Abstract The Lisbon Treaty emphasized the importance of subsidiarity control in relation to the Area of Freedom, Security and Justice (AFSJ). The article demonstrates that the types of reasoning national parliaments use to raise subsidiarity objections in the AFSJ depend less on the institutional strength of national parliaments in EU affairs and more on the institutional evolution and material scope of EU proposals. Relying on the AFSJ case, the article shows that national parliaments use a narrow legal interpretation of subsidiarity when the EU legislation threatens Member States' legal traditions and State powers. However, concerns about the respect of national legal diversity are replaced by a more political approach to subsidiarity control when politically sensitive and contentious issues are at stake.