Proportionality is a key principle of EU law. However, in spite of procedural requirements intended to ensure the full integration of proportionality as a design principle in EU law, the European Union continues to pass disproportionate counterterrorism laws. If proportionality is a fundamental constitutional principle of the European Union, and if lawmaking processes at EU level have been designed expressly with this in mind, then why do the EU’s counterterrorism laws consistently raise issues of disproportionate interference with rights? Taking as a case study the passage of the EU Directive on Combating Terrorism, this article argues that at least part of the answer lies in the curtailment and adjustment, in the counterterrorism field, of lawmaking processes that are designed to be participatory, evidence-based, and informed by proportionality.