Former Philippine President Rodrigo Duterte’s daughter, Vice President Sara Duterte, travelled to the Netherlands on Wednesday following his arrest at the request of the International Criminal Court as part of its probe into his “war on drugs.”

Rodrigo Duterte, a maverick ex-mayor and former prosecutor who led the Philippines from 2016 to 2022, was flown to The Hague on Tuesday, hours after his arrest in Manila, marking the biggest step yet in the ICC’s probe into alleged crimes against humanity during an anti-drugs crackdown that killed thousands and drew condemnation around the world.

Duterte, 79, could become the first Asian former head of state to go on trial at the ICC.

His daughter Sara boarded a morning flight to Amsterdam, her office said in a statement, but it did not what she intended to do there or how long she plans to stay in the Netherlands.

Silvestre Bello, a former labour minister and one of the former president’s lawyers, said a legal team will meet to assess options and seek clarity on where Duterte will be taken and whether they would be granted access to him.

“First thing we will do is find out where exactly the former president will be brought so we know where we should go, because he will need legal assistance,” Bello said. “We will also discuss all possible legal remedies.”

Duterte is expected to arrive in the Netherlands on Wednesday. His youngest daughter, Veronica Duterte, plans to file a habeas corpus request with the Philippine Supreme Court to compel the government to bring him back, Salvador Panelo, his former chief legal counsel, said.

The war on drugs was the signature campaign platform that swept the mercurial Duterte to power in 2016. During his six years in office, 6,200 suspects were killed during anti-drug operations, by police count.

But activists say the real toll was far greater, with many thousands more slumland drug users gunned down in mysterious circumstances, some of whom were on community “watch lists” after they signed up for treatment.

Although Duterte unilaterally withdrew the Philippines from the ICC’s founding treaty in 2019 as it started looking into the drugs war, the court says it has jurisdiction to investigate alleged crimes that took place while a country was a member.

“Former President Duterte’s arrest and transfer to The Hague is a long-overdue victory against impunity that could bring victims and their families a step closer to justice,” said Bryony Lau, deputy Asia director at Human Rights Watch.

“This momentous event sends a message to human rights abusers everywhere that one day they could be held to account,” Lau added.