How the U.K.’s Hold on Gibraltar Is Challenged by Brexit

The aftershocks of the U.K.’s exit from the European Union are still being felt in Gibraltar, the rocky outcrop at Spain’s southern tip that’s been British for three centuries. Its 2.35 billion-pound ($3.2 billion) services-based economy is dependent on the untrammeled flow of frontier workers and other visitors coming in from Spain -- the type of free movement that Brexit was meant to limit. Rules guiding border protocols are still in flux, even after the EU and the U.K. sealed their divorce.

The 6.8-square-kilometer enclave is a self-governing British overseas territory, like Bermuda or the Falklands Islands. As such, most of its 34,000 residents are British citizens, who voted almost unanimously in a 2002 referendum to remain under sole British sovereignty. At the same time, Gibraltar is physically part of Europe’s mainland, with deep ties to neighboring Spain -- which questions the legal basis of the U.K.’s claims to the territory ceded to Britain under the 1713 Treaty of Utrecht. In the 2016 Brexit referendum narrowly won by anti-EU forces, 96% of Gibraltarians voted in favor of remaining in the EU.