Now the question is: are you still a sovereign country if you pooled your currency with N other countries that exert a common decision power through a central bank over it?
Having power over your own currency, in good or bad, is a typical attribute of being sovereign. There are minor exceptions (like Kosovo adopting euro unilaterally), but they are very untypical.
Having power over your own currency, in good or bad, is a typical attribute of being sovereign. There are minor exceptions (like Kosovo adopting euro unilaterally), but they are very untypical.