Croatia will provide arguments to show that its decision not to accept the arbitration court ruling on the border dispute with Slovenia is not in violation of EU law, the letter that Foreign Ministry intends to send to Brussels by April 17 will say.

Croatia considers the June 2017 international arbitration ruling on a long-standing border dispute with Slovenia compromised because of a scandal during the process involving leaked tapes showing Slovenian government official inappropriately discussing the case with a court’s judge.

Although judges were later replaced, Croatia withdrew from the arbitration process in 2015, and considers the resulting ruling invalid. It asked for a new round of bilateral negotiations, which Slovenia rejects.

Slovenia, on the other hand, accepts the ruling in its entirety and interprets Croatia’s rejection of it a violation of EU and international law.

Ljubljana sent a letter to the European Commission (EC) asking its opinion on its stance, and has announced a lawsuit against Croatia at the Court of Justice of the European Union (CJEU) unless Croatia starts implementing the arbitration ruling. The EC asked Croatia to send in a reply by April 17.

Asked by the HINA state news agency whether the reply has already been sent, the Foreign Ministry said it would be done “on time”.

Slovenia launched the procedure with the EC in line with Article 259 of the Lisbon Treaty, which formally launched a three-month process during which both member EU member states involved in the dispute must send in written statements and hold a discussion at the EC in Brussels. The EC suggested May 2 as the date for the discussion.

The process may result in the EC stating its opinion on the matter. But regardless whether the EC decides to give its opinion, Slovenia can sue Croatia at the CJEU after the three months are up.