You can keep your bitcoin through a hard wallet or even in electrum wallet.

When a country banned bitcoin, they usually ban transactions only, so your transactions cannot be legal but you can always keep it and bring it anywhere you go. I'm sure on some countries like China, altough they ban bitcoin trading but I'm sure there are some people who are holding bitcoin because it's possible, the only way to stop people from holding bitcoin is when the government ban the internet, which is impossible.