Principle of conferral
The principle of conferral is a fundamental principle of European Union law. According to this principle, the EU is a union of member states, and all its competences are voluntarily conferred on it by its member states. The EU has no competences by right, and thus any areas of policy not explicitly agreed in treaties by all member states remain the domain of the member states.
This principle has always underpinned the European Union, but it is explicitly specified for the first time in the proposed new Treaty establishing a constitution for Europe.
See also Tenth Amendment to the United States Constitution.