But there are limits to t
he effectiveness of national action. Gaps are left which only the EU can fill. In order to reach its objectives, 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 t
o establish a level playing field. Without harmonising the great diversity of Member State policies, inter
nal border controls ...[+++]would have had to be maintained, the EU could not have spoken with one voice in international trade and sustainability would have suffered in a downward spiral of negative competition.