The United Kingdom's Supreme Court dismissed a challenge on Wednesday to the lawfulness of the controversial Northern Ireland Protocol, which governs post-Brexit trade between Northern Ireland and the rest of the UK.

The legal challenge, brought by pro-Brexit activists and former leaders of Northern Ireland's largest unionist parties, argued that the protocol, which left the province in the bloc's trading orbit, undermined its place in the United Kingdom (UK).

However, the Supreme Court unanimously dismissed the appeal, which has likewise been rejected by Northern Ireland's High Court and Court of Appeal.

It concluded the protocol neither breached the 1800 Acts of Union, nor the 1998 Northern Ireland Act, which followed a landmark peace deal that ended three decades of violence between Irish republicans and pro-British unionists.

Negotiated during Brexit talks, Northern Ireland Protocol came into effect in 2021. It is a special trading arrangement between the UK and the European Union (EU) that permits goods to be transported across the Irish land border without the need for checks after the UK left, as Northern Ireland, a part of the UK, has a land border with the Republic of Ireland, which is part of the EU. 

The protocol has disrupted trade between Northern Ireland and the rest of the UK and sparked anger in pro-British communities, leading to the challenge which was brought by former Democratic Unionist Party leader Arlene Foster, Traditional Unionist Voice leader Jim Allister and David Trimble, the late former Ulster Unionist Party leader among others.

The British government and the EU are involved in lengthy talks to hammer out a solution to the trade issues, but a deal so far remains elusive.

"A solution to the protocol was never going to be found in the courts, but the cases have served to highlight some of the reasons why unionists have uniformly rejected the protocol," DUP leader Jeffrey Donaldson said.

"The Protocol represents an existential threat to the future of Northern Ireland's place within the Union. The longer the Protocol remains, the more it will harm the union itself."

(With input from Reuters)

(Cover:  The Supreme Court of the United Kingdom in Parliament Square, central London, UK. /CFP)