The EU alleged that the closure of Scottish and English waters to sandeel fishing breached the EU-UK Trade and Co-operation Agreement.

In a nearly 300-page ruling, the PCA has upheld the decision to close Scottish waters while identifying a procedural error in the decision to close English waters.

Mairi Gougeon, the Scottish government’s cabinet secretary for rural affairs, land reform and islands, said: “This is an extremely positive ruling, especially with respect to the closure in Scottish waters where all claims have been successfully defended. As such, the prohibition of sandeel fishing in Scottish waters will remain in place.

“Protecting our marine ecosystem is vital to Scotland’s environment, and to the people and communities who rely on it. The ruling reaffirms the appropriateness of the actions we took last year to do just that.

“The prohibition of sandeel fishing in Scottish waters has the potential to provide long term sustainability and resilience to the marine ecosystem, as well as bringing about potential benefits to sandeel, seabirds, marine mammals and other fish species.

“This outcome, with respect to Scottish waters, reflects the robust, evidence-based and transparent public consultation and processes that the Scottish government has in place.”

The UK government has said it will address the issues relating to the English decision without reversing the ban.

A spokesperson said: “We welcome the clarity provided by this decision, and we will undertake a process in good faith to bring the UK into compliance on the specific issues raised by the tribunal. 

“The ruling does not mean the UK is legally obliged to reverse the closure of English waters, and the decision to close Scottish waters was fully upheld. 

“We remain committed to protecting our seabirds and the wider marine environment, in accordance with our commitments to the TCA and other international agreements.

“Disputes and the use of resolution mechanisms are a normal part of a mature relationship with international partners. We will continue to act in the national interest as we work towards a strong and lasting partnership with our European neighbours.”