Option No. 4:
An exit in name only

Article 50 gives an exiting country two years to negotiate terms for its relationship with the union, on issues like trade and migration.

What if Britain struck a series of deals that largely preserved the status quo, only without formal European Union membership?

This, too, seems to be something Mr. Johnson is pondering. In an op-ed in The Telegraph on Sunday, he promised that Britain would maintain free trade and free movement deals with Europe.

As Rafael Behr, a columnist for The Guardian, joked on Twitter: “Otherwise known as ‘membership of the European Union.’ ”

One model is Norway, which is not a European Union member but subscribes to its common market and open borders.