The principle of subsidiarity as construed by the Court of Justice and the Advocates General (AG) is not an autonomy clause. Article 5(3) Treaty on the European Union (TEU) aims to promote the efficiency of governance rather than the autonomy of the Member States (MSs) and of the subnational governments. Although a number of scholars emphasize the potential role of federal proportionality for the protection of the autonomy, the effectiveness of this principle is limited in practice due to the Court’s judicial self-restraint. In the EU the autonomy of national and subnational governments is protected primarily by the legal bases in the Treaty. The reasoning of the Court to delimit these legal bases largely overlaps with and absorbs considerations of subsidiarity that acquire a merely ancillary role.