This article evaluates the design of the official language policy of the Norwegian government in the field of higher education, which was set out in two white papers in 2008 and 2020. The language policy aims to avoid domain loss of the Norwegian language and thus keep it 'complete' and able to function as a unifying factor in society. In the two white papers, however, the logic of collective action in language policy is not explicit. We adopt a theoretical approach based on public policy evaluation to reconstruct the language policy's internal logic of action (i.e. its 'programme theory' or 'theory of change'). Secondly, we assess the validity of the assumptions underlying the programme theory of the two white papers in light of the criteria of plausibility, feasibility, and testability. The results show that most of the measures included in the 2008 language policy are not supported by a valid programme theory. By contrast, most of the measures in the 2020 language policy are based on a valid theory of change although several weaknesses persist. This article contributes to research on the evaluation of language policies by focusing on a relatively unexplored aspect, i.e., the evaluation of policy design.