Slovenia on Monday warned fellow EU member Croatia that failure to implement the Piran ruling will amount to a breach of the EU’s rule of law, EurActiv.com reports.

The 11th edition of the Bled Strategic Forum opened yesterday with speeches by the country’s president, Borut Pahor, its prime minister, Miro Cerar, and foreign minister, Karl Erjavec. The Forum is increasingly building a reputation as a mini-Davos, opening the political season at the start of September.

All three speakers made references to the “rule of law” in the EU, which may have mistakenly been understood as criticism of Poland, the only EU country under the so-called “Rule of Law mechanism”.

The unprecedented move by the European Commission against Poland, which started in January 2016 and has not concluded yet, is the first step in a potentially-punitive process aimed at buttressing democracy and rights in the 28 EU states.

But Slovenia’s highest ranking officials were actually referring to neighbouring Croatia with whom Ljubljana has a long-standing dispute over territorial waters in the bay of Piran.

Candidate countries are usually requested to solve territorial disputes with neighbours before entering the EU, so as to avoid making their bilateral issues an EU problem.

The dispute over the contested northern Adriatic waters and a sliver of land between the two countries dates back to the 1991 break-up of Yugoslavia. Slovenia, which joined the EU in 2004, blocked Croatia’s accession talks in 2008 because of the border issue.

The two sides eventually agreed to hand the matter over to an international tribunal in The Hague and the agreement allowed Croatia to resume membership talks and join the bloc in 2013. The deal was included in Croatia’s accession agreement in order to stop Slovenia vetoing its membership.

The tribunal announced its ruling on 29 June 2017. But Zagreb confirmed on the same day that it will not respect the ruling.

Croatia says the result is null-and-void because the arbitration process was tainted after it emerged in 2015 that a Slovenian official had discussed the case with a member of the arbitration committee. Ljubljana does not contest this charge but still insists that Croatia must stick to the terms of the deal.

A high ranking Slovenian diplomat told a small group of journalists that Croatia should not be able to enter the Schengen area because its rejection of the court ruling means it is unclear where the Schengen border lies.

Iztok Mirošič, State Secretary in Slovenia’s foreign ministry, said it would be “very funny” for a country to enter the Schengen agreement “when we don’t know which border is valid – the border determined by international ruling, or the border that Croatia says is its border”.

“Rule of law means also respect of international law,” he said, adding that his country too was not satisfied with the arbitration agreement, which he called “balanced” and neither in Slovenia nor Croatia’s favour.

However, he stopped short from suggesting Slovenia was putting its veto on Croatia’s Schengen bid, a decision which requires unanimity. “I didn’t say that”, he replied when asked by EURACTIV.com.

He added that the six-month period for implementing the court ruling was only just beginning and that his country wanted to do this with Croatia.

“We are prepared to wait for Croatia, to think about it, to think about international law,” he said.

The decision will set a precedent for the Western Balkans, Mirošič added, saying the process was intended from the beginning to be an example of how similar problems should be solved in the future.

The diplomat acknowledged that Slovenian actors “made mistakes” during the process. But this, according to the court, did not give Croatia the right to walk away from the process.

“We expect that Croatia will take into respect the broader regional environment,” he repeated.

The Slovenian diplomat added that Commission First Vice President Frans Timmermans, who was present in Bled, had offered his services for a possible mediation.

“I don’t know if this is suitable in present times, while we are in preparation for the six-month period of the implementation [of the ruling], but count on the Commission to do everything possible for the implementation of the international obligations of the member country,” he said.

The College of Commissioners discussed the issue at its 19 July meeting. According to the minutes of the meeting, the EU has jurisdiction over the court ruling, which seems to comfort Ljubljana.