Ask Full Fact: Brexit in court

Q: What do you mean, Brexit in court?

A: A number of different people are challenging the way in which the Prime Minister plans to implement the referendum vote to leave the European Union.

These different legal actions have now resolved themselves into two main cases. One is about whether Parliament needs to pass legislation before the UK can leave, and the other is about the effect on devolved governments.

Q: Why two different cases?

A: One’s in England, the other in Northern Ireland. They have separate High Courts.

The second case involves some arguments specific to Northern Ireland, such as the contention that the province should have to agree to Brexit because of the Good Friday Agreement.

The High Court in Belfast reportedly wanted to make sure that the regional angle got a hearing. It put the issue being debated in the English case on hold.

Q: Isn't that one about trying to stop us leaving the EU?

A: Not directly. The lawyers in the English case say that’s not the motive. They’re arguing that the government can’t make the decision to take us out of the EU on its own.

Instead, they want the courts to declare that MPs and members of the House of Lords have to authorise it first.

Q: Hang on, hasn’t the decision to leave the EU already been taken?

A: People have voted for it (although only a minority in Northern Ireland and Scotland), but the referendum wasn’t legally binding. Formally, nothing has changed. We’re still a member of the EU and the government has not yet triggered the process of leaving.

We only begin that process when we inform the EU that the decision has been taken.

Q: By invoking Article 50 of the Lisbon Treaty, right?

A: Actually it’s Article 50 of the Treaty on European Union. But, yes, according to Article 50, a country that wants to leave the EU has to notify the European Council, which is made up of government leaders. That kicks off a period of negotiation on unwinding that country’s membership, which is a complex business.

Q: So it’s up to the Prime Minister to do that?

A: That’s what the government’s lawyers think, and plenty of other legal experts as well. But equally respected lawyers disagree, saying that Parliament would have to authorise the use of Article 50 by passing legislation. Now the courts will have to decide.

Q: How can it be such a difficult question?

A: Article 50 says that a country’s decision to leave the EU has to be made “in accordance with its own constitutional requirements”. The UK doesn’t have a codified constitution—the president of the Supreme Court thinks it doesn’t have a constitution at all—which leaves plenty of scope for argument about what our “constitutional requirements” are.

Q: Can you give me the opposing arguments in one sentence?

A: One side says “Under the UK’s constitution, it is the Crown (the Queen acting under the Royal Prerogative in practice on the advice of government ministers) which has the power to enter into and withdraw from international treaties”.

So on this view, the government has the power to trigger Article 50.

The other side says that there is an existing law, or statute, making EU rules part of our legal system, so “it is not open to government to turn a statute into what is in substance a dead letter by exercise of the prerogative powers”.

If they’re right, Parliament would need to have a say.

Q: So which side did the judges take?

A: Neither, yet. The case began on 13 October in front of the Lord Chief Justice, Lord Thomas of Cwmgiedd, sitting with two other judges.

Whichever side loses is expected to appeal. But it’s likely that the appeals will ‘leapfrog’ the Court of Appeal and go straight to the UK Supreme Court for a hearing in December. That court would be expected to deliver its judgment before the end of the year.

The government made it clear in court that it wasn’t planning to trigger Article 50 in 2016. Theresa May has since confirmed that it will happen by the end of March 2017.

Q: Let’s have the rundown of the different cases, then.

A: The lead claimant in the London case is a fund manager called Gina Miller. She’s represented by Lord Pannick QC and the solicitors Mishcon de Reya.

Other challenges have been combined into her case, including a claim brought by a hairdresser named Deir Dos Santos and a “People’s Challenge” crowdfunding campaign organised by Grahame Pigney, a UK citizen who lives in France.

The case in Belfast also consolidates different groups. One challenge was launched by Raymond McCord, who campaigns on behalf of victims of violence in Northern Ireland. The other involves a group of activists and politicians from various parties.

Q: Who are they taking the case against?

A: The government, essentially, but cases of this kind are brought against a specific minister. The newly-created Secretary of State for Exiting the European Union, David Davis, has this on his plate.

Q: If the claimants win, will MPs and peers have to vote in favour of Brexit for it to happen?

A: Yes.

Q: And if the claimants lose?

A: Theresa May will be able to trigger Article 50 at a time of the government’s choosing and on its own authority.