Thread by @Usherwood

Leaving treaties, a quick guide

1/

The international system is a bit of wild place and to a surprising degree, what goes, goes: you get to do quite a lot that you want (although conditioned by what others might do in return)

However, that said, there is some structure

2/

There are some general conventions about international treaties, which closely map on the more-interesting-than-it-sounds Vienna Convention on the Law of Treaties (VCLT)

3/

Lots, but not all, states have signed up to VCLT since 1969, but it's a good rough-and-ready guide to what polite society might consider the rules of it all

4/

You can read it all here: treaties.un.org/doc/publicatio…

We're going to focus on Section 3 "Termination and suspension of the operation of treaties"

4/

There are various grounds for leaving a treaty, but the key bit for our purposes is Art.54

5/

Basically, it's saying if a treaty has rules about leaving, then you follow those. If it doesn't then you find common agreement between the parties (via procedure set out in later provisions of VCLT)

6/

Let's take an entirely non-random example: the Treaty on European Union

Does it have any rules about leaving?

Why yes, it does

Art.50

7/

So under VCLT (and, by extension international custom in general), the way you can leave the EU is being following Art.50

8/

As you'll see, once a state submits its intention to leave (the first two paras), there's absolutely no power for the EU and the other contracting parties to stop it happening

You only need their agreement for any deal you might agree under Art.50(2)

9/

The Treaty doesn't provide for a state to give any power to other states or the EU to limit its power to leave

Nor does VCLT

Nor does international custom

10/

Even if the UK wrote a law to give any its power to decide to withdrawal (which it hasn't and won't), it has no way to enforce it, because the UK's writ stops at its borders

11/

Just to complete the thought, under the EU's legal framework (the Wightman ruling), the UK also has a unilateral right to stop its withdrawal.

So both leaving and staying in are just down to the UK

Alone

By itself

12/

In sum, EU can't have any power to stop the UK leaving the treaties

/end