This Guardian article argues about connections between Cambridge Analytica and Brexit referendum.

There is a paragraph that tells us about some restrictions related to how information and money can be used for political campaigns in Britain:

Beyond data, there are two more issues at stake here: overspending and coordination between campaigns. The law forbids campaigns from coordinating, to forestall the potential for shell entities and overspending vehicles. In the digital age, where political campaigns use Facebook as their predominant tool, it’s difficult to enforce. And when four different campaigns – Vote Leave, BeLeave, Veterans for Britain and the DUP – all used the same data firm, AIQ, it’s pretty much impossible.

Assuming that the vote leave campaigns indeed broke some electoral rules (through an official investigation), does this change anything related to the referendum results? Or the referendum results cannot be changed (e.g. it is considered null and must be repeated).

If I understood correctly, from EU's perspective triggering article 50 was the point of no return for Brexit, but whether referendum campaign was done legally or not might be very important within UK. This would be particularly interesting since the referendum lead to irreversible consequences (outside UK).

Question: What happens if it is proved that "vote leave" campaign broke campaigning laws?

Important: this question is not about whether campaign was done legally or not. Not even about its nature (Brexit). It is about what campaign regulations specify in such cases (illegal elements in referendum campaigns).


3 Answers 3


Nothing (Legally)

Regardless of the circumstances of the referendum, the (legal) basis for Brexit is the European Union (Notification of Withdrawal) Act 2017. I will add it in its full form so we can discuss all of the intricate details:


An Act to confer power on the Prime Minister to notify, under Article 50(2) of the Treaty on European Union, the United Kingdom’s intention to withdraw from the EU. [16th March 2017]

Be it enacted by the Queen’s most Excellent Majesty, by and with the advice and consent of the Lords Spiritual and Temporal, and Commons, in this present Parliament assembled, and by the authority of the same, as follows:—


Power to notify withdrawal from the EU

(1) The Prime Minister may notify, under Article 50(2) of the Treaty on European Union, the United Kingdom’s intention to withdraw from the EU.

(2) This section has effect despite any provision made by or under the European Communities Act 1972 or any other enactment.

Short title

This Act may be cited as the European Union (Notification of Withdrawal) Act 2017.

That's all folks! Not much to argue about, isn't it? No "Because of the results of the referendum" and much less "Assuming that the referendum was conducted according to law". No preconditions to argue about if the Act allows for Brexit or if it does not.

Also, nothing in the law organizing the referendum stated that the results were to be automatically implemented. And even if that was the case, since the UK system works with Parliamentary supremacy1, that new Act alone would be enough to legalize Brexit, regardless of what the referendum law said. The fact that an Act (or any other law) is based on wrong or even false premises does not invalidate it legally2.

Of course, if some new information appeared that substantially weakened the pro-Brexit position (be it that the referendum results were directly false -ie. "Remain" won but the results were manipulated, or that science proves that the UK will sink under the sea the day after Brexit), at the political level it would be possible for Parliament3 to change its stance. Which would lead to the additional issue (see here and here) that the EU does not have a stablished procedure for cancelling the invocation of Article 50, so that would have to be worked out, too.

It is complicated (Politically)

Not all cheating is equivalent. More to the point, the current alegations mean that even if campaign rules were broken, people did vote freely and the results match the votes that were cast. This makes any claim for invalidating/ignoring the results very difficult and almost pointless, because:

  • it is difficult to impossible to prove the relationship between the rule being broken and the result (i.e., would the result have been the same wihtout cheating?).

  • people who became convinced to vote one way or the other are unlikely to change their vote because of financing rules violations; if some piece of info/propaganda convinced me that the best option is X, the fact that such piece was "over-budget" does not affect my conclusion. Compare that with other possibilities like ballot stuffing or buying/threatening voters.

And of course, automatically invalidating referendums for any violation of the rules is problematic, too:

  • Just get some underlyings to break some law while supporting the opposing side and you are set: if the referendum goes your way you won; if it does not then you are able to invalidate it.

  • If the results change, the people on the losing side are going to be very pissed, and even some people in the winning people are going to be worried about the whole issue.

  • Last but not least, a (posible) repetition of a referendum would be slow and expensive.

which advises to accept the results of a referendum (or any other votation) unless you have more than enough evidence to support that the violation of the rules did alter the results.

1 You might remember that shortly after the referendum there was a legal battle because the Government claimed that it had authority to initiate Brexit by itself, but it was ruled that since it affected many British laws the authority of Parliament was needed.

2 In other countries, maybe a false premise could lead to an opportunity for a law to be invalidated on grounds of conflict with the constitution or other higher level laws, but in the UK the constitution is not written and emanates (among others) from the Acts of Parliament, there are no "higher laws" that could be used to invalidate an Act.

3 Maybe it would be only necessary for the Government, since the Act does not mandate the Brexit process but only allows it. But legal details aside, it would be suicidal for any Government to cancel Brexit without Parliament's support.

