Despite his importance as a senior Al-Qaeda spokesman, no detailed examination exists of Adam Yahiye Gadahn’s employment of fiqh al-jihad—that branch of Islamic jurisprudence regulating the lawful waging of jihad—to condemn or condone violence committed in the name of Al-Qaeda. This article first provides a detailed exposition of Gadahn’s sharia-based critique of affiliates’ conduct deemed by him in violation of Islamic law and involving the commission of major sins. Second, Gadahn’s conception of fiqh al-jihad is contextualized and contrasted with the comprehensive fiqh al-jihad-based critiques produced by respected militant Islamist scholars. A key finding here is that Gadahn (unlike these scholars) illicitly truncates the application of fiqh al-jihad with the result that he demands sharia-compliance when criticizing intra-Islamist violence yet ignores sharia-compliance when targeting America and Americans. Third, reasons are considered for this incoherent application of fiqh al-jihad and attempted Islamic legalization of anti-American mass casualty terrorist attacks. Finally, the discussion concludes with implications for counter-Al-Qaeda strategy.