NORTHERN Ireland First Minister Arlene Foster contended that pro-EU ruling by a Belfast court is incompatible with the UK's constitution under the Acts of Union.

This after a Belfast judge quashed a lawsuit challenging the Northern Ireland Brexit protocol in a boost for UK and European Union negotiators hours before they were to announce checks on goods across the Irish Sea.

Judge Adrian Colton ruled that post-Brexit trading agreements concerning Northern Ireland are lawful even though they conflict with the 1800 Acts of Union.

The protocol created border checks in the Irish Sea to resolve disputes between the UK and EU over goods entering the Republic of Ireland.

This was a method post Brexit to avoid checks on the land border between British Northern Ireland and the Republic to avoid violence between Irish Republican and Ulster Loyalist paramilitaries.

"The key finding in today's court ruling that the protocol has repealed a key plank of the Acts of Union is a wakeup call to every unionist," Jim Allister, a loyalist politician in Northern Ireland and lead claimant in the case,. "It is now confirmed the protocol is dismantling the Union."

An agreement between the EU and UK is expected to extend the grace period for post-Brexit trading rules in Northern Ireland. Under current arrangements the sale of chilled meats and fresh sausages into Northern Ireland from the rest of the UK is due to be banned at the end of June.