"No, I will only bring [up] the [arbitration case] face-to-face [with China]... because if you quarrel with them now, claim sovereignty, make noise here and there, they might not just even want to talk," declared Philippine President Rodrigo Duterte before his global diplomatic debut earlier this month.

The Filipino leader reassured his Chinese counterparts that he wouldn’t even mention Manila’s landmark legal victory against China during latest discussions of the South China Sea disputes at the Association of Southeast Asian Nations (ASEAN) summit.

This was no trivial matter. In its arbitration case, the Philippines managed to convince an international arbitral body, constituted under the aegis of the United Nations Convention on the Law of the Sea, to nullify the bulk of China’s "historic rights" claims over almost the entirety of the South China Sea, a global artery of trade.

Why is Rodrigo Duterte controversial?

Many observers expected the Philippines and other like-minded states to leverage the legal award in order to push back against Chinese island-construction activities, para-military patrols and military exercises in the disputed waters.

Yet, the Philippines’ newly minted leader, who has opted for bilateral negotiations with China, made it almost impossible for the United States and its allies to rally global pressure on China, at least in the meantime.

If anything, recent weeks have witnessed unprecedented verbal tussles between the Philippines and the US, two traditional allies, amid disagreements on human rights issues.

Meanwhile, much of Asia has demurred from any further diplomatic confrontation with Beijing, which seems to be back in the regional driving seat and relishing the US’ troubled alliances.

Strategic dissonance

Only a few months earlier, tens of millions of Filipinos were in ecstatic mode. Their country had just scored a moral victory at The Hague, when an arbitration body affirmed the Philippines’ sovereign rights in the South China Sea and censured Chinese aggressive manoeuvres and mind-boggling island-construction in contested areas.

The Permanent Court of Arbitration also made it clear that China’s notorious nine-dashed line claim is inconsistent with prevailing international law.

"Washington hoped that the Philippines’ arbitration case would provide a legal basis for deployment of greater diplomatic pressure as well as military assets to prevent Chinese domination of the world’s most important waterway."

Some legal experts encouraged Manila to file additional arbitration cases, suing China for inflicting massive ecological damage ($177bn) within the Philippines’ 200 nautical miles Exclusive Economic Zone.

Manila also had the option of calling upon major powers such as the US and Japan to conduct so-called freedom of navigation operations to challenge China’s excessive maritime claims in the area.

This way, the verdict from the court could be somehow enforced, even if an obstinate China refused to acknowledge its validity.

The Philippines could also go on an international diplomatic offensive, rallying global opinion in favour a rule-based resolution of the disputes.

If anything, it could also provide legal advice to other countries, which were contemplating a similar legal manoeuvre against China.

The newly inaugurated Duterte administration, however, preferred to simply set aside the arbitration case in favour of re-opening communication channels with China.

So it was left to a forlorn Obama to call for compliance with The Hague verdict during his participation at the ASEAN summit.

The situation was so bizarre that one leading Filipino magistrate suggested that the US president should rather be named as the defender of Philippine rights in the South China Sea.

Pivot in tatters

Over the past few years, the Obama administration, under its "pivot to Asia" strategy, gradually mobilised the region against Chinese maritime assertiveness in the South China Sea.

Washington hoped that the Philippines’ arbitration case would provide a legal basis for deployment of greater diplomatic pressure as well as military assets to prevent Chinese domination of the world’s most important waterway.

Chinese dredging vessels are purportedly seen in the waters around Mischief Reef in the disputed Spratly Islands in the South China Sea viewed in May 2015 [Reuters]

Yet, this "constrainment" strategy was predicated on constant cooperation and coordination between the US and its regional allies, especially frontline states such as the Philippines and Japan.

But as soon as it became clear that the Philippines itself was now unwilling to confront China over the South China Sea issue, however, almost all neighbouring countries shunned even mentioning the arbitration case at all.

Almost single-handedly, Duterte undermined the US’ strategy against China. To the astonishment of almost everyone, all of a sudden Manila and Washington are now at loggerheads.

The Obama administration has repeatedly criticised Manila’s ongoing "shock and awe"campaign against drugs. In response, Duterte has embarked on a series of expletive-ridden tirades against Washington, including an impromptu speech at the East Asia Summit, where he singled out the US’ colonial era crimes against Filipinos.

Duterte has described any criticism from the US as a violation of Philippine sovereignty. Most recently, Duterte has upped the ante by even threatening the expulsion of American Special Forces from the southern Philippine island of Mindanao. He has also called for cancellation of joint-patrolswith the US in the South China Sea, further complicating ongoing efforts at forging multilateral responses to Chinese assertiveness in the area.