1. The Brexit referendum has no legal standing in terms of Britain exiting the EU. This point has been made repeatedly, but it is worth emphasizing: The only reason Britain is preparing to leave the E.U. is because British Prime Minister David Cameron said Britain would leave if a majority voted for “Leave” in the Brexit referendum.
Legally, Britain leaves the E.U. when the British government triggers Article 50 of the Treaty on European Union. To be very clear, the results of the Brexit referendum do not automatically trigger Article 50. Therefore, the referendum itself does not legally produce a British exit from the E.U.
And ironically, one of the very first things David Cameron did after the referendum was announce that his government would not trigger Article 50; instead, he said would resign — in a few months — and let the new government trigger Article 50. But again, we can see that referendums don’t trigger opt-out clauses in treaties: Governments trigger opt-out clauses in treaties.
2. In Britain, Parliament is sovereign. In some ways, this is a corollary to the first point — that the Brexit referendum has no legal standing. But it is still worth stressing that, as is written on the website of the British Parliament:
Parliamentary sovereignty is a principle of the UK constitution. It makes Parliament the supreme legal authority in the UK, which can create or end any law. Generally, the courts cannot overrule its legislation and no Parliament can pass laws that future Parliaments cannot change. Parliamentary sovereignty is the most important part of the UK constitution.
If and when it happens, the decision to trigger Article 50 will ultimately be made by a British government. Under the British parliamentary system, the “government” is ultimately responsible to Parliament, and more specifically to the lower house of Parliament, the House of Commons. If a majority of Parliament no longer has “confidence” in the government, there are mechanisms by which the government can be replaced.
This raises a conundrum. What happens if a majority of the House of Commons opposes Brexit, and a future British government seeks approval to trigger Article 50 from the House of Commons? Similarly, what happens if a new election to Parliament is held, and members specifically run on opposition to Brexit? Would they feel obligated to support Brexit because of the referendum — or would they feel obligated to honor their election pledges? More generally, could some members of Parliament conclude that the principle of parliamentary sovereignty — “the most important part of the U.K. constitution” — trumps the results of a referendum supported by 52 percent of voters?
3. Sometimes constitutional changes require more than a majority to pass. In the Brexit vote, “Leave” won because it received a majority of the vote, which is defined as at least one more vote than half the votes casts. While Britain famously does not have a written constitution, the decision to leave the E.U. has the feel and gravity of a constitutional change. And while majority vote is certainly a popular way to decide an up-or-down question, it is not the only way, especially when constitutional changes are being considered.
Constitutional change could instead require a “supermajority” of, say, 60 percent of the vote, or even two-thirds or three-quarters of the vote. For example, in the United States. if members of the legislature want to propose an amendment to the Constitution, a two-thirds vote in favor is required. In many European countries, supermajorities are in fact necessary to amend the constitutions. Clearly, Brexit was not pitched as requiring a supermajority to proceed, but this question might nevertheless be raised as a way of questioning its legitimacy. An online petition that was launched before the Brexit vote — which now has over 4 million signatures — calls for a second referendum if the first Brexit referendum failed to yield a 60% vote for either side.
4. Sometimes constitutional changes require more than one vote to pass. Brexit passed in a single vote. In the days since that vote, the media has featured many — admittedly anecdotal — stories of people claiming to have regretted casting their vote one way or another. One way to deal with such “regret-xit” would have been to schedule two referendums and require that both pass before Britain would leave the E.U. This would have given people a chance to ruminate over the first-round results, and then have an opportunity for a “do-over” if, for example, they were more interested in seeing “Leave” do well in the election than in actually having Britain leave the E.U.
5. Sometimes constitutional changes have sub-national as well as national vote requirements. A joke making the rounds sums up this concern nicely: “An Englishman, a Scotsman and an Irishman walk into a bar … The Englishman wanted to go, so they all had to leave.”
This point represents perhaps the most serious challenge to the implementation of Brexit. Can Northern Ireland and Scotland be forced to leave the E.U. even though a majority of their citizens voted again Brexit?
Exactly this kind of concern is hard-wired into the U.S. process for amending the Constitution: Constitutional amendments are valid only after they have been passed by three-quarters of the states (either in the state legislatures or state conventions).
To give another example, Australia allows referendums to be used to amend its constitution, but requires what is known as a “double majority“: a majority of people in a majority of states and a majority of the total vote. On these grounds, Brexit would have failed, as “leave” achieved a majority of the vote in only two out of four regions: England and Wales but not Scotland and Northern Ireland (or Gibraltar, for that matter). Thus what Max Fisher calls “the Scottish Veto” is out there as a possibility.
6. Triggering Article 50 seems to be a terrible way to begin negotiations for any country. When political scientists study bargaining, a key concept is the “reversion point,” or the state of the world if no deal is made. If both parties are likely to be better off with an agreement than the reversion point, a deal will likely be made. If one party is better off at the reversion point than with a deal, then a deal likely will not be made.
However, if the reversion point is significantly worse for one party than the other, then that party is disadvantaged in the negotiations: The party with a terrible situation at the reversion point is likely to desperately want a deal, and the other party is likely to know that. It seems to me that this situation might very well describe negotiations over Britain’s exit from the E.U. According to a February 2016 briefing from the European Parliament,
If no agreement is concluded within two years, that state’s membership ends automatically, unless the European Council and the Member State concerned decide jointly to extend this period.
In other words, Britain’s reversion point during negotiations will simply be to revert to no relationship with the E.U., which does not seem to be anyone’s goal in this process at all. This in turn suggests that once Article 50 is triggered, Britain may find its negotiating position substantially weaker than in previous rounds of negotiating its relationship with the E.U. from within the union. Which, of course, may have been the point of structuring Article 50 this way in the first place.