accept EU workers, or else ALL deals are bust. The Swiss voted themselves immigration quota running foul of this and had to give in! (2) The EU doesn't like the model, so it's unlikely it will repeat it. Refs on request. – Fizz – 2018-07-21T10:03:22.877


The EU can impose that Ireland maintains a hard border regardless of the UK's involvement. They can impose this to protect the trade agreements of the single market from either directly or indirectly benefiting the UK.

By contrast, a soft border cannot protect the trade agreements of the single market from benefiting the UK, nor can it protect against the exploitation of any of the UK's future trade agreements.

Edit: To reflect a direct answer to the question posed, it's not impossible by the literal definition of the word, there are no universal rules/laws when it comes to trade and borders between countries, everything can be negotiated and decided upon. The issue solely revolves around negotiation with the EU and can be solved if all parties come to agreement. The position is seen as practically impossible, a semantic use of the word to emphasise the extreme unlikeliness of any such agreement.


Posted 2018-03-04T05:05:42.077

Reputation: 37

2Please source the claim that the EU can impose 'hard borders', and quote the relevant section. – Chloe – 2018-03-05T04:56:13.973


@Chloe - No individual EU country is allowed to make its own trade deals - http://ukandeu.ac.uk/explainers/trade-deals-with-third-countries. A soft border between Ireland and NI could be seen as an individual trade deal for Ireland and as such is not allowed.

– Qwerky – 2018-03-05T10:34:27.313

1@Qwerky "A soft border between Ireland and NI could be seen as an individual trade deal for Ireland" - Any official word on that? – iain – 2018-03-06T04:15:44.057

3@Chloe TFEU, Title V, Chapter 1, Article 67, Subsection 2: "It ... shall frame a common policy on asylum, immigration and external border control, based on solidarity between Member States, which is fair towards third-country nationals." -- The EU Member States collectively agree to the EU border. – Xpndable – 2018-03-06T09:12:04.813

1@Xpndable A common policy isn't the same as a hard border everywhere, that's the beauty of wording it in the abstract. That's how EU directives work, after all. Is there a source that sets out the implementation detail i.e. must be a hard border ? – iain – 2018-03-06T14:02:44.593

2@iain My point wasn't that they have to have a hard border, my point is it isn't the UK or Ireland's choice to make. As borders are bi-directional, and Ireland doesn't get to make the choice, both the UK and Ireland are still bound by what the other EU members decide and agree upon (and if no new agreement can be made, existing policy stands - a hard border). The burden falls to the UK to persuede the EU to assist Ireland in bargaining for a border policy, lest they be seen as doing nothing, and blame falls to Brexit as the cause of this border issue. – Xpndable – 2018-03-06T15:27:33.263

1Also, if Ireland has no checks on goods entering from the UK, but doesn't have a comprehensive trade agreement with the UK, then WTO rules mean it can't have checks on any of its imports from any country. You're not allowed to discriminate between WTO members like that. And the same applies to imports to the UK from Ireland, of course. – Mike Scott – 2019-02-27T14:03:28.807


The EU cannot legally force a country that is not a member to enforce its border

True, but the Republic of Ireland is a member of the EU, so the EU can force them to enforce a border with the UK on their side. Even if the UK would let anyone in like before, would you call a border which can be crossed freely one way but not the other a "soft border"? Besides, it's very unlikely to happen in practice, because one of the key points of leaving the EU was for the UK to reclaim its right to reinforce their own borders.

Dmitry Grigoryev

Posted 2018-03-04T05:05:42.077

Reputation: 1 190

Yes, I would call it a soft border because it's soft on the side that matters to the UK with respect to the claimed problem. If Ireland were forced to harden the border (I'd love to see that tried) then the EU would have to take the blame, something it does not want. As to the "right to reinforce their own borders", it's possible to want a right but not use it in every situation. You can want the right for free speech but never say anything controversial, the application is separate from the autonomy aspect. – iain – 2019-04-02T08:01:34.257