Britain and the European Union entered a high-stakes legal battle on Tuesday, as a three-day hearing at the Permanent Court of Arbitration began over post-Brexit fishing rights. The dispute centers on Britain's ban on sandeel fishing in its North Sea waters, which the EU claims violates the EU-UK Trade and Cooperation Agreement (TCA).

A tribunal composed of legal experts from France, New Zealand, and South Africa is set to rule on the case by late April. While the financial impact of the ban—estimated by Britain to result in a £45 million ($56.3 million) loss for EU fishing vessels—may be limited, the political ramifications are significant.

The tribunal's decision could either uphold the ban or rule it breaches the TCA, paving the way for EU retaliation if the ban is not lifted. Such an outcome could strain Britain's relations with the bloc, a sensitive issue as British Prime Minister Keir Starmer seeks to "reset" ties with the EU.

Prime Minister Starmer is expected to meet with EU leaders on Monday to discuss strengthening defense ties against Russia and addressing NATO-related military spending. Talks on other issues, such as a potential veterinary agreement to ease agricultural trade, are also on the horizon.

The British government defends the sandeel ban as necessary to protect marine ecosystems, citing scientific advice on the species' importance to the food chain of larger fish, marine mammals, and seabirds like puffins. Notably, British vessels do not fish for sandeels, which are predominantly caught by Danish fleets for use in animal feed and oil production.

The EU, however, argues that the ban is discriminatory and not based on the best available scientific evidence. It claims the prohibition unfairly restricts access to UK waters, in violation of the TCA.

As the legal proceedings unfold, the case highlights the lingering complexities of post-Brexit relations and the balancing act between environmental considerations and international trade commitments.