The only legally binding way to leave the EU is by notifying the intention to leave, as per Article 50 of the Treaty on European Union. Is this what you mean?

@BrunoParga Anything which is legally binding which leads to this could also count

@ChadwickMiller Would you have resolved YES after the Brexit referendum when the government announced they would respect the result?

None of that was legally binding but it feels well within the spirit of this question

@ChadwickMiller could you please give examples of things that, if they happened, would cause you to resolve yes? Other legally binding ways to leave the European Union?

I ask because as long as Article 50 is not triggered, there can be as many referendums and declarations and whatever - the country is not leaving, and continues to be bound by EU law. So I guess what I mean to ask is what you mean exactly by "legally binding".

Worth noting that even Article 50 is reversible until it takes effect, two years after it is triggered. The UK asked for an extension of that period and it was granted by agreement of all other members.

(disregard this comment)

@JoshuaWilkes Yes I would resolve that to Yes

Related https://manifold.markets/MrLuke255/will-poland-still-be-part-of-the-eu?r=TXJMdWtlMjU1

Will Poland still be part of the EU in 2030?

93% chance. Resolves YES if Poland remains in the EU at least until the end of 2030.