For the first time in history, the International Criminal Court (ICC) has opened a preliminary probe against an incumbent Southeast Asian leader.

The Philippine President Rodrigo Duterte, who has waged a bloody campaign against suspected drug dealers, stands accused of committing crimes against humanity.

The Netherlands-based body is currently conducting "preliminary examination" of its jurisdiction to oversee the case. Some legal experts see this as the first step towards a full prosecution of the controversial Filipino leader, who has lashed out at the international tribunal as "hypocritical" and "useless".

The announcement has already re-energised opponents of Duterte and his drug war, which has reportedly led to the death of thousands of extrajudicial killings across the country. Many are hoping that the government will eventually reconsider its anti-drug campaign and hold erring officials to account.

The shadow of prosecution for crimes against humanity is also likely to cloud relations between Duterte and his international partners, especially in the West. Countries such as Canada are already reconsidering their sales of advanced military equipment to the Philippines.

Above all, victims of extrajudicial killings are hoping for a measure of justice and reparations for their suffering and loss.

An exclusive club

In the past, the Philippine government often warned of withdrawing from the Rome Statute, which undergirds states' obligations under the ICC. But the move would have been unable to stop the proceedings if the ICC were to embark on the full prosecution of Duterte on charges of crimes against humanity.

Duterte has been accused of initiating a systematic campaign of state-sponsored violence, leading to suffering and death on a large-scale. Human Rights Watch has welcomed a potential ICC prosecution as a justified response to what it claims are "invariably found unlawful executions by police or agents of the police typically acting as death squads" under the Philippine government.

Since its establishment in 2002, the court has overseen the prosecution of nine high-profile cases out of as many as 12,000 complaints. Most of the indictments have come against African leaders from countries such as Sudan, Central African Republic, Ivory Coast, Kenya, Mali, and Uganda.

For this reason, the court at The Hague has been accused of selective justice, failing to prosecute leaders of powerful nations, especially from the West, for committing mass atrocities on an even larger scale.

Authoritarian countries such as Russia, Burundi and The Gambia have withdrawn from the ICC in recent years, though a local court blocked a similar decision by the Jacob Zuma government in South Africa for violating the constitution.

The Filipino leader, however, has remained defiant. "The president welcomes the preliminary examination because he is sick and tired of being accused of the commission of crimes against humanity," said Presidential Spokesman Harry Roque in a media briefing. "If need be, [Duterte] will argue his case personally and face the ICC."

In recent months, Duterte has also re-activated the drug war campaign, which he suspended late last year amid massive public backlash over the death of several teenagers at the hands of law enforcers. Proud and peevish, the popular Filipino leader determined to dig in and not succumb to external pressure.

The political fallout

Based on the principle of complementarity in international law, the ICC can step in once there is sufficient evidence that local courts and institutions are unable or unwilling to ensure justice vis-a-vis mass atrocities.

Duterte's opponents claim that local courts and institutions of accountability are either under the president's control or face tremendous political pressure from the government. In recent months, the Filipino leader has threatened to impeach the heads of the Ombudsman Office and Supreme Court, who have stood up to Duterte and are seen as few remaining bastions of independence.

The legislature, meanwhile, is stacked with Duterte's super-majority coalition. Nonetheless, the Commission on Human Rights, which is headed by critics of the president, has expressed its willingness to assist any possible investigation by the ICC about Duterte's alleged crimes under drug war.

The court, however, can't prosecute cases that occurred prior to the Philippines' accession to the Rome Statute in 2011. According to the ICC chief prosecutor Fatou Bensouda, her office will analyse alleged crimes committed since Duterte's ascension to the presidency in July 2016.

While it's too early to predict a full trial of high-level officials in Philippine government, the political landscape is beginning to shift.

Amid re-invigorated international scrutiny of Duterte's human rights record, Western nations have begun to reconsider their relations with Manila. The government of Canada began revisiting its planned sales of military equipment to the Philippines, while the US Congress has refused to authorise any Foreign Military Financing (FMF) to the Southeast Asian country.

Irked by the criticisms, Duterte has called for the cancellation of all military purchases from Western nations. He may seek closer defence and strategic cooperation with China and Russia instead. In a surreal turn of events, the Philippines, long a bastion of democracy and human rights in Asia, is increasingly finding itself in a nauseously exclusive club of rogue nations. Justice for the victims of the drug war, however, is far from assured.

The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial stance.