Photographer: Jason Alden/Bloomberg

QuickTake Q&A: Brexit Gets First Challenge in U.K. Court Case

British voters, it turns out, can’t actually remove their country from the European Union. Only their elected leaders can do so. Since the June 23 referendum, the debate has turned to whether Prime Minister Theresa May can initiate the country’s EU exit without first seeking permission from Parliament. The question has sparked what could turn into a wave of legal challenges, known as judicial reviews. The first one will be the subject of a two-day hearing that begins on Oct. 15.

1. What’s a judicial review?

It’s a court proceeding to weigh the lawfulness of how a government decision has been reached. Judicial reviews provide one of the few mechanisms available for members of the public to hold the state’s most powerful officials to account. Only those with "sufficient interest" are able to bring a suit, and they must first obtain permission for their case to be heard.

2. Who brought this case?

The court has made Gina Miller, whom it calls a "concerned citizen," the lead claimant. Another party is Deir Dos Santos, a hairdresser described by his lawyer as "just an ordinary guy" who wants Parliament to have the final say. "If his rights are going to be taken away, he wants it done in a proper and lawful manner," Dominic Chambers, Dos Santos’s lawyer, said.

Will Brexit Spark a Constitutional Crisis in the U.K.? Q&A

3. What’s at stake?

Either the prime minister or Parliament must invoke Article 50 of the Lisbon Treaty in order to trigger the U.K.’s exit from the EU. The government’s position is that the responsibility rests with the prime minister. Other legal experts disagree, saying a matter of this importance must go through Parliament. One of London’s biggest law firms, Mishcon de Reya, has threatened a legal challenge if Parliament doesn’t get a say. The dispute could pit the judiciary against the power of the prime minister in a manner never seen before in British history.

4. Won’t Brexit happen no matter what?

May has pledged to respect the will of the people and carry out Brexit (though she’s in no rush). So has Jeremy Corbyn, the leader of the opposition Labour Party. But before the vote, May and most members of Parliament advocated remaining in the EU. If the U.K. continues to feel economic repercussions from its June 23 vote, who knows what could happen? Should lawmakers vote against their constituents if they believe it’s ultimately in the national interest? At some point it could become relevant whether the prime minister or Parliament is in charge of pulling the trigger.

5. What’s likely to happen?

In recent years, people challenging state actions via judicial reviews have prevailed just 1 or 2 percent of the time. In one successful challenge, the Supreme Court overruled a decision by the attorney general and permitted the Guardian newspaper to obtain and publish letters written to lawmakers by Prince Charles. But that case was small potatoes compared to the question of whether citizens will be able to use the courts to steer, delay and possibly derail the U.K.’s departure from the EU.

The Reference Shelf

  • A QuickTake explainer on what prompted the Brexit vote and the arguments used by both sides
  • A story on May’s hope for a tenure that’s not "defined by Brexit."
  • The signup page for Bloomberg’s daily Brexit Bulletin.
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