Croatia has refused to recognise a ruling by an international tribunal in the Netherlands, which, on Thursday (29 June) delivered a verdict on an outstanding sea and land border dispute with Slovenia.

"We do not consider ourselves bound by this decision because it was irreparably contaminated and compromised by the actions of the Slovenian side," Croatia's ambassador to the EU, Mato Skrabalo, told EUobserver.

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The nearly 400 page judgment appears to have handed Slovenia the vast majority of the Bay of Piran and set up a special corridor to give the country access to the high seas via Croatian waters. Slovenia has a 46 kilometre coastline, compared to Croatia's 1,700.

The court awarded some parts of the land border disputes to Croatia, and others to Slovenia.

But Croatia says the Hague-based Permanent Court of Arbitration was no longer valid, following disclosures in 2015 that a Slovenian official had inside contacts with the court's Slovenian arbitrator. The arbitrator resigned the day after.

The two sides had initially agreed to the arbitration in 2009 as part of a deal that lifted Slovenia's veto against Croatia's membership of the European Union in 2013.

But revelations about the insider triggered the Croatian parliament in 2015 to unanimously terminate the arbitration agreement. The five-member tribunal was then put on temporary hold until it decided to continue the deliberations in mid-2016.

On Thursday, Croatia refused to accept a copy of the tribunal's decision and maintained that the issue must be resolved on a bilateral basis.

"We believe that this issue of border limitation between Croatia and Slovenia is still open," said Skrabalo.

Skrabalo said that while the border areas remained in dispute, Slovenia still had unimpeded access to and from Slovenian ports.

"There is nothing that would impede access to their ports," he said, noting that his country wanted to keep friendly relations.

Dispute not over, yet

Croatia's intransigence is likely to stoke tensions between the two sides, in a European Union that prides itself on decades of uninterrupted peace.

However, neither side is likely to take any action, aside from diplomatic ones, to provoke the other.

Slovenia's prime minister, Miro Cerar, said on Thursday that his country would do nothing that "might serve to exacerbate relations between our two countries and their citizens."

Instead, Slovenia is hoping the European Commission will pressure Croatia into accepting and recognising the ruling, noting that the ruling must be implemented within six months.

But the commission on Thursday said that it needs time to study the ruling, also called an award, before it makes any comment sometime next week.

Cerar emphasised that the court's decision is final and legally binding on both Slovenia and Croatia.

"Slovenia and Croatia have attempted to resolve the border issue ever since independence, but without success," he said.

He noted the tribunal had awarded three quarters of the Bay of Piran to Slovenia.

He also said that it set up a special access area (or “junction area”), which is 2.5 nautical miles wide, inside Croatian territorial waters. This gives Slovenia the right of transit and navigation for all aircraft and vessels travelling to and from the country.

"The Republic of Croatia may not take from us or limit this access," he said.