The well-established pattern of Executive expansionism and limited oversight of Executive action in times of terrorism is problematic from the civil libertarian point of view. How to limit such action has been the subject of much scholarship, a large amount of which focuses on perceptions of institutional competence rather than effectiveness. For the authors the effective control of security-focused state action is to be judged by the extent to which it consists only of action that is necessary and proportionate and thereby strikes an appropriate balance between security exigencies and individual rights. This article, written and structured in dialectic form, presents competing perspectives on effective oversight mechanisms: on the one hand an extra-constitutionalism perspective, proposing a limited role for the Judiciary and emphasising the need for legislative and democratic controls; and on the other an argument for judicial muscularity.