Ofcourse, The Government can totally ban bitcoin in there country anytime they want. If they see anomalies or illegal doings because of bitcoin, ofcourse they have the power to ban it. You know what, the reason why some country already banned bitcoin? It is because of illegal happenings with the presence of bitcoin. It is widely used mode as a payment in blackmarket, illegal transactions and if this things continues maybe all countries will ban btc and btc will die.