In light of recent revelations that the EU Commission had ignored the opinion of its own Legal Service that Croatia's refusal to accept the arbitration reward constituted a violation of EU law, Cerar said the Commission had discretion in making such decisions.
Read more about Der Spiegel’s shock report on the European Commission ignoring legal advice favouring Slovenia on the border here
However, he pointed out, Slovenia could not agree with such a stance and needed to "raise its voice" against it, as all member states should raise their voice to protect European values.
Noting that the Commission had advocated the need to implement the arbitration award, Cerar said it only recently started "improperly politicising" the issue.
In this case, making the implementation of the award a political issue is harmful for the future of the Commission and the EU, Cerar stressed and added that failure to respect the arbitration set a bad example for Western Balkan countries.
"How can the EU convincingly enforce the argument that they must respect the rule of law if it allows a key country in the region, which is already an EU member states, to clearly violate this and several other legal commitments," the foreign minister said.
Cerar, who was the prime minister when the arbitration award was pronounced last year, said Slovenia wanted to take the dispute from the political to the legal level by suing Croatia at the European Court of Justice, because a political deal with Croatia was impossible.
The opinion of the European Commission's Legal Service is important because "it further reinforces our conviction that the arguments in our lawsuit are justified".
It is up to the EU court to decide whether to take the opinion into consideration, but Cerar believes the judges will have enough facts on the table to decide that Croatia is violating EU law. "This will constitute additional pressure on the neighbour to implement the arbitration award."
On the other hand, the new foreign minister has been unpleasantly surprised by a lack of unity in support of the lawsuit in Slovenia, as some members of the opposition Democrats (SDS) and New Slovenia (NSi) want to downplay its importance at the expense of Slovenia's interests.
Meanwhile, Cerar indicated that Prime Minister Marjan Šarec should accept the invitation of Croatian counterpart Andrej Plenković to visit Zagreb, but he also said that Šarec should continue the course set out by the previous government regarding the arbitration.
"We have good relations with Croatia at many levels, from business to culture, and we must not disregard them because of certain contentious issues such as arbitration and LB," he added in reference to the issue of lawsuits in Croatia stemming from Yugoslav times and related to the defunct LB bank.
Cerar will hold talks with Šarec in the coming weeks to discuss Slovenia's foreign policy, above all Slovenia's forthcoming presidency of the Council of the EU as well as other matters such as Brexit and relations with neighbouring countries.
Slovenia already launched preparations for the 2021 presidency during the previous government's term, "but at the moment we're far from ready and we'll have to give it an absolute priority".
"We're short of staff, and it will cost the country, we believe around EUR 70m. I'm speaking about essentials, not luxury things, because Slovenia must be ready in terms of logistics and staffing. The presidency is a great opportunity and responsibility at the same time."
Overall, Cerar believes Slovenia must maintain an active role in the EU: "We must voice our demands and initiatives clearly ... and defy all radicalisms, both left and right, that want to harm the European idea and the people."
Commitment to European values was also one of the reasons Cerar picked a non-diplomat, former chief of the general staff Dobran Božič, as a state secretary at his ministry.
"I picked Božič because he has international experience and connections around the world ... At the same time he is a very good organiser and committed to the same European values as I am."
"But I must stress that we will not break off or limit good relations with anybody. On the contrary, we will upgrade relations where they are good. In certain areas - especially in relations with the US - we must establish better ties, cooperation, because the US is our strategic ally.
"I understand that the US president is implementing policies that worry Europe, especially with indications of trade wars. Nevertheless, we are allies and the US is an extremely important factor at the global level."
However, good relations with the US will not come at the expense of any other country: "I don't want to impede relations with Russia in any way."
Cerar's first trip abroad will be to New York for the UN General Assembly, where he expects to hold six to seven bilateral meetings, meet his EU counterparts, and attend a NATO dinner, to which he has been invited by US Secretary of State Mike Pompeo.
He then plans to attend a meeting of the EU foreign ministers, while he is still putting together a plan for bilateral visits.
"Certainly I will first try to meet foreign ministers of key European countries, and in particular my counterparts from neighbouring countries," he added.
