Legally binding backstop..

drunkmonkey

How rock solid is one of it was agreed on the border, what's to stop the UK from renaging, the threat of legal action?
It looks like a bad idea as there hardly going to agree to something in the future they won't agree to now.

Peregrinus

International Treaties are legally binding (like a contract is) and there can be sanctions for breaking them (like there can be when you breach a contract).

The usual sanction is, of course, loss of the benefit of the Treaty - if you don't perform your obligations under the Treaty, you may find you can't insist on your rights under the Treaty.

Sometimes a Treaty will include a mechanism for arbitrating disputes and complaints under the Treaty, which may include referring complaints to an international tribunal that might, e.g., order the offending state to pay compensation or make some other form of restitution. That's relatively unusual, of course.

The injured state also has the usual range of measures available to it, from sending a note of protest, to expelling diplomats, withdrawing co-operation in other areas, etc.

Realpolitik plays a big role here - How badly is the injured state actually injured? How likely is it that measures of this kind will bring the offending state to heel? Etc, etc.

And, finally, there is reputational damage to states that flouts treaty obligations. How likely are you to want to do a deal with Teapotistan, or be willing to make concessions to secure a deal from Teapotistan, if Teapotistan is known to ignore the obligations it has accepted when it tires of them?

There is a real issue with the backstop in the Withdrawal Agreement. Once the transition period expires (and assuming it is not extended) the UK doesn't derive any great benefit from the Withdrawal Agreement. Therefore, if they walk away from what is left of the Withdrawal Agreeement, i.e. the backstop, they are not bothered about losing the benefits of the WA. At that point, it has no benefits for them.

Ireland isn't really in a position to apply sanctions to the UK. The EU certainly is, and I think would be disposed to, but if relations are already poor and, for example, no future trade deal has been agreed between the EU and the UK, the scope for this may be limited and the UK may decide that its not bothered by the possible loss of co-operation from the EU, if they don't have much co-operation from them to begin with.

Of course, there's the reputational damage, but in the scenario we're lookign at the UK would already have suffered a fair degree of reputational damage. And you can't lose the same reputation twice.

The bottom line is that if things really go pear-shaped between the EU and the UK there is limited damage to the UK in walking away from the backstop, and not a huge amount the EU could do in retaliation. In that scenario the UK can pretty much do what it likes. Freedom, as Bobby McGee used to say, is just another word for nothin' left to lose.It's like you might choose to breach a contract if the money you will lose/damages you will have to pay are not big enough to concern you.

Which is why its very much in Ireland's interests that things should not go pear-shaped between the UK and the EU. What we want is a UK/EU relationship which, on a continuing basis, delivers favourable, beneficial terms to the UK. That gives them something to lose if they walk away from the backstop.

So, bottom line, if there is a Withdrawal Agreement with a backstop, and the UK does leave under that agreement on 29 March next, and attention then turns to negotiationg the future relationship between the UK and the EU, expect Ireland to be an early and enthusiastic proponent of Don't Let's Be Beastly to the British. We'll be all in favour of their getting a sweet, sweet deal, as long as it preserves the open border in Ireland.