"However, the interpretation of UNCLOS in this case involves disputes among China and other neighboring countries, including the Philippines, on maritime delimitation and islands sovereignty and maritime demarcation in the South China Sea," Cai said, adding that the arbitral tribunal in this case has misinterpreted the meaning of optional exceptions made by China.

Cai said negotiations were a legal obligation under the DOC. The Declaration was signed by multilateral parties including China and other neighboring countries of the South China Sea and was repeatedly reiterated by leaders of the signatory countries in their intergovernmental engagements over a long period of time.

"In my view, the arbitral tribunal did not conduct adequate review or a reasonable judgment on the legal role of negotiation in this case," he said.

In Cai's opinion, consultation and negotiation can better facilitate the settlement of disputes, especially sensitive ones between countries.

"The arbitral tribunal on the South China Sea will not help solve the dispute," Cai said, "Such practice of the tribunal could worsen the dispute. The international community should focus more on dispute settlement and restoring order."

According to the Statute of International Court of Justice (ICJ), an important mission of ICJ is to settle disputes and restore order, Cai said. The tribunal of this case merely has a single-sided understanding of what an international dispute settlement body should do and its understanding on its own mission and nature is not in line with the statute of ICJ, he added.

He said legal loopholes sometimes exist in international law, part of which are "constructive ambiguities," which should have given some leeway with intent for various parties to reach agreements. However, the South China Sea arbitration represents an abuse of an incomplete system of international law, Cai said.