Conferred powers
The EU has the powers conferred on its institutions by the Treaties. Powers not conferred remain with the member states. This is similar to provisions in the 10th Amendment of the US Constitution and to the Swiss Constitution. Powers not shifted to the federal level remain with the lower national, provincial or regional level,so that legal sovereignty is divided between the two levels.
The principle of conferral of competence by individual states on a higher entity is included in Article 1 TEU as amended by the Lisbon Treaty.