Abstract—As sharing agreements are being ratified by the Federal Communications Commission (FCC) for various spectrum bands for commercial broadband use, it also opens up an equally challenging problem of enforcing these policies. The efficacy of an enforcement system greatly depends on the accuracy of evidential information and the speed of adjudication. The inherent unguided and unbounded nature of radio wave propagation, allows spectrum infractions to cause widespread damage and makes it hard to locate at the same time. On the other hand, it also lends itself to distributed methods for efficient enforcement of spectrum etiquette. We leverage omnipresent mobile users to implement a paradigm of “eye-witness” for detecting violations of spectrum policies. We design and analyze the crowdsourced enforcement architecture and show three main results: 1) It detects an infraction with a consistent high degree of accuracy (> 90%), 2) It is able to accurately locate the source of i...