To be honestly, i dont think a government can ban (to be more precisely: has the right to ban) a "virtual currency" which isnt even a real currency..
Just because people treat it like a currency it still isn't one.
If a government could ban Bitcoin, they also could ban mathematic equations and hash functions.
But back to topic:
Bitcoins can't be frozen as long as there are enough miners with electricity
Bitcoin can be frozen if there are too many crime reports of transactions in a country. This is also true if many bitcoin exchange market becomes insolvent, all members can pursue a lawsuit, and government can use financial laws. There is currently no state to do so, governments tend not responsible. But they continued to conduct surveillance.
Miners are not related to frozen, they are same as smartphone operating system developer. government only focuses on model, report, and level of market transactions.