Authorities in France detained a former prime minister of Kosovo on Wednesday on a Serbian warrant that accuses him of war crimes. Ramush Haradinaj, who served as a guerrilla commander during the Kosovo war, was taken into custody upon his arrival at Basel-Mulhouse airport over the 2004 arrest warrant. Serbia considers Haradinaj a war criminal for his activities in the 1998-1999 conflict, when he was accused of targeting Serbs, Albanians, and Romani. He was tried and acquitted twice by a United Nations court in the Hague on the charges. Kosovo’s foreign ministry has called his arrest “unacceptable,” and French authorities are reportedly examining whether or not the charges in the warrant differ from those on which he was already acquitted. Haradinaj, the leader of Kosovo’s Alliance for the Future of Kosovo Party, was traveling on a diplomatic passport when he was arrested. A similar arrest by Slovenia in 2015 saw the politician released after two days in custody.