Customary law does not define ICC jurisdiction

The jurisdiction of the International Criminal Court (ICC) is dictated by its founding treaty, the Rome Statute, not by customary international law. 

Customary international law refers to regulations that are not set by agreements or treaties. It arises from state practice and beliefs about what constitutes violations of the law.

During a press briefing on March 27 however, reelectionist Sen. Imee Marcos claimed that while International Humanitarian Law (IHL) is customary law, the ICC’s jurisdiction is not:

IHL is international customary law, but the jurisdiction of ICC cannot be considered customary under IHL.

IHL, which refers to the set of rules on war crimes committed during times of international armed conflict, has no connection to the regulation of the ICC’s jurisdiction. 

Although IHL is considered customary under international law, it is not international law that dictates the jurisdiction of the ICC. 

Article 5 of the Rome Statute states that the court’s jurisdiction covers “the most serious crimes of concern to the international community as a whole.” 

Marcos also argued that the ICC’s jurisdiction applies only to states party to the Rome Statute.

While the Philippines withdrew from the Rome Statute effective 2019, the ICC retains jurisdiction over crimes committed while the country was a member. 

A 2021 ICC ruling affirmed its authority over alleged crimes that occurred between 2011 and 2019 when the Philippines was still a state party.

Marcos further said the rights of former President Rodrigo Duterte were violated under Philippine law when he was turned over to the ICC. The government cited Republic Act 9851, or the "Philippine Act on Crimes Against International Humanitarian Law, Genocide, and Other Crimes Against Humanity," as legal basis for his transfer.

Despite its name, R A 9851 does not exclusively cover war crimes. 

This case is also not the first time that crimes against humanity will be tried by an international court.

The 1945 Nuremberg Trials, conducted by the International Military Tribunal, established that crimes against humanity are violations of international law.

A United Nations memorandum on the trial states that crimes against humanity “may then be said to be of international concern…without abandoning the principle that treatment of nationals is normally a matter of domestic jurisdiction.”

Likewise, in 1999, the International Criminal Tribunal for the Former Yugoslavia, in Prosecutor v. Dusko Tadic, upheld its jurisdiction over crimes against humanity based on  a United Nations resolution.

In short, the ICC’s authority is not grounded in customary international law but in the Rome Statute. Duterte’s case remains within its jurisdiction because the alleged crimes occurred when the Philippines was still covered by the Rome Statute.

Marcos’ press briefing came amid her Senate foreign relations committee’s investigation of Duterte’s transfer to The Hague. 

The ICC issued a warrant of arrest for Duterte on March 7. The former president was arrested on March 11 and turned over to the custody of the ICC. (KB)