French judges have ordered the arrest of Syria’s President Bashar al-Assad, his brother Maher al-Assad, and two other high-ranking officials for their role in using banned chemical weapons against civilians in Syria, a judicial source said today.

The arrest orders—which accuse them of being involved in crimes against humanity and war crimes—come after a criminal investigation into chemical attacks in the town of Douma and the district of Eastern Ghouta in August 2013, attacks which killed more than 1,000 people.

It is the first time an international arrest order has been issued for the Syrian leader, whose forces crushed protests that started in 2011 with a violent crackdown that U.N. experts have said amount to war crimes.

It is also the first time international arrest orders have been issued over the chemical weapons attack in Ghouta in 2013, says Mazen Darwish, lawyer and founder of the Syrian Center for Media and Freedom of Expression (SCM), which filed the case in France.

Syria denies using chemical weapons but a previous joint investigation of the United Nations and the Organisation for the Prohibition of Chemical Weapons found that the Syrian government used the nerve agent sarin in an April 2017 attack and has repeatedly used chlorine as a weapon.

The Syrian presidency and information ministry did not respond to requests for comment.

“The president is responsible for many crimes in Syria – but with this type of weapon in particular – sarin gas – it’s impossible to ignore his role,” Darwish told Reuters, noting that the president’s approval as the head of the armed forces would be required.

French judges ordered the arrest of two former defense ministers over a 2017 blast that killed a French-Syrian man at his house in Daraa.