If Britain leaves the EU, what would happen to Ireland

“We’ve been in the sweetspot for the economy, but the Brexit vote is bringing lots of unwelcome uncertainty,” says Fergal O’Brien, chief economist at the Irish Business and Employers’ Confederation (IBEC). “Our major corporations invest more in Britain than any other nation to sell our goods there, and it’s the first export market our small companies enter. Both of those flows could be in jeopardy if Britain leaves the EU.”

A “leave” vote by the U.K. could reverse much of the progress from one of the landmark political achievements of the close of the last century, the Good Friday peace accord of 1998.

That historic pact effectively ended the bloody fighting between the Catholic nationalists and Protestant unionists, who were defended by British troops, allowing workers and goods to flow across the once-heavily barricaded border between the two Irelands. A hallmark of the accord was the stipulation that crossing between the North and the South would always remain open to British and Irish workers moving in both directions.

But if the “leave” vote prevails, Britain might close the jagged, 300 mile frontier to control immigration from inside and outside the EU, a major goal of the “leave” contingent. The U.K. could even ban the 30,000 Irish workers who commute daily to jobs in such cities as Ulster and Belfast, who would no longer have the automatic right to work in Britain that they now enjoy under EU law. The delays for custom checks would also raise the cost of transporting everything from milk to diesel fuel across the border, hurting trade.