The protocol has been challenged by unionists, who say it breaches the Acts of Union and NI Act.
Image source, EPAThe Northern Ireland Protocol is lawful, the UK Supreme Court has ruled.
Part of the Brexit deal, the protocol creates a trade border between Northern Ireland and the rest of the UK.
It has been challenged by unionist politicians who say it breaches the Acts of Union and the Northern Ireland Act.
The court unanimously rejected their appeal on all grounds. It had previously been rejected by the High Court and Court of Appeal.
The protocol was agreed by the UK and EU in 2019 to ensure free movement of trade across the Irish land border after Brexit.
However, it means there are new checks and controls on goods entering Northern Ireland from Great Britain.
Image source, Aaron Chown/PA
The Supreme Court is the final court of appeal in the UK for civil cases.
It hears cases considered to be of the greatest public or constitutional importance affecting the whole population.
A five-judge panel, including Lord Reed, the president of the court, heard the case over two days in November.
In March 2022, the Court of Appeal found the Withdrawal Agreement Act, which includes the protocol, did conflict with the 1800 Acts of Union in respect of free trade between Britain and Northern Ireland.
However, the court added that the Withdrawal Agreement lawfully modified the Acts of Union.
The lady chief justice said the Acts of Union had not been repealed but one section, Article 6, now has to be read subject to the Withdrawal Agreement Act, which placed into law the arrangements for the protocol.