So far government has no power over bitcoins yet as it is on a decentralized platform and i feel it will gain more market power globally even though few countries banned them.. just like in the past when share market was introduced in the past it took lot of time for it be accepted by the public like wise its normal in the case of bitcoins aswell hence i don't think that the government has to make it illegal but it illegal in some countries to buy or trade on bitcoins as it is banned