This article reviews the legal and political science literatures on the extensive interpretation of the European fundamental freedoms and on possible ways out. The common market rules were originally laid down in an international treaty, the Treaty of Rome. In functional terms, this treaty became a de facto constitution, implying that its content, including the fundamental freedoms, were constitutionalised. We review how this constitutionalisation constrains legislators at the Member State and European levels. In order to identify possible ways out, we also review several reform options: institutional reforms of the European judicial system; the de-constitutionalisation of the fundamental freedoms; counterbalancing these freedoms with further strengthened social rights; and contestation of over-constitutionalisation within the given primary law framework. We conclude that reform options are available that could gradually free the legislators from the over-constitutionalisation of the common market rules. Such options should become part of the ‘Conference on the Future of Europe’ process and debates about EU reforms in general, as more flexibility is warranted in a heterogeneous EU.