The domination of the world system by the nation-state poses a formidable challenge to modern Islamic political and juristic discourse, especially when the state is secular and non-Islamic. In this article, I examine a collective fatwā, issued a few weeks after the September 11 attacks on Washington D. C. and New York City. The fatwā gave permission to American Muslim soldiers to participate in the American military efforts against the perpetrators of the attacks, even if that involved the declaration of war against a Muslim country. By giving such permission, the fatwā implies that the principle allegiance of the American Muslim soldier is to his own country, especially in a situation of war. Issued by a group of Muslim 'ulama' and intellectuals with a Salafī-reformist background, this fatwā represents an Islamic attempt by Muslims to address some of the major changes in the world system. I also examine Muslim opposition to the fatwā, mostly from other Islamic Salafī circles, which points to a profound division within Salafism.