Treaty has created its own legal system which…became an integral part of
the legal systems of the Member States and which their courts are bound
States have limited their sovereign rights, albeit within limited
fields, and have thus created a body of law which binds both their
nationals and themselves."
executive force of Community law cannot vary from one State to another
in deference to subsequent domestic laws, without jeopardizing the
attainment of the objectives of the Treaty."