How four different customs union options led to the Irish border backstop compromise

EU-UK

customs union

Red line for May

No need for Irish

border checks

 

EU-NI

customs union

Red line for DUP

No need for Irish

border checks, but checks needed on goods moving between NI and the UK

UK-NI customs union (soft border)

Red line for Brussels

Lack of checks on Irish border leaves a back door to the EU single market

UK-NI customs union (hard border)

Red line for Dublin

Hard border to preserve integrity of EU single market contravenes Good Friday agreement

EU-UK

customs union

Red line for May

No need for Irish

border checks

 

EU-NI

customs union

Red line for DUP

No need for Irish

border checks, but checks needed on goods moving between NI and the UK

UK-NI customs union (soft border)

Red line for Brussels

Lack of checks on Irish border leaves a back door to the EU single market

 

UK-NI customs union (hard border)

Red line for Dublin

Hard border to preserve integrity of EU single market contravenes Good Friday agreement