This paper addresses some of the jurisdictional challenges in prosecuting fighters who joined the ranks of the Islamic State of Iraq and the Levant. It argues primarily in favor of prosecution by the states of which the fighters are nationals. International avenues for prosecution should be examined, as a subsidiary, in case states are reluctant to investigate crimes committed by their nationals. The paper argues in favor of prosecuting suspected ISIL fighters, by a court that respects due process of law with the aim of promoting accountability in a region constantly plagued by conflict.