The United Kingdom voted to leave the European Union — but getting out is getting complicated.
The U.K.'s high court ruled Thursday that the government can't officially notify the EU it wants to leave without the approval of Parliament.
It's up to the U.K.'s Prime Minister Theresa May to invoke Article 50, informing the European Council the country wants out.
Article 50 is a part of The Lisbon Treaty that allows members of the European Union to withdraw membership.
But needing Parliament's approval might be a setback for May. The prime minister planned to invoke Article 50 by the end of March 2017. The new power shift could throw off that timetable, which has frustrated some government officials.
Once the Article 50 button is pushed, the U.K. will have two years to complete negotiations with the EU.