The Democratic Unionist Party’s (DUP) bottom line has always been that any new Brexit arrangements should not separate Northern Ireland from the rest of the UK, economically or constitutionally.
Under the Stormont assembly’s cross-community voting rules, contentious measures require a majority of both unionists and nationalists in order to pass.
That means that the biggest parties – the DUP and Sinn Féin – in effect have a veto.
The DUP had hoped to secure an upfront Stormont vote to approve the new arrangements.
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But it’s understood that the current proposals would give Stormont a say four years after the end of the transition period – that would mean 2024.
A straightforward numerical majority would keep the special arrangements in place for another four years.
Alternatively, if the arrangements get cross-community consent – in other words, if they’re passed by most nationalists and most unionists – they would remain in place for eight years.
But a vote couldn’t happen if the assembly wasn’t operating.
Presently, it hasn’t sat for more than two and a half years, since Sinn Féin resigned from the power-sharing devolved government.
Shortly afterwards, an election left unionism without a numerical majority in the Stormont chamber for the first time in the history of Northern Ireland.