A national currency is both a symbol of sovereignty and the key to the pursuit of an independent economic and budget policy.” (Feldstein, 1997, p. 3.) A special feature of European monetary union will, in fact, be that it will not have a complementary political union - at least in the foreseeable future.
The principle of “one country, one currency” runs like a thread throughout monetary history. In EMU, this link is being broken for the first time and replaced by the principle of “one market, one money”. (King, 1997a, p. 237.) From a constitutional perspective, this is certainly an unusual and historically unique event.