Despite their best efforts to counter violent extremism (CVE), neither law enforcement nor intelligence agencies can be everywhere at all times. Furthermore, many potentially worrisome behaviors (e.g., expressing sympathy for a terrorist-labeled group) are not necessarily illegal; thus, intervening through arrests is often not an acceptable option in most western societies. This highlights that radicalization, and any associated level of risk for committing violence, are not dichotomous, but exist on a continuum (Sedgwick, 2010). Therefore, interventions with individuals occupying different points along such a spectrum call for different approaches to mitigating that risk (Klinke & Renn, 2002). Additionally, given the low per capita base rate of terrorists, and self-selection biases that would tend to dissuade those in favor of extremist ideologies from choosing to participate in a presumably wide range of CVE programs, the odds of would-be violent extremists volunteering to participate in CVE programs—much less, subsequently diverting themselves from malevolent trajectories—is slim (Black, 2004).
Williams, Michael J., John G. Horgan and William P. Evans. 2015. "Research Summary: Lessons from a US Study Revealing the Critical Role of "Gatekeepers" in Public Safety Networks for Countering Violent Extremism." In Countering Violent Extremism: Developing an Evidence-base for Policy and Practice, eds. Sara Zeiger and Anne Aly. Perth: Curtin University, 139-143. https://www.nla.gov.au/sites/default/files/webform/draft_cve_developing_an_evidence-based_for_policy_and_practice.pdf#page=145