European constitutional identity as an implicit limit to amending EU treaties – General trend towards acknowledging implicit constraints to constitutional amendments as well as empowering supreme courts and constitutional courts to monitor ‘unconstitutional constitutional amendments’ – Substantive limits to revising EU treaties essentially based on Article 2 TEU – Conditionality mechanism rulings as a point of departure for speculating on the emergence of a European constitutional identity – ECJ’s competence to review EU treaty amendments with a self-restrained approach as a last resort mechanism.