Cooperation in counterterrorism policing increases when communities can be confident that legislation and policy is not implemented in an arbitrary or discriminatory fashion: the ability to challenge executive overstretch, abuse, or misapplication of powers is vital for maintaining procedural justice. Through examining the experiences of the Federation of Student Islamic Societies, one of the oldest British Muslim civil society organizations, we see how key structural features of the counterterrorism legal and policy framework-the wide definition of terrorism, the broad discretion in the use of stop and search powers at ports, and the expansion of Prevent into the opaque terrain of nonviolent extremism-undermine cooperation. Since 2001, government policymakers and security practitioners have recognized the need to work with individuals and organizations in Muslim communities to protect the United Kingdom against the threat of international terrorism. 1 The potential benefits of effective partnership and cooperation include the improved flow of information and intelligence to the police, a reduction in the backlash against state actions, and increased community capacity for countering violent extremism. 2 This article focuses on the legal and policy framework of counterterrorism, which shapes the terrain within which partnerships are negotiated and trust is built. Careful calibration is needed to ensure that broad legal powers and policies support rather than undermine cooperation and partnership with community organizations. Research on cooperation between the public and the police finds strong and consistent links between public willingness to cooperate and evaluations of the legitimacy of the police. Such legitimacy is shaped by experiences and expectations of procedural fairness. 3 Furthermore, evaluations of procedural justice link to social group identity; thus, it is not only how an individual is treated that impacts their evaluation of procedural fairness, but how others belonging to their social group and community organizations representing that group are treated. 4 Key features of fairness include the application of policies and rules in a way that is seen to be consistent and transparent. Such transparency and consistency is important in avoiding the perception that rules are applied on the basis of personal prejudice or bias but are instead seen to be the result of the application of objective information and criteria. 5 The CONTACT Tufyal Choudhury