Governments cant really "control" bitcoin, however they can enforce regulations. They cant really tax the transactions that take place within the bitcoin platform as the identity of each trader is unknown but once transactions leave the bitcoin platform and are traded for fiat they can be traced and the government can regulate and monitor them. By creating something that is detached from any regulating authority, it removed all control of governments and central banks and so regulation will require a well-coordinated effort across almost all economies.