 In Khartoum, he travelled to Hilat Koko with Jamal al-Fadl in late 1993 or early 1994, and met with Amin Abdel Marouf to discuss chemical weapons.He is also credited by al-Fadl's testimony with a 1992 fatwa issued at the request of Al Qaeda leadership, described as pivotal in al-Qaeda's development as it provided the group with justification for the killing of Muslim civilians and bystanders in the course of killing Americans and other non-Muslim enemies.The fatwa is putatively based on one by the influential 14th-century Salafi scholar Ibn Taymiyyah ("Ibn al Tamiyeh") permitting the killing of Muslim supporters of the "Tartars" (Mongols) who threatened to invade the Mamluk Sultanate in Egypt.