As I write this, British voters are deciding a referendum on “Brexit,” Britain’s potential exit from the European Union. By the time you read it, we might know how the the electorate went. Over the last few weeks leading up to the vote, you’ve undoubtedly read articles warning of dire consequences, either of staying or leaving. You’ve followed the campaign with varying degrees of glee or horror. Within hours, we will have an answer to the big question: will Britain stay or go?

And if Britain decides to “remain,” the morning after story will be pretty boring: A political story about how the EU forces won and bested the insurgent Euro-skeptics.

On other hand, if British voters choose to “leave,” we will have on our hands one of the biggest international law stories of modern times. Indeed, as often happens, the most challenging questions arise the morning after, at least if Britain decides to leave. What exactly—legally speaking—does a Brexit actually entail?

As public service, I’ve done all the Googling for you so you don’t have to. It turns out that getting out of the EU—which not a lobster trap—is the easy part. The harder part for Britain will be building the relationships and institutions to replace those the EU structure provides.

The Mother of all EU Treaties

The primary document governing Britain’s withdrawal from the EU is the Treaty on European Union (TEU), as amended in 2007 by the Treaty of Lisbon. The TEU and the Treaty on the Functioning of the European Union (TFEU), which helpfully describes the two treaties as “constitut[ing] the Treaties on which the Union is founded.” Only the TEU, however, addresses withdrawal.

It does so in Article 50, which provides that “[a]ny Member State may decide to withdraw from the Union in accordance with its own constitutional requirements.” This is the Brexit vote. If Britain votes to go, David Cameron will then, per the TEU, “notify the European Council of [Britain’s] intent to withdraw.”

But as I say, withdrawal is the easy part. Once this notification is made, the real work begins. The TEU provides that the “Union shall negotiate and conclude an agreement with [the departing] State, setting out the arrangements for its withdrawal.” Withdrawal isn’t effective until either this agreement is approved by a qualified majority of the European Council or until after two years have passed.

While this two-year time limit can be extended by unanimous vote of the European Council (with Britain’s agreement), it is conceivable that the two-year period could run without a final agreement having been reached.

Just One Treaty? That Doesn’t Seem So Bad.

Most of the big treaties and agreements underlying the European Union have been incorporated into the TEU and TFEU. For example, signatories of the TEU are bound, unless they have otherwise opted out or limited their involvement, by the Charter of Fundamental Rights of the European Union, the treaty establishing the European Atomic Energy Community, and the Schengen Agreement (establishing passport-free zones; this is one of the treaties Britain never joined). The TEU also encompasses the Maastrich Treaty, which created the euro, though again, Britain has never signed on to this portion of the agreement.

As a result, the big issue may not necessarily be which subsidiary treaties Britain has to withdraw from — withdrawal is basically automatic after giving notice — but which treaties Britain now needs to make to replace those it has left. The answer is that the country will have its work cut out for it.

The tasks can generally be broken down into three groups.

New Agreement with the EU

As discussed, Britain will need to enter into a new agreement with the EU. The major issues here will be trade, specifically access to the single market, and control over migration. The TEU answers a lot of questions: Take away those answers and you have a lot of unanswered questions you have two years to address. Indeed, everything covered by the EU treaties would need to be considered and potentially replicated, including topics like agriculture, services, atomic energy cooperation, and any number of other areas. Switzerland could be a model here; its relationship with the EU is governed by more than 120 treaties and agreements.

New Agreements with Other Countries and Organizations

Currently, at least some portion of Britain’s relationships with non-EU countries are governed in varying part by treaties between the EU and those other countries. Trade agreements come immediately to mind, but these sorts of treaties can touch on a wide range of subjects. Turkey and the EU, for example, signed an agreement in 2013 regarding the readmission of individuals living without authorization within either the EU or Turkey. Britain would therefore need to make plans to replace these relationships or agreements once it left the EU. There are a lot of them.

Similarly, there are some organizations or international arrangements in which Britain currently participates through the EU; Britain would likely need to establish (or at least consider establishing) its own relationships. For example, Britain is currently a party to the Food Assistance Convention, the Convention on the International Recovery of Child Support and Other Forms of Family Maintenance, and the International Coffee Agreement 2007 as a result of its membership in the EU. The EU Treaties Office provides a complete database of all the EU’s international treaties and agreements; there are about 880 bilateral treaties and 260 multilateral treaties. It’s definitely long enough to keep British diplomats busy for the next two years.

Some of the complexity Britain faces could be minimized by joining some other organization. The most obvious candidate is the European Free Trade Association. Britain was a founding member, but it left when it joined the European Economic Community. EFTA currently comprises four European countries that aren’t EU members (Iceland, Norway, Switzerland, and Lichtenstein).

Internal Laws

According to the House of Commons Library, anywhere between 15 percent and 55 percent of Britain’s laws come from, or are based on, EU law (the ranges depend on whether, or to what extent, EU regulations are considered laws). The level of influence and control varies depending on the topic — for example, the EU makes the supreme law on “industrial, agricultural, and commercial life” across the EU, while it has minimal role in laws relating to crime, education, and road traffic. Withdrawing from the EU would presumably “free” Britain from at least some of these laws, leaving the country with the opportunity to replace them, should it so choose. This would not necessarily need to be done within two years. But Parliament would suddenly have the opportunity to revisit a huge swath of British domestic law.





In short, leaving the EU is easy — it will happen automatically in just two years if David Cameron gives the word. But filling the EU gap will require significant negotiation along numerous channels if Britain wants to be ready to stand alone in two years’ time. We should know tonight whether the country is getting on this particular roller coaster or whether it’s jumping off before it starts up the ramp.