In his law practice, he is best known for bringing the case of Victims of Sabra and Shatila v. Ariel Sharon et al., under the law of universal jurisdiction in Belgium, where his clients won a judgment on 12 February 2003 against the accused before a change in Belgian law removed the jurisdiction of the court. Other cases he pursued included one against Saddam Hussein, who was the object of an international campaign initiated in 1995 by Mallat with officials in Kuwait, London and Washington that developed into INDICT, a nongovernmental organisation he helped found in Britain in 1996. By 1998, INDICT had received open support in the American Congress and in the British Parliament, and was embraced by then US President Bill Clinton and British Prime Minister Tony Blair. The campaign laid the ground for a case against Saddam Hussein in Belgium in 2002, and his eventual trial in Iraq in 2005. A third case was won against Muammar Gaddafi in Beirut courts for the families of the historic leader of the Shi'i community Musa al-Sadr and his two companions, journalist Abbas Badreddin and cleric Muhammad Ya`qub, who disappeared in Libya upon their official invitation by Gaddafi in August 1978. Mallat also helped establish the Middle East regional office of Amnesty International in Beirut in 1999 for which his law firm has acted since as legal counsel. First led by directors Kamel Labidi and Ahmad Karaoud, both former prisoners of opinion in Tunisia, the regional office formed an inspiring precedent to a multitude of civil society organizations across the Middle East focusing on the promotion of human rights, accountability, and the abolition of the death penalty.