France, July 15 -- Several hundred people gathered for the occasion, waving Spanish flags, as Gibraltar's Chief Minister, Fabian Picardo, declared: "Europe is back."

An AFP journalist at the frontier reported that several dozen people and vehicles crossed the border from Spain for the first time without undergoing customs checks, just minutes after midnight.

Gibraltar, a self-governing British territory at the southernmost tip of the Iberian peninsula, is home to only around 40,000 people, but relies on some 15,500 workers who cross from Spain every day.

During rush hours, long queues have often formed at the land border as documents are checked, particularly during periods of tension between Britain and Spain, which claims sovereignty...