There was a custom's border inside France from 1815[0] to 2008, with different treatment for imports/exports from Switzerland to the small part of France beyond that custom's border.

According to that article, you can still buy cars w/o EU import duties in that part of France...

[0]: Yes, as a result of Napoleon's defeat and as part of Geneva joining Switzerland.

Because it's a slippery slope that looks very much like ceding territory. It's not just border checks, but Northern Ireland would be effectively in the EU as far as customs rules and tariffs. Otherwise, you could circumvent the EU tariffs by importing in the UK, moving the goods "internally" to NE then loading them on a truck and unloading somewhere in the rest Ireland.

This differentiated regime would strengthen economic ties with Ireland and weaken those with Britain.

A hard border, combined with the overwhelming preference of North Irish to remain in the EU, increases the chance of a successful North Irish referendum for unification with Ireland. If the UK allows such a referendum and Ireland unifies, then the UK is ceding territory anyway. So there's really a no-win scenario assuming that the UK leaves the EU customs union.

If the UK wanted to commit a further violation of the Good Friday Agreement and act to prevent an Irish reunification referendum, or ignore the results of one, the Troubles would very likely start all over again, and the UK would be in no position to negotiate any kind of cease-fire because they would have demonstrated twice over that they can't be trusted in such things.

I don't think that the Good Friday Agreement does say this, I would like a reference if you can provide one.

The alternative isnfor the UK and ireland to simply refuse to enforcr a hard border and dare the EU to do it if they are so upset about customs.

What, is the EU going to station troops there, because of trade deals?

Neither Ireland or the UK are interested in enforcing any sort of hard border. It is instead the EU who would become unhappy about broken trade deals.

But that means Britain effectively has an open border with the EU (which Brexiters don't like, and probably some Remainers don't like in the context of Brexit though they are happy with it with UK a full member of the EU with a say in union policy), or has an internal border between NI and the rest of the UK (which pretty much no one in the UK likes.) The EU has a similar problem with Ireland where the UK has NI.

Which is why this issue is intractable; it internally has no good solution on either side, even before the difficulty of getting agreement between the sides. This is worse on the UK side, because of the interaction with the Good Friday Accords; it's not just abstract political displeasure, it's potentially undermining an internal peace agreement.

The UK and Ireland do not want a hard border. That is a fact. They aren't going to enforce it.

It is irelevant to point out the consequences, because both sides have stated that they will never ever ever enforce a hard border.

The UK and Ireland would both be perfectly fine with not having a hard border. They have stated as such.

You can call it dumb or say that it undermines the purpose of brexit, but at the end of the day it doesn't matter. Both Ireland and the UK are willing to accept the consequences of not having a hard border no matter the consequences.

It's pretty relevant, because the UK government doesn't have Parliamentary support for either of the alternatives, given Brexit, to the the thing they say they won't do, and also seems (though surprises are possible) to be likely to prevent Brexit from being derailed even if they can't pass a Brexit deal. So it's quite likely that we’re heading to a Brexit with none of the choices regarding the Irish border being politically viable.

That political choice is "don't do anything about it, and leave it without a hard border". And this is the choice that both the UK and Ireland want to take.

That would be (from the UK side) the effective open border with the EU choice.

> And this is the choice that both the UK and Ireland want to take.

No, Brexit with the Irish border as an end-run around Britain’s new EU border is not a choice that has majority Parliamentary support in the UK.

For example, the US has, for years, refused to pass any kind of immigration reform, but until recently, also refused to comprehensively enforce the immigration laws already on the books because they were really awful and unfair in places. For another example, neither the People's Republic of China nor the Republic of China (effectively Taiwan) recognize each other, and yet Taiwanese businesses own tons of factories in mainland, PRC-controlled China.

I thought half the point of Brexit was so that the UK could secure it's borders.

And they are just going to leave their biggest land border wide open?

Hopefully yes. I don't want to eat some toxic food that nobody checked when it entered the EU.

IE, they would become the target of terrorist attacks. I doubt they would want this to happen to them.

Ireland would absolutely, under no circumstances, enforce a hard border. They would simply refused to do it.

If the vast majority of people in NI are happy to be part of the EU customs zone and allowing them their wish (in the spirit of the Good Friday Agreement) also allows brexiteers to turn the rest of the UK into a Singapore (Reece-Mogg) or a Venezuala (Corbyn) as they see fit without any encumberance from the EU, then what's the problem?

I just don't get it. A year ago, some of the leading voices of the Brexit movement were advocating special customs zones to be set up around the UK, once free for EU competition rules. There were news stories with brexiteers advocating a Tyneside Customs zone, for example. Why is it fine for Tyneside to be have a separate customs zone to the rest of the UK but not Northern Ireland?

> All it requires is that the UK accepts that EU customs checks are performed between Britain and Ireland ... I have no idea why the extreme brexiteers find this idea so objectionable?

Generally they don't. However the government is only in power with the support of the DUP[0] who see it as THE END OF THE WORLD, and it would be a complete anathema to Ulster loyalists[1], whose are (essentially) half of the Good Friday Agreement.

In short: if they accepted this, the British government would fall and armed conflict could well break out again in Northern Ireland.

[0] https://en.wikipedia.org/wiki/Democratic_Unionist_Party

[1] https://en.wikipedia.org/wiki/Ulster_loyalism

Overall to Brexit supports in Britain it doesn’t really matter, it mainly matters politically for the current government. Without the DUP they would effectively be a minority government.