Maybe the government is the worst choice for bitcoin? Have you ever thought about it this way?
Bitcoin was made to be decentralized and ownership of bitcoin by the government would took a large part of it from the market for free. The government can print as much money as it wants and use it to buy bitcoin to take it out of the markets and keep it from being circulated and exchanged. No bitcoin in circulation would mean no more problems for the governments who feel threatened by it. It's easier than trying to enforce a ban.