A legalistic interpretation of Islam refers to how believers interpret their rights and obligations in relation to Islam’s holy texts. An individual who has a legalistic interpretation of the faith has adopted a rules-based approach to the religion, in which the Qur’an and sunnah provide strict guidelines—not just for the practice of the faith, but also for virtually every aspect of one’s daily life. This legalistic interpretation will be manifested externally. For individuals to be regarded as having a legalistic interpretation for the purposes of this study, they had to go far beyond following the basic rules that most or all Muslims agree upon, such as prayer five times a day or refusing to eat pork. We were looking for individuals who followed even seemingly obscure religious rules and practices.

It is worth noting that a person exhibiting a legalistic interpretation of Islam is not necessarily radical, or radicalizing: it may simply be indicative of a conservative practice of the faith. A large number of Muslims who could in no way be considered dangerous have adopted a legalistic understanding of Islam. However, one can see how for Gadahn a legalistic understanding blended into the rest of his radicalization. Some literature that has been distributed in the United States reinforces this connection. In Muhammad bin Jamil Zino’s Islamic Guidelines for Individual and Social Reform, for example, the author outlines many legalistic rules for religious life: warning the reader against the sinfulness of music, photographs, and women who laugh in the streets. Interspersed with these injunctions are exhortations to violence, such as the statement that “Jihad is obligatory on every Muslim in two ways: by spending one’s wealth or offering oneself for fighting in the cause of Allah.” As it was for Gadahn, Zino’s text naturally blends the rules that one is supposed to follow into the supposed religious obligation to undertake violence to advance the faith.

About half of the homegrown terrorists examined in this study exhibited this aspect of the radicalization process: of the 117 individuals surveyed, 57 (48.7%) had adopted a legalistic interpretation. The rates of adopting a legalistic interpretation are similar in the U.S. and U.K. We could only determine that individuals had not embraced a legalistic interpretation in four cases.

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. . . . As homegrown terrorists internalize rigid interpretations of Islam, many come to view any alternate interpretations and practices as not just incorrect theologically, but as a personal affront. In this way, any disagreement about religion is personalized, and may be met with a great amount of vitriol. This intolerance of perceived deviance is usually expressed verbally, through the chastisement of other Muslims—but there have also been instances where this intolerance manifests in violence, as when Adam Gadahn punched Haitham Bundakji in the face.

Because the evidentiary bar for this step is rather high (there had to be an outward manifestation, such as the berating of other Muslims), the percentage of individuals in whom it was identified is comparatively low: just 17.1% definitively went through this step. But since the evidentiary bar was high, we think that the fact it manifested in more than one out of six of the individuals studied is significant. There were only four cases in which we could determine that this step was not present.

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