On June 23, 2016, the government of then Prime Minister David Cameron held a referendum on whether the UK should remain a member of the European Union. Of the 72 percent of eligible voters who cast ballots, 51.9 percent voted in favor of leaving the the EU. The unexpected outcome, which resulted in Cameron's resignation, will have a profound impact on the UK's legal system and is likely to dominate UK politics and lawmaking for years to come.
Cameron's successor, Theresa May, announced that her government would initiate the process of withdrawing from the EU by the end of March, 2017, without holding a vote in Parliament. This decision prompted a legal challenge. On November 3, 2106, a three-judge panel of the the High Court of Justice ruled that the government must obtain Parliament's consent before it can initiate the withdrawal process. The government appealed the ruling. On January 24, 2017, the Supreme Court of the UK upheld the decision of the High Court, forcing the government to introduce a bill in Parliament authorizing the UK's withdrawal from the EU.
The House of Commons passed the withdrawal bill without alteration, but the House of Lords attached two amendments. One would have unconditionally guaranteed the rights of the 3 million EU citizens who currently reside in the UK prior to the start of withdrawal negotiations, and the other would have given Parliament the opportunity to reject the terms of the withdrawal agreement negotiated by the government and force it reopen negotiations with the EU. When House of Commons declined to back either amendment, the Lords backed down and approved the original bill.
On March 29, 2017, Prime Minister May issued a formal notice of the UK's intention to withdraw from the EU to Donald Tusk, the President of the European Council, thereby triggering a two-year period of withdrawal negotiations. Key issues to be determined during the course of the negotiations include whether, and to what extent, the UK will retain access to the EU's single market and whether, and to what extent, the UK will be able to curtail the free movement of EU citizens within its borders. In a speech delivered on January 18, 2017, the prime minister indicated that her government would prioritize immigration controls over single market access.
Equally daunting are the constitutional challenges posed by Brexit. Some legal scholars contend that a general election should be held before the negotiations begin or that a second referendum will be needed to ratify the final withdrawal agreement. Most significantly, Brexit could result in the dissolution of the UK as a unified political entity. Nicola Sturgeon, the first minister of the devolved Scottish government, has stated that she will seek a second referendum on Scottish independence prior to the UK's withdrawal from the EU if Scotland's interests are ignored during the course of the withdrawal negotiations.