I have to say that there is no government has the power to ban Bitcoin, the most possible thing they can do is to ban their people to use bitcoin by issuing a regulation against bitcoin. Even if they do such thing, their people will be still able to access/use bitcoin as it is an online thing unless the government ban the internet as well 
Governments have the power to legislate and that's all they need. Governments can require any transaction using bitcoin be reported and the person transferring the bitcoin can can be made to show proof of the price at which it was acquired. Put money in a checking account and the bank must issue a 1099 if a person receives any interest. Us a bitcoin anywhere in non-black market commerce and the government will have the power to regulate it. Bitcoin activity in blackmarkets can't be controlled but that may not be of much use to most people. As the US keeps issuing more and more Fiat money, bitcoin could continue to rise but, the day it is ever transferred to buy something or pay for service, capital gains taxes will be due. Engage in a transaction and do not report your gain and you are placing yourself in jeopardy. Take your chances. Do what you want but, you must know the law and know the consequences if you choose to ignore it.