If a single country decides to ban bitcoin, not only the citizens itself will suffer but even the government officials do. They will find it hard how to ban a currency which transactions are not totally visible. And bitcoin as a decentralized in nature, provides that no single entity or group is capable to ban it or shut it down.

Bitcoin cannot be banned legally but there might be restrictions along with it. And the more they see bitcoin as a hindrance to fiat, the more people will be even attached to it. Gold was banned some years ago but when it comes to bitcoin, it's better to comply than banning it.