A general view shows the Lifford Bridge, where a customs unit was sited before the Good Friday Agreement, on the exact border between Strabane in Northern Ireland and Lifford in Ireland, August 2017.
Clodagh Kilcoyne / REUTERS

A new fight has been brewing over the consequences of Brexit for the border between Northern Ireland and the neighboring Republic of Ireland. Both British and EU negotiators have identified the border as one of the key political questions that have to be addressed early on in negotiations. It’s easy not to have a border between two states that are both part of the EU’s single market (the regulatory regime that allows easy trade across the EU) and customs union (the arrangement under which European states do not impose customs duties on each other and maintain a common customs policy toward all other countries).

Now, however, the United Kingdom is leaving the European Union, which means that Ireland’s northern border is about to become the land boundary dividing Europe and Britain. That has dangerous consequences. Since the signing of the Good Friday peace deal in 1998, Northern Ireland’

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  • HENRY FARRELL is Professor of Political Science and International Affairs at George Washington University’s Elliott School of International Affairs.
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