President Borut Pahor said the European Commission's ignoring the opinion of its own Legal Service due to political reasons was a bad message for potential future border agreements in the Western Balkans.
He said the Commission had missed an opportunity by failing to give an ear to its Legal Service and by failing to say that bilateral agreements that have been ratified and that have set the border through the arbitration tribunal's award must be respected.
"That's the essence of the opinion that the Commission failed to take into account for political reasons," Pahor said on the sidelines of a ceremony marking Primorska Reunification Day in Komen.
In a written response, Foreign Minister Miro Cerar said that the document published by Der Speigel reaffirmed his assessment that the European Commission failed to do its job as a guardian of EU treaties.
"It all confirms that there's no other way but for both countries to set out to implement the award," Cerar said, adding that several months ago, when he still served as prime minister, Slovenia proposed forming a bilateral demarcation commission to make the life of people along the border easier.
"A second option is to wait for another court to make its judgement. If not before, it will be clear then that Croatia's failing to implement the award is not only a violation of international law, but also of EU law. Croatia will be forced to set about implementation then," Cerar said.
"In the spirit of good neighbourly relations and respect for common European principles, we express the hope that now at last Croatia will now stop with infringements against EU law, in particular at sea, and set out to implement the arbitration award," Cerar wrote.
Prime Minister Marjan Šarec responded by saying that the rule of law must be respected, something that he said was also ascertained by the European Commission's Legal Service, but that the Commission obviously decided otherwise.
He said the European Commission was a political body rather than a court so it had a discretion to decide whether it would take legal opinions into consideration or not. "It has decided to stay neutral, which didn't make us happy then and doesn't make us happy now because it is a wrong message."
"We must insist on the rule of law," Šarec said on the sidelines of the ceremony in Komen, adding that the arbitration award must be implemented, even though "it wasn't as favourable for Slovenia as some may have thought".
Speaker Dejan Židan took his criticism further by saying that Commission President Jean-Claude Juncker threatened the foundations of the EU through his politically-motivated actions.
Židan, the leader of the Social Democrats, noted that Slovenia's current and previous governments are not right-wing and that the European Commission is controlled by the centre-right European People's Party.
"The European Union is founded on respect for the law, which means that legal postulates and international judgements must be respected in full, because this guarantees some security to small nations," Židan said in Komen.
He said that Slovenia had sensed all along that the law was on its side. "It was due to political considerations, which may jeopardise the foundations of the European Union, that Juncker acted in a wrong way, so its' right he is leaving."
Židan expressed the hope that the upcoming elections to the European Parliament would be won by moderate people to whom Europe mattered and who were aware there could not be one without law.
The German weekly magazine released an eight-page legal opinion, dated 14 May, 2018, which the Legal Service drew up for the Commission before the three-month period expired for a response to Slovenia's proposal under Article 259 of the Treaty on EU.
In the document, the Legal Service proposed that the Commission adopt the "reasoned opinion" and to take up the case against Croatia in accordance with the mentioned article.
However, Der Spiegel said that Juncker was ignoring his own legal staff's advice, suggesting that this was to help Croatian PM Andrej Plenković, who is a member of the same political party.
More details on Der Spiegel Revelations
The STA reports that the German weekly magazine released the eight-page legal opinion, dated 14 May, 2018, which the Legal Service drew up for the Commission before the three-month period expired for a response to Slovenia's proposal under Article 259 of the Treaty on European Union (TEU).
In the document, the Legal Service proposed that the Commission adopt the "reasoned opinion" and to take over the case against Croatia in accordance with the mentioned article. The letter was addressed to the head of the cabinet of the European Commission, and signed by Karen Banks.
Summing up the Slovenia-Croatia border arbitration dispute, the Legal Service's opinion says that Slovenia's complaint is, in essence, that Croatia, by refusing to recognise the arbitration award, prevents Slovenia from fulfilling its obligations and enjoying its rights under EU law.
The Legal Service also noted that the arbitration tribunal in 2016 rejected Croatia's claims that the arbitration process was compromised and that the arbitration agreement was no longer valid.
Thus the only relevant question for the EU is whether it should respect the decision of the international arbitration tribunal and take it into consideration in the application and interpretations of questions of EU law.
The Legal Service notes that the obligation to respect international law must include respect for legal principles such as "pacta sunt servanda" (agreements must be kept) and "res judicata" (respecting a matter already judged), that is including treaties such as the arbitration agreement and the arbitration award.
"In this respect the fact that implementing measures may still have to be taken, as argued by Croatia, cannot mean that it would be possible to disregard the final award and the provisions of the Arbitration Agreement.
"The possible implementation would therefore only concern arrangements on the material demarcation of the border where this is needed (mainly on land) and the adjustment of internal legislation and regulation. In the marine areas the lines have been precisely determined by the award and this aspect would normally not even require any further arrangements on demarcation.
"In the light of the above, and without making any judgements of its own, the Commission must just observe that there is an arbitration agreement which has not been validly terminated and that there has been final determination of the borders between Slovenia and Croatia.
"Therefore the outcome of the arbitration procedure must be respected by the EU, and provisions of EU law must be interpreted in the light of it," the Legal Service's opinion reads.
The opinion also sums up and endorses Slovenia's claims of Croatia's infringements of the general duty of loyal cooperation under Article 4 of TEU, specific duties under the Common Fisheries Policy, specific duties under the Schengen Code and specific duties under Maritime Special Planning Directive.
According to Der Spiegel, the European commissioners responsible for the issue have yet to see the legal opinion. The weekly says that Commission President Jean-Claude Juncker is ignoring his own legal staff's advice, wondering whether this is to help Croatian PM Andrej Plenković, who is a member of the same political party.
The magazine notes that Juncker himself argued that the border dispute between Slovenia and Croatia "must be resolved" when he raised the matter in the European Parliament in February. After all, he said, it is not just a problem for the two EU members, but "a European problem".
"In a strange twist ... it's now the European Commission chief himself who is delaying a solution. The Commission had several opportunities to act as an arbitrator in the conflict, but Juncker decided to stay out of it, even though his own staff has no doubt that Slovenia's position is largely correct in the matter," writes Der Spiegel's Brussels correspondent Peter Müller.
Asked for comment, the Slovenian Foreign Ministry told the STA that it was not commenting on media reports, but that "Slovenia is committed to respecting the rule of law and decisions of international courts. We believe the European Commission shares our view."
Dominika Švarc Pipan, an international law expert who has recently been appointed one of two state secretaries at the Ministry of Justice, tweeted: "No wonder the Commission wouldn't make the opinion public or send it to Slovenia. It'll now be really hard to justify silence or pretend ignorance any longer."
The European Commission would not comment on Der Spiegel's report. In response to a query by the STA, the Commission said it was not commenting on the many internal documents that may be circulating in the Commission.