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    "be it that the referendum results were manipulated" in illegal ways, of course, because the very purpose of campaigning is to manipulate the voter.
    – RonJohn
    Commented May 2, 2018 at 18:04
  • If the outcome of a referendum (especially if it were legally binding) were caused by breaking campaigning laws - and if (hypothetically) that referendum were precisely about changing campaigning laws or their enforcement then the inability to dismiss the referendum and its consequences (a "legislative undo") would mean the perpetrators would get away scott-free - this seems very dangerous.
    – Dai
    Commented May 3, 2018 at 4:20
  • 1
    I'd suggest an edit for the sake of accuracy / more detail: the 'no constitution' issue is really "the UK has no mechanism for judicial review of laws on 'constitutional' grounds". We do have constitutional laws and precedents, but they just don't get treated the same way as in a country with entrenched laws / judicial review.
    – owjburnham
    Commented May 3, 2018 at 10:01
  • 2
    I agree with most of this. One nit: it has not yet be determined whether Britain can unilaterally cancel Brexit; a number of well-informed people believe it is possible. (It would need a judgement from CJEU to determine that). Commented May 3, 2018 at 10:23
  • 1
    While it may not affect the withdrawal, certainly individuals could be prosecuted for the laws they broke.
    – sirjonsnow
    Commented May 3, 2018 at 15:00

The referendum was conducted under the terms of the Political Parties, Elections and Referendums Act 2000, somewhat modified by the Political Parties and Elections Act 2009.

On a quick reading, the most relevant part appears to be

118 Special restrictions on referendum expenses by permitted participants.

(2)Where any referendum expenses are incurred by or on behalf of a permitted participant during any such period in excess of any limit imposed by Schedule 14, then—

(a)if the permitted participant is a registered party falling within section 105(1)(a)—

(i) the responsible person or any deputy treasurer of the party is guilty of an 
 offence if he authorised the expenses to be incurred by or on behalf of the party
 and he knew or ought reasonably to have known that the expenses would be incurred
 in excess of that limit, and

(ii) the party is also guilty of an offence;

(b)if the permitted participant is an individual falling within section 105(1)(b), that individual is guilty of an offence if he knew or ought reasonably to have known that the expenses would be incurred in excess of that limit;

(c)if the permitted participant is a body falling within section 105(1)(b)—

(i)the responsible person is guilty of an offence if he authorised the expenses
  to be incurred by or on behalf of the body and he knew or ought reasonably to
  have known that the expenses would be incurred in excess of that limit, and

(ii)the body is also guilty of an offence.

The schedules attached give the figures in question and an indication of how severe a sentence would be attached if the authorising person is convicted.

I certainly can't find anything suggesting a referendum would be overturned, which isn't surprising, since UK referendums are advisory, with no legal power in of themselves, so that there isn't really anything to be overturned in the case of a discredited referendum except public opinion.

  • Can a UK referendum be given legal power? Michael Gove tells us on the Radio 4 "Today" show on 01 May 2018 at 2:18:08 "the democratic will of the people [...] who have given us an instruction." Not advised us, but instructed. Commented May 2, 2018 at 19:24
  • 6
    @AndrewMorton There was a fudge implemented for the AV referendum in 2011, where the act of parliament authorising the referendum also listed what would happen in the event of a yes vote. The equivalent bill for the 2016 vote didn't, so Michael Gove's language was let us say, poetic. en.wikipedia.org/wiki/… en.wikipedia.org/wiki/European_Union_Referendum_Act_2015
    – origimbo
    Commented May 2, 2018 at 20:23
  • 6
    @AndrewMorton: Unless I'm severely mistaken, "giving instructions" is just as binding as "advising". Neither are legally recognized terms (in this context), and as such their use in political speech is not to be taken as legally enforceable.
    – MSalters
    Commented May 3, 2018 at 7:53
  • @MSalters The EU referendum legislation merely required the relevant bodies to run the referendum and report the results, whereas the AV legislation actually had consequences contingent on the outcome of the referendum. "Advisory" and "giving instructions" are just descriptive terms - they don't appear in any of the legislation.
    – James
    Commented May 4, 2018 at 9:53

There's no precedent for this in British Law, so what would happen is anyone's guess.

If it turned out that these allegations were true and moreover that such alleged manipulation led to serious doubts about the results of the referendum then a second referendum may be called by Parliament.

There is such a precedent set at the European level: Denmark held a referendum on the Maastricht Treaty in 1992, this was rejected. After the provision of four exceptions in the treaty, the treaty was again subject to a referendum the following year, and this was accepted.

  • 4
    The second Maastricht treaty referendum in Denmark was a completely different situation. There were no serious concerns about the legitimacy of the 1992 referendum. They repeated it because the terms of the treaty had changed. The hypothetical situation described in the question is a different one. Nothing changed regarding the meaning of Brexit, but the legitimacy of the referendum itself is questioned.
    – Philipp
    Commented May 3, 2018 at 11:36
  • 1
    @Phillip: Sure; referendums by their nature are rare, so it's unlikely to find exact correspondances; the point I was making is that it's useful to look at the European level to see what precedents have been set. Commented May 3, 2018 at 12:38

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