LONDON, - An arbitral tribunal's decision to allow the South China Sea case initiated by the Philippines against China to go ahead is not convincing, according to a leading international law expert at the University of Oxford.

In 2013, the Philippines unilaterally filed compulsory arbitration against China at the Permanent Court of Arbitration in The Hague with respect to the two sides' dispute in the South China Sea.

"For the most part, the tribunal hasn't answered satisfactorily with respect to why there is a dispute under the United Nations Convention on the Law of the Sea (UNCLOS), and also how these claims do not relate to sovereignty, and in my view they do (relate to sovereignty)," Antonios Tzanakopoulos, associate professor of public international law at the University of Oxford, said in a recent interview with Xinhua.

The dispute between the Philippines and China concerns sovereignty over maritime features in the South China Sea, but questions of sovereignty do not fall within the scope of UNCLOS, according to the expert, who had studied law in Athens, New York and Oxford and worked for the UN Office in Geneva.

"I think there are some very important questions, it hasn't answered fully. I don't think it has dealt with the issue of sovereignty very clearly," he said.

China made a declaration in 2006 in accordance with Article 298 of UNCLOS, making it clear that China would exclude disputes on maritime delimitation from compulsory arbitration.

Tzanakopoulos noted the tribunal "hasn't to a large extent answered how the claims put forward by the Philippines do not fall within the Chinese exceptions to the jurisdiction, because the convention allows every state to exclude some disputes from the jurisdiction of the relevant tribunals."

In April, Tzanakopoulos published a research paper in the Social Science Research Network, arguing that the tribunal's decision to give an award and allow the arbitration case to proceed is not convincing on many points.

"I read the award and then I was slightly uncomfortable with some of the things that it said. I had questions about how these are not related to sovereignty and so on and so forth," he said.

He added that "these international courts and tribunals don't actually have the power enforcing their decisions, so the best thing they can do is to give convincing answers to the disputes submitted by the states."

If a tribunal fails to do so, he warned, "there is a risk that the tribunal rendered a decision which fails to generally convince."

The scholar also pointed to "the indispensable third-party rule" in international jurisprudence, which could make the case inadmissible, but the tribunal "didn't answer satisfactorily and thoroughly" to the question.

He said the dispute is quintessentially a multilateral one involving many states, but the Philippines is "bilateralizing" this dispute.

"How can the tribunal essentially prejudge and decide claims of sovereignty at all, but even also claims of sovereignty of states not before it (i.e. states not involved in the case)? In the International Court of Justice (ICJ), this rule is called the Monetary Gold rule, or the indispensable third-party rule," he elaborated.

The expert noted that, in previous ICJ cases concerning indispensable third parties, the court "would refuse to exercise its jurisdiction and say the case is not admissible."

Tzanakopoulos went on saying that "the dispute settlement system in UNCLOS is not the best way to go about it, if this is done unilaterally by states starting disputes against other states on a bilateral level."