Over the past forty years states have increasingly cooperated on counter-terrorism policies. At the same time, a fear has grown that such cooperation might reduce abidance by the rule of law. While having become the conventional wisdom, it is still uncertain whether cooperation actually reduces rule-of-law abidance. Studies rarely lay out their criteria; national policies are not compared to the results of international decision-making. The paper seeks to close this gap with a comparative analysis. It is driven by a political science approach, but strongly informed by comparative law. The development of an index to measure rule-of-law abidance is one of its main contributions. The index encompasses four dimensions: observation of civil liberties, governance by parliamentary laws, guarantee of legal certainty, and provision of independent review. The paper assumes that the institutional conditions governing decision-making explain rule-of-law abidance. It analyses counter-terrorism policies made in three different institutional settings: national decision-making around 1970, intergovernmental decision-making in the late 1970s, and recent EU decision-making. It studies Germany, France and the UK. While the need to scrutinize different countries is obvious for national policy-making, it also provides useful insights for the other settings, as national implementation may have a significant impact on the final policies. The 18 cases are studied based on a content analysis using fuzzy set/QCA for the empirical measurement. The study disproves the conventional wisdom: National policies respect the rule of law least, international policy-making pays most attention to its exigencies, while the EU occupies a medium position.