Thursday’s historic vote was specifically about British membership of the European Union, but subsequent events appear to have raised the question of whether the decision to leave will actually result in it happening. Here we consider some aspects of this.

Why it will happen

Constitutionally, any referendum in the UK is advisory, since Parliament is sovereign and cannot be bound, even by itself. However, in practice, any Parliament or party – or even a government – that went against the decided will of the people would find itself facing an electoral impulsion, if some constitutional collapse had not intervened beforehand. In short, Parliamentary sovereignty rests on Parliament being representative of the people.

This, more than anything else, should lead us to the conclusion that the process of invoking Article 50 of the Treaty on the European Union will take place and the UK will leave the EU in due course.

So why any doubt?

Why it might not

As the events since the declaration of the referendum on Friday morning have shown, the UK is currently in the midst of profound political uncertainty. To call it a shake-up would suggest that it’s all about rejigging of pieces, but it would be more accurate to say that nobody knows what’s going to happen and nobody knows what the rules are: everything is up for grabs.

Cameron’s resignation parks the notification of Article 50: having made notice of his resignation, he is now formally head of a caretaker administration and can claim that constitutionally he is unable to make any decisions beyond the mundane, and notification of the UK’s intention to leave the EU is very clearly not mundane. Other EU leaders have little choice but to wait, whatever they might prefer.

This means that a window of opportunity opens up for anyone wanting to avoid a Brexit. Three scenarios present themselves.

The ‘simple’ option

Given the speed with which the petition calling for a second referendum has accumulated over 3 million signatures, the least complex option might be for Parliament to use that as justification for a second vote. The Petitions Committee meets on Tuesday, and in the current turmoil move Parliament to quickly pass necessary legislation: Cameron could side-step his care-taker status by this being a non-government bill and by the government not supporting any position. If done quickly, all the existing infrastructure of the campaign groups could be re-used.

However, as with so much in life, simple options don’t work very well. Parliament will be very resistant to such an blatant effort to reverse the first vote, especially given that it would on the basis of a petition signed by far fewer people than voted to leave. The public would also very likely take a second vote in this manner as a mark of bad faith, and would respond accordingly. Rather than avoiding Brexit, it would simply harder the decision.

The ‘Scottish gambit’

Nicola Sturgeon has indicated over the weekend that the terms of Scottish devolution require that the Scottish Parliament give its consent to changes in those terms. Since Holyrood implements some EU legislation, it might be possible that MSPs use the clear Remain majority as legitimation for refusing to consent, thus blocking Article 50 notification. Some Northern Irish politicians have suggested that similar situations might apply there too.

This is unlikely to work, for two reasons. Firstly, it’s legally very unclear whether ‘withholding consent’ is the same as ‘blocking’: Scottish unhappiness with the decision might be noted, but that does not mean Westminster has to abide. Arguably, all that changes is the ultimate source of legislation in these policy domains, not the implementation, so there is no ground to block it.

Secondly, Parliament would be within its powers to amend the terms of Scottish devolution unilaterally. Clearly, so to do would likely push Scotland much closer to independence, but given the mood right now, even if that doesn’t happen, Scotland might be out of the Union in any case.

Northern Ireland is potentially more complex, but the legal challenge is even weaker here and, moreover, is dwarfed by the issue of re-casting the Good Friday arrangements, which no one appears to have found a viable solution to.

The ‘hanging over the abyss’ option

The most complex manoeuver is the slowest of the three and requires a high degree of selflessness by various individuals, but might offer more of a democratic sheen to matters.

The starting assumption is that the coming weeks will be a relatively clear vindication of Project Fear: economic turmoil, diplomatic chaos and increasing numbers of Leave voters regretting their choice. Against that backdrop, a putative Tory leader might be able to take the position that – with regret, but with the best interests of the nation at heart – they no longer feel that they can support Brexit, especially on the 52-48% margin. They then work with a sympathetic Labour party to engineer a vote of no confidence in the government and go to the polls as soon as possible.

While it might be possible to do this now, if the main candidates could agree on it, the likely backlash by Tory backbenchers and their subsequent support for a Brexiteer pur et dur means that this would have to wait for the leadership contest to be finished. With the two lead figures – Theresa May and Boris Johnson – both more pragmatic than visceral in their European position, this might be possible and even credible as a ‘conversion’, following the ‘I’ve now see things from the inside and it’s much worse than we thought’ approach.

Parties would then have a choice: would they make it a manifesto commitment that any return to power would mean non-notification of Article 50 (still on hold in this scenario) or, more conditionally, a second referendum? Here the selflessness aspect kicks in, as UKIP would be expected to win many seats from both Conservatives and Labour, although very unlikely enough to have any role in a government, coalition or otherwise.

All this leads either to a government with a manifesto commitment not to notify or to hold a second referendum, which could also have threshold requirements appended, to make it more legitimate/harder to leave the EU (depending on how you saw it). In that case, one would expect that a lot would be made of how the country has suffered over the period since the first vote and that the scaremongering is actually just being realistic.

So what will happen?

As each of these scenarios suggests, many things have to fall into place and many politicians have to change their minds, burn a lot of bridges and generally be ready to take a huge hit to their reputations with the public. Any option that results in the UK not pursuing Article 50 by this autumn is at best highly unlikely and we might usefully put more effort into working out how to manage that process.