Brexit: What happens next?

Now that the U.K.’s voters have decided to leave the EU, what happens next?

Prime Minister David Cameron has said it will be up to his successor to invoke Article 50—a previously arcane section of the EU’s governing Treaty of Lisbon that allows any member to give formal notice that it wishes to exit the Union. Once that’s done, the treaty gives the U.K. and the EU two years to “negotiate and conclude an agreement”  for the UK’s withdrawal and future relationship with the Union.

Article 50, which has never before been invoked, doesn’t give any timeline for when a referendum like the U.K.’s has to be translated into a formal notice under Article 50, but EU leaders have already called upon the U.K. to move swiftly to help end the current political and economic uncertainty, The Guardian reports. It’s likely there will be some behind-the-scenes negotiation before the U.K. even gives notice, reports Politico.

Once it does, the two sides will have to decide when EU law will cease to hold in the U.K., what trade and other deals the two sides will come to and what will become of EU citizens in the U.K. and vice versa. It’s possible the EU will take a hard line with the U.K., in an effort to prevent other countries from following its lead if it seems to get too good a deal.

Of course, Cameron or his successor could also choose to reject the referendum’s result, which is generally believed to be Parliament’s prerogative under U.K. law, but it seems unlikely at this point that will happen. There’s also the possibility that, should the U.K. try, an angry EU could even try to take reports of the referendum result as an invocation of Article 50, pushing the U.K. out.SM