The European Directive on Strategic Environmental Assessment (SEA) provides three approaches to implementation in Member States, i.e. a case-by-case approach, a list approach, and a mixed approach. However, the European Commission appears unwilling to develop the latter two approaches, which may make the SEA Directive's scope unclear and create legal uncertainty. The aims of this article are to point out the weaknesses of the current case-by-case approach and to advocate a much clearer but underdeveloped approach, i.e. the list approach. To this end, the article will explore the issue of legal certainty in the SEA Directive, identify and resolve the challenges involved in a list approach, and finally present a step-by-step guide to developing such an approach.