Shared competence
"A shared competence" would normally entail that two different decision-makers share the right to decide and make laws.
When the EU and its member states share a competence, the Member State loses its 'competence' (power to take decisions) when the EU decides to regulate. So EU legislation does not only replace the content of a national law, it also removes the national right to legislate.
Future
The Lisbon Treaty proposes in Art. 4 TFEU that the following areas become shared competences: competition rules within the internal market; the Area of Freedom, Security and Justice; agriculture and fisheries; transport; trans-European networks; energy; social policy; Economic, social and territorial cohesion; the environment; public health; and consumer protection.
Links
See also Categories of competence and Convention working group on Complementary Competence.
