The Theory and Practice of Legislation

Both at the European and at the Member State level, evidence-based law making is on the rise. So far, the attention has mostly gone to methods of ex ante evaluation used by the legislature. In this article, we argue that more attention should be paid to the role of courts as regulatory watchdogs. The CJEU seems to move in this direction by increasingly conducting a procedural (proportionality) review of legislation. However, the CJEU does not yet scrutinise the underlying data or the scientific evidence on which consultations, impact assessments and other forms of ex ante evaluation rest. This means that when these evaluations are based on poor quality data, this will also affect the CJEU’s judgement. For Dutch courts, the situation is different. They are so far unwilling to include ex ante evaluations or empirical data in a proportionality review of legislation, although the Advisory Division of the Council of State emphasises the principles of subsidiarity and proportionality in its policy-analytical review of draft legislation. This raises the question: why do courts avoid assessing the reliability of (scientific) evidence used by legislators and regulators? Here they might learn something from the US, where the Supreme Court developed its Daubert doctrine in order to guide courts in filtering out ‘junk science’ from the law-making process.