But there are limits to the effectiveness of national action. Gaps are left which only the EU can fill. In order to reach its o
bjectives, from the very outset the Treaty assigned a central role to fully-fledged common policies such as competition, trade, transport, agriculture and fisheries, and more recently EMU. There cannot be a true internal market and a customs union without precise rules to establish a level playing field. Without harmonising the great diversity of Member State policies, internal border controls would have had to be maintained, th
e EU could not have spoken ...[+++] with one voice in international trade and sustainability would have suffered in a downward spiral of negative competition.Sans une harmonisation de la grande diversité des politiques des États membres, les contrôles aux frontières intérieures auraient dû être maintenus, l'UE n'aurait pas pu parler d'une seule voix dans les échanges internationaux et sa viabilité aurait souffert d'une spirale de concurrence négative.