MANILA — President Ferdinand Marcos, Jr.'s decision for the Philippines to refrain from rejoining the International Criminal Court (ICC) is "an issue of sovereignty", Malacañang said on Tuesday.

Press Secretary Trixie Cruz-Angeles said the Philippines was investigating the killings under the war on drugs of former President Rodrigo Duterte, which is also the subject of a suspended ICC inquiry that its prosecutor wanted to resume.

"Ang hindi natin pagbabalik sa ICC ay isyu ng soberanya," Cruz-Angeles said, after some rights group called the decision to stay out of the ICC a "terrible mistake."

"Sa kasalukuyan, iniimbestigahan naman po ang mga reklamo ukol dun sa mga namamatay during the drug war kung kayat hindi na nangangailangan pang tumugon sa ICC o bumalik ang ating bansa sa Rome Statute," she said in a press briefing.

(Our decision no to return to the ICC is an issue of sovereignty. The complaints on those who died during the drug war are being investigated, so we need not respond to the ICC or return to the Rome Statute.)

In March 2018, then President Rodrigo Duterte canceled the Philippines' membership in the Rome Statute, ICC's founding treaty, after it launched a preliminary probe into his narcotics crackdown.

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Kristina Conti, a lawyer representing drug war victims, said there was "no investigation in the Philippines which will entail the same questions the ICC is pursuing."

"We are looking at an investigation into who did what and who did not do what they should do... The investigation should and would point out the accountabilities of those who had to do something or should have done something but did not," Conti told ANC.

Philippine Coalition for the International Criminal Court co-chairperson Aurora Parong said staying out of the ICC would deny justice to Filipinos should processes in the country "fail" them.

"When President Marcos said that he will not rejoin the ICC, he is depriving people of a court of last resort for those serious crimes," she said in an ANC interview.

"And even our problem at the West Philippine Sea because crime of aggression is included and so that's a possible area for accountability," added Parong, referring to China's incursions into a portion of the South China Sea, which is within the Philippine exclusive economic zone.

Video from PTV

Cruz-Angeles said that while Malacañang "understood" the concerns of drug war victims, "Bukas po ang ating mga hukuman at ang proseso ng hustisya para sa kanilang hinaing."

(Our courts and judicial processes are open for their grievances.)

"Bahagi po ng ating proseso ang mabilis na paglilitis lalung-lalo na doon sa mga kriminal na kaso, so hindi na kailangan magbigay ng direktiba ang Pangulo, bahagi na po yun ng sistema ng hustiya," she added.

(Swift trial, especially for criminal cases, is part of our process, so our President need not give a directive. That's already party of the justice system.)

ICC judges authorized a full investigation into the anti-narcotics campaign last September, saying it resembled an illegitimate and systematic attack on civilians. It suspended the probe 2 months later, after Manila said it was looking into the alleged crimes itself.

Last June, ICC prosecutor Karim Khan said that the request to defer the probe was unjustified and that it should restart "as quickly as possible".

But Marcos said on Monday, "The Philippines has no intention of rejoining the ICC."

• Marcos meets with top legal officials on ICC probe

Marcos won the elections with the help of an alliance with his predecessor's daughter, Vice President Sara Duterte.

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The previous Duterte administration, under pressure from the UN Human Rights Council and the ICC, has examined several hundred cases of drug operations that led to deaths.

Charges have been filed in a handful of cases. Only 3 police have been convicted for slaying a drug suspect.

The ICC has invited the Philippines "to offer observations" on Khan's request to resume the probe, the presidential communications office said.

Manila has until Sept. 8 to respond.

At least of 6,000 people have been killed during anti-illegal drugs operations since July 2016, data from the Philippine Drug Enforcement Agency (PDEA) showed.

The elder Duterte had denied there were extrajudicial killings under the narcotics crackdown.

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— With a report from Agence France-Presse