The Commission is taking the U.K. to the Court of Justice of the EU (ECJ). Although Britain ceased to be bound by EU law post-Brexit, certain matters contained in its withdrawal deal fall under the European court’s jurisdiction ― much to the annoyance of Britain’s pro-Brexit politicians.

In a statement, the Commission blasted the U.K.’s “shortcomings” in implementing the terms of the treaty, “which continue to affect EU citizens.”

“After carefully assessing the replies of the United Kingdom, the Commission maintains that several elements of the grievances remain unaddressed, including on the rights of workers and the rights of extended family members,” the Commission added.

The violations happened at the end of 2020, the Commission said.

A U.K. government spokesperson said the cases related to “issues from when the U.K. was an EU member state and during the transition period,” which was in 2020 before the signing of a trade deal between the two sides.

“We remain focused on working to reset our relationship with the EU and to make Brexit work for the British people,” the spokesperson said.

Politicians from the Conservative Party, which was in government at the time of the Brexit negotiations, were quick to seize on the dispute.

“The EU’s enthusiasm to continue to take proceedings against us in the ECJ should be a warning to Keir Starmer as he tries to edge us back under its jurisdiction in more areas and extend mobility rights for EU citizens,” Shadow Foreign Secretary Priti Patel said. “I hope the government will strongly defend this claim.